Echelon LONWORKS PLT-22 User Manual

LONWORKS®

PLT-22 Power Line Transceiver

User’s Guide

(110kHz – 140kHz Operation)

Version 1.2

@ ECHELON

C o r p o r a t i o n

078-0175-01C

®

Echelon, LON, LONWORKS, LonBuilder, NodeBuilder, LonManager, LonTalk,
L

ONMARK, Neuron, 3120, 3150, the LonUsers logo, the LONMARK logo, and

the Echelon logo are trademarks of Echelon registered in the United States
and other countries. LonPoint, LonSupport, and LonMaker are trademarks
of Echelon Corporation.

Other brand and product names are trademarks or registered
trademarks of their respective holders.

Neuron Chips, Power Line products, and other OEM Products were not
designed for use in equipment or systems which involve danger to
human health or safety or a risk of property damage, and Echelon
assumes no responsibility or liability for use of the Neuron Chips or Power
Line products in such applications.

Parts manufactured by vendors other than Echelon and referenced in
this document have been described for illustrative purposes only and
may not have been tested by Echelon. It is the responsibility of the
customer to determine the suitability of these parts for each
application.

ECHELON MAKES AND YOU RECEIVE NO WARRANTIES OR CONDITIONS,
EXPRESS, IMPLIED, STATUTORY OR IN ANY COMMUNICATION WITH YOU,
AND ECHELON SPECIFICALLY DISCLAIMS ANY IMPLIED WARRANTY OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

No part of this publication may be reproduced, stored in a retrieval
system, or transmitted, in any form or by any means, electronic,
mechanical, photocopying, recording, or otherwise, without the prior
written permission of Echelon Corporation.

Printed in the United States of America.
Copyright ©1996 - 2002 by Echelon Corporation.

Echelon Corporation
www.echelon.com

Contents

1 Introduction 1-1

Audience 1-6
Content 1-6
Related Documentation 1-6

2 Using the PLT-22 Transceiver 2-1

Mechanical Dimensions 2-2
PLT-22 Transceiver Pinout 2-3
PLT-22 Transceiver Electrical Specifications 2-4
External Components 2-6
Crystal 2-6
Power Supply Bypassing and Grounding 2-7
Band-in-Use (BIU) and Packet Detect (PKD) LED Connections 2-7
Neuron
Transmit Output Level 2-10
TXON Output Signal 2-10
Application Schematic: Neuron 3150® Chip 2-11
Application Schematic: Neuron 3120

3 PLT-22 Transceiver Programming 3-1

Dual Carrier Frequency Mode 3-2

CENELEC Access Protocol 3-3

Power Management 3-3
Standard Transceiver Types 3-4
LonBuilder
Channel Definitions

4 Coupling Circuits 4-1

Power Line Communications 4-2
Coupling Techniques 4-4
Power Line Coupling Basics 4-4
Power Line Coupling Details 4-8
Safety Issues 4-11
Safety Isolation Considerations 4-11
Ground Leakage Currents 4-13
Capacitor Charge Storage 4-13
Line Surge Protection 4-13
Fuse Selection 4-16
Recommended Coupling Circuit Schematics 4-16
Example 1: Line-to-Neutral, Non-Isolated Coupling 4-18
Example 2: Line-to-Neutral, Transformer-Isolated Coupling 4-20
Example 3: Line-to-Earth, Non-Isolated Coupling 4-22
Example 4: Line-to-Earth, Transformer-Isolated Coupling 4-24

®

Chip Connections 2-8

®

Chip 2-12

®

and NodeBuilder® PLT-22 Transceiver 3-6

LONWORKS PLT-22 Transceiver User’s Guide i

5 Power Supplies for the PLT-22 Transceiver

Introduction 5-2
Power Supply Design Considerations 5-2
Power Supply-Induced Attenuation 5-2
Power Supply Noise 5-3
Energy Storage Power Supplies 5-3
Energy Storage Capacitor-Input Power Supplies 5-5
Capacitor-Input Power Supply Schematic 5-7
Energy Storage Linear Supplies 5-8
Traditional Linear Power Supplies 5-9
Switching Power Supplies 5-9
Power Supply-Induced Attenuation 5-9
Noise at the Power Supply Input 5-12
Switching Power Supply Frequency Selection 5-12
Switching Power Supply Input Noise Masks 5-12
Switching Power Supply Output Noise Masks 5-17
Options 5-21
Pre-designed Switching Supplies 5-21
Off-the-Shelf Switching Supplies 5-22
Custom Switching Supplies 5-22

5-1

6 Design and Test for Electromagnetic Compatibility 6-1

EMI Design Issues 6-2
Designing Systems for EMC (Electromagnetic Compatibility) 6-2
ESD Design Issues 6-4
Designing Systems for ESD Immunity 6-4
Conducted Emissions Testing 6-6

7 Communication Performance Verification 7-1

Why Verify Communication Performance? 7-2
Verification Strategy 7-2
Power Line Test Isolator 7-3
Test Equipment 7-4
Good Citizen Verification 7-6
Unintentional Output Noise Verification 7-6
Excessive Loading Verification 7-7
Transmit Performance Verification 7-10
Receive Performance Verification 7-11
Packet Error Measurement with Nodeutil 7-11
Verification Procedure 7-12

8 References 8-1

Reference Documentation 8-2

Appendix A PLT-22 Transceiver Isolation Transformer A-1
Specifications

PLT-22 Transceiver Isolation Transformer Schematic A-2
PLT-22 Transceiver Isolation Transformer Electrical A-2
Specifications
PLT-22 Transceiver Isolation Transformer Vendors A-3

ii Echelon

Appendix B PLT-22 Transceiver-Based Node Checklist B-1

PLT-22 Transceiver-Based Node Checklist B-2
PLT-22 Transceiver and Neuron Chip Connections B-2
PLT-22 Transceiver Programming B-4
PLT-22 Transceiver Coupling Circuit General B-4
PLT-22 Transceiver Coupling Circuit Components Key B-5
Specifications
PLT-22 Transceiver Power Supply - General B-6
PLT-22 Transceiver Power Supply - Switching Type B-6
EMI & ESD Design B-7
Product Qualification - EMC B-8
Product Qualification - Electromagnetic Immunity and B-8
Communication Performance

Appendix C External Power Supplies with Integrated

Coupling Circuits C-1

Vendors for External Power Supplies w/ Integrated Coupling Circuits C-2

LONWORKS PLT-22 Transceiver User’s Guide iii

iv Echelon

1

Introduction

The PLT-22 Power Line Transceiver provides a simple, cost-effective
method of adding LONWORKS® power line technology to any control
system. Network data are broadcast through the power mains,
eliminating the need for dedicated wiring and greatly reducing
installation costs. A replacement for Echelon's popular PLT-21 Power
Line Transceiver, the PLT-22 transceiver also includes several new
features to significantly improve communications reliability and lower
node cost.

LONWORKS PLT-22 Transceiver User’s Guide 1-1

Intermittent noise sources, impedance changes, and attenuation make the power line
a hostile signal path. The PLT-22 transceiver operates reliably in this harsh
environment through a novel dual carrier frequency capability as well as custom
digital signal processing which provides adaptive carrier and data correlation,
impulse noise cancellation, tone rejection, and low-overhead error correction. These
innovations permit the transceiver to operate reliably in the presence of consumer
electronics, power line intercoms, motor noise, electronic ballasts, dimmers, and
other typical sources of interference.

Each PLT-22 transceiver operates as a backward compatible replacement for the
PLT-20 and PLT-21 transceivers when used with previous versions of configuration
parameters. In this mode, all transmissions can be received by any PLT-20, PLT-21,
or PLT-22 transceiver.

When used with new transceiver configuration parameters, the dual carrier
frequency mode of the PLT-22 transceiver is activated. In this mode, PLT-22 based­nodes are able to communicate even when the primary frequency range (125kHz ­140kHz) is blocked by noise. With dual frequency mode, a PLT-22 transceiver begins
each transaction by sending backward compatible packets. If impairments prevent
communication in this frequency range, the PLT-22 node will automatically switch
carrier frequencies in order to complete the transaction with other PLT-22 based
nodes.

The PLT-22 transceiver complies with FCC, Industry Canada, Japan MPT, and
European CENELEC EN 50065-1

1

regulations for signaling in the 125kHz-to­140kHz and 95kHz-to-125 kHz frequency bands. The transceiver implements the
CENELEC access protocol, which can be enabled or disabled by the user. By
incorporating the access protocol into the power line transceiver, Echelon has
eliminated the need for users to independently develop the complex timing and
access algorithms mandated by the CENELEC EN 50065-1 regulation. The PLT-22
transceiver also is compliant with the Electronic Industries Association Standard
EIA-709.2.

The transceiver's power amplifier includes a selectable 3.5V peak-to-peak (p-p) or 7V
p-p mode for maximum communication performance. The 1Ω output impedance and
1A p-p current capability of the amplifier allow it to drive high output levels into low
impedance circuits, while the highly efficient design draws less total current than
previous transceivers.

The PLT-22 transceiver is powered by user-supplied +8.5 to +16VDC and +5VDC
power supplies. The wide supply range is a key benefit when designing inexpensive
power supplies. If a battery-backed power supply is used, the transceiver will
continue signaling even during a power failure on the power mains.

The PLT-22 transceiver incorporates a power management feature that constantly
monitors the status of the node's power supply. If during transmission the power
supply voltage falls to a level that is insufficient to ensure reliable signaling, the
transceiver tells the Neuron Chip to stop transmitting until the power supply voltage
rises to an acceptable level. This allows the use of a power supply with 1/3 the
current capacity otherwise required (100mA versus 300mA). The net result is a
reduction in the size, cost, and thermal dissipation of the power supply. Power
management is especially useful for high volume, low cost consumer products such as
electrical switches, outlets, and dimmers.

1-2 Introduction

The PLT-22 transceiver uses a low-cost external coupling circuit and can
communicate over virtually any AC or DC power mains, as well as unpowered
twisted pair. The PLT-22 transceiver can use all of the same coupling circuits as the
PLT-21 transceiver.

The PLT-22 transceiver is supplied as a miniature uncoated Single In-Line Package
(SIP) which can be mounted on or inside an OEM product, directly adjacent to the
Neuron Chip with which it is used. The PLT-22 transceiver maintains drop-in pin
compatibility with the PLT-20 and PLT-21 transceivers while at the same time
providing smaller package dimensions to more easily fit into tight enclosures. When
connected to an external crystal, the transceiver can supply either a 1.25, 2.5, 5, or
10MHz clock signal for the Neuron Chip, eliminating the need for a separate Neuron
Chip crystal.

The transceiver communicates at a raw bit rate of 5kbps. With the CENELEC
protocol disabled, the transceiver has a maximum packet rate of 20 packets per
second. With the CENELEC protocol enabled, the transceiver has a maximum
throughput of 18 packets per second. This high throughput makes the transceiver
well suited for residential, commercial, and industrial automation applications.

For commercial and industrial applications in high rises, manufacturing plants,
utility substations, and other large facilities, the PLT-22 transceiver can be used
with Echelon's PLA-21 Power Line Amplifier. Capable of transmitting a 10Vp-p
signal with 2Ap-p current drive, the PLA-21 amplifier is ideal for driving multiple
phase coupling circuits, high attentuation power circuits, and very low impedance
loads near circuit breaker panels and distribution transformers.

This guide describes the use of the PLT-22 transceiver in the 110kHz to 140kHz
frequency range. The PLT-22 transceiver also supports communication in the
CENELEC utility band (European A-band from 70 to 95kHz) when the transceiver is
used with a different external crystal and modified coupling circuit. For CENELEC
utility applications, refer to the companion user’s guide, Using the L

22 Power Line Transceiver in European Utility Applications.

ONWORKS PLT-

LONWORKS PLT-22 Transceiver User’s Guide 1-3

GND

CKOUT

CKSEL1

CKSEL0

XIN

XOUT

PKD

BIU

RXIN

RXCOMP

TXLVL

TXOUT

CP0

CP1

CP2

CP4

~RESET

GND

GND

V

A

V

DD5

RX

FRONT

END

A/D

TX
AMP/
FLTR

DSP

D/A

Figure 1.1 PLT-22 Transceiver Block Diagram

The compact PLT-22 transceiver must be mounted using hand or wave soldering and
requires only the addition of a Neuron 3120

®

Chip or Neuron 3150® Chip, crystal, power
line coupling network, power supply, and application electronics to build a complete node
(figure 1.2).

User's
Application
Electronics

1-4 Introduction

11

Neuron

Chip

V

DD5

Transceiver

V

A

PLT-22

Coupling

Circuit

Power Supply

Figure 1.2 Typical PLT-22 Transceiver-Based Node

Power
Mains

The PLT-22 transceiver meets the regulations for AC mains signaling of the FCC
(Federal Communication Commission), Industry Canada (formerly DOC), CENELEC
(European Committee for Electrotechnical Standardization), and Japanese MPT
(Ministry of Post and Telecommunications).

Under FCC Section 15.107 "Limits for carrier current systems," as well as Industry
Canada guidelines, communication frequencies are allocated as shown in figure 1.3.
To protect aircraft radio navigation systems operating between 190kHz and 525kHz,

restrictions on power line communication above 185kHz are being considered
PLT-22 transceiver avoids interfering with these systems by signaling in the
frequency range of 110kHz to 140kHz.

PLT-22
Transmit
Signals

General
Use

Restrictions Under

Consideration

Restricted

7

. The

100kHz 200kHz 300kHz 400kHz 500kHz 600kHz 700kHz

Figure 1.3 FCC and Industry Canada Frequency Allocation

Under CENELEC EN 50065-1 “Signaling on low-voltage electrical installations in the
frequency range 3kHz to 148.5kHz” Part 1 “General requirements, frequency bands
and electromagnetic disturbances," communication frequencies are allocated as shown
in figure 1.4. When used with a 10MHz crystal, the PLT-22 transceiver signals in
CENELEC C and B bands and implements the access protocol as specified in
CENELEC EN 50065-1 (see CENELEC Access Protocol section in Chapter 3 for more
information). For operation in the CENELEC A-band, refer to Using the L

PLT-22 Power Line Transceiver in European Utility Applications.

ONWORKS

LONWORKS PLT-22 Transceiver User’s Guide 1-5

Band Designations:

PLT-22 with

70 - 95kHz Operation

"A"

{

PLT-22 with

110 - 140kHz Operation

{

"B"

"C" "D"

Electricity Suppliers

Audience

This document is intended for designers of products using the PLT-22 Power Line
Transceiver.

Content

This manual provides detailed operating instructions for the PLT-22 transceiver.

Electricity Suppliers

and Their Licensees

PLT-22
Secondary
Signal

20kHz 40kHz 60kHz 80kHz 100kHz 120kHz 140kHz 160kHz

Figure 1.4 CENELEC Frequency Allocation

PLT-22
Primary
Signal

No Protocol

Consumer Use

PLT-22

PLT-22
Secondary

Secondary
Signal

Signal

Consumer Use

PLT-22
Primary
Signal

No Protocol

With Protocol

Restricted

Consumer Use

Related Documentation

The following documents are suggested reading:

PLT-22

PLCA-22 Power Line Communication Analyzer User’s Guide (078-0147-01)

PLA-21 Power Line Amplifier Specification and User’s Guide (078-0161-01)

Centralized Commercial Building Applications with the L
Transceiver (005-0056-01)

Demand Side Management with the L

(005-0070-01)

Using the L
Applications (078-0180-01)

1-6 Introduction

Power Line Transceiver data sheet (003-0250-01)

ONWORKS PLT-22 Power Line Transceiver in European Utility

ONWORKS PLT-21 Power Line

ONWORKS Power Line Transceivers

LONWORKS Custom Node Development (005-0024-01)

L

ONMARK

L

ONMARK Application Layer Interoperability Guidelines (078-0120-01)

®

Layers 1-6 Interoperability Guidelines (078-0014-01)

Neuron Chip Data Book as published by Motorola and Toshiba

LONWORKS PLT-22 Transceiver User’s Guide 1-7

1-8 Introduction

2

Using the PLT-22 Transceiver

This chapter describes the mechanical and electrical characteristics of
the PLT-22 transceiver along with the interface to a Neuron Chip and
external circuitry requirements. Typical application schematics are
included.

LONWORKS PLT-22 Transceiver User’s Guide 2-1

Mechanical Dimensions

Figure 2.1 presents the mechanical dimensions of the PLT-22 transceiver.

The PLT-22 is produced as an uncoated SIP (in contrast to the coated PLT-20 and
PLT-21 transceivers).

Figure 2.1 PLT-22 Transceiver Dimensions

Note: If a socket is required for prototype purposes, a Mill-Max #317-93-121-41-005
connector may be used. For more information, contact:

Mill-Max Manufacturing Corporation
190 Pine Hollow Road
Oyster Bay, New York, 11771
Telephone: [phone]
Fax: [phone]
Internet: http://www.mill-max.com

2-2 Using the PLT-22 Transceiver

PLT-22 Transceiver Pinout

Table 2.1 lists the functions of the PLT-22 transceiver pins.

Table 2.1

Pin # Pin Name Function

1 RXCOMP Connection to receive compensation component
2 RXIN Receive signal input from line coupling circuit
3 GND Ground
4 CP4 Frame clock synchronization from Neuron Chip (FCLK)
5 CP2 Bit clock synchronization from Neuron Chip (BCLK)
6 CP1 Transmit data and configuration from Neuron Chip (TXD)
7 CP0 Receive data and status to Neuron Chip (RXD)
8 GND Ground
9 V

10 CKOUT Buffered CMOS clock output: 10, 5, 2.5 or 1.25 MHz
11 CKSEL0 Selects frequency of CKOUT—see table 2.4
12 CKSEL1/TXON Selects frequency of CKOUT—see table 2.4 / TXON (supports

13 ~RESET Reset input from Neuron Chip
14 BIU CENELEC Band-In-Use indication output
15 PKD Packet detect indication output
16 TXOUT Transmit signal output to line coupling circuit
17 GND Ground
18 XIN 10MHz oscillator input
19 XOUT 10MHz oscillator output
20 VA Analog power supply input

21 TXLVL Transmit level selection input

+5VDC power supply input

DD5

PLA-21 Power Line Amplifier)

PLT-22 Transceiver Pinout

LONWORKS PLT-22 Transceiver User’s Guide 2-3

PLT-22 Transceiver Electrical Specifications

Table 2.2 lists the electrical specifications of the PLT-22 transceiver when used in
the 110kHz – 140kHz frequency range. All specifications apply over the full
operating temperature and supply voltage ranges unless otherwise indicated.

Table 2.2

Parameter Min Typ Max Units

Operating temperature range1
V

input supply voltage 4.75 5 5.25 Volts

DD5

VA input supply voltage

TXLVL = open 8.5 9.7 16 Volts
TXLVL = GND2

I

input supply current (not including PKD and BIU LED Current)

DD5

receive 16 23 mA
transmit 13 18 mA
IA input supply current

receive 4 6 mA
transmit 130 250 mA
TXOUT signal level: TXLVL=open, into 50Ω load 3.6 Volts p-p
TXOUT signal level: TXLVL=GND, into 50Ω load 7 Volts p-p
Output current limit 1.0 Amps p-p
Output impedance, in-band (transmit) 0.9 1.1 Ohms
Input impedance, in-band (receive) 500 Ohms
PKD output source current @ V

BIU output source current @ V
Power management, lower threshold 7.2 7.9 8.5 Volts

Power management, upper threshold 11.1 12.0 12.9 Volts

PLT-22 Transceiver Electrical Specifications

-40 +85 ° C

11.4 12.0 16 Volts

-0.6 V 8 mA

DD5

-0.6 V 8 mA

DD5

Notes:

1. Maximum operating temperature is a function of VA supply voltage and the maximum
transmission duty cycle for the node. A maximum operating temperature of 85°C is

specified for a V

A

the maximum achievable with LONMARK interoperable transceiver parameters and
messages of ≤34 Bytes. For other cases see figure 2.2.

2. While operating in the 7V p-p mode (TXLVL = GND), the V

11.4V under conditions of typical line voltage, room temperature, and typical current drain
(including the PLT-22 transceiver’s typical IA transmit current of 130mA). This condition

ensures adequate transmit amplifier headroom to drive the full 7Vp-p signal

2-4 Using the PLT-22 Transceiver

supply ≤12.6V and a maximum transmit duty cycle of 65%, which is

supply must not drop below

A

onto typical lines. Under worst case conditions, the minimum VA supply voltage may be

relaxed if the following additional condition is met. With worst case power supply
loading (including PLT-22 I

= 250mA), worst case component tolerances, worst case line

A

voltage, and worst case temperature, VA must remain greater than or equal to 9.0V.
This condition ensures adequate transmit amplifier headroom when driving low

impedance power lines.

When using an energy storage type power supply refer to Chapter 5 for additional timing
requirements on the above conditions.

85
80

75

VA Max =12.6V

70

65

60

55

50

VA Max =16V

45

40
35

Maximum possible transmit duty cycle
using LONMARK interoperable

30

Maximum Operating Temperature (°C)

25

transceiver parameters and messages
Š34 bytes

10%

20%

30%

40%

50% 60%

70%

80% 90%

Transmit Duty Cycle

Figure 2.2 PLT-22 Transceiver Maximum Operating Temperature vs. Transmit Duty Cycle

100%

LONWORKS PLT-22 Transceiver User’s Guide 2-5

External Components

Crystal

The PLT-22 transceiver requires the connection of an external 10.0000MHz crystal.
The crystal connects directly to two pins of the PLT-22 transceiver, with no other
oscillator components being required external to the transceiver. The crystal should
be mounted as close as possible to the transceiver to minimize parasitic effects. The
traces connecting the crystal to the transceiver preferably should be less than 10mm
(0.4") in length, and under no circumstances can they exceed 20mm (0.8") in length.

In addition to the nominal frequency specification of 10.0000MHz, the crystal should
be a parallel resonant type with a load rating of 13 to 20pF (series resonant crystals
should not be used). The frequency accuracy of the oscillator must be held to ±200
ppm over the full temperature range of operation. The PLT-22 oscillator design is
centered for the use of a crystal with a 16pF load rating. If a 13pF crystal is used,
the nominal frequency of oscillation will be 30 to 55ppm low, leaving 145ppm
available for crystal accuracy, temperature, and aging. If a 20pF crystal is used, the
nominal frequency will be 50 to 85ppm high, leaving 115 ppm for accuracy,
temperature, and aging.

While the PLT-22 transceiver design is centered around the use of a crystal whose
load capacitance rating is 16pF, it is possible to recenter the design for a crystal
whose load capacitance rating is higher than 16pF. The PLT-22 transceiver
effectively contains two 32pF capacitors, one from XIN to ground and one from
XOUT to ground. Note that the series combination of the two capacitors equals the
load capacitance of the recommended crystal. Recentering the design for the use of a
crystal with a higher load capacitance specification requires the addition of two
external capacitors whose series equivalent capacitance is equal to the load
capacitance specification of the crystal less 16pF. For instance, to use a crystal with
a load capacitance specification of 30pF, the operating frequency can be centered by
adding two 27pF capacitors, one from XIN to ground and one from XOUT to ground.

If a 10.0000MHz ±200ppm 0-5V clock signal is already available as part of the node
hardware then it may be used as a clock source for the PLT-22 transceiver by
connecting it to Pin 18 (XIN) of the transceiver. In this instance pin 19 (XOUT) of
the PLT-22 should be left unconnected. With this option, appropriate high speed
clock distribution techniques must be strictly followed in order to ensure that a clean
clock signal is present at the XIN pin of the PLT-22 transceiver.

Oscillator frequency accuracy should be checked during the design verification phase
of every PLT-22 based product. Frequency accuracy should be measured by using a
frequency counter connected to the CKOUT pin to compare the frequency of that pin
to the selected value (i.e., 10, 5, 2.5, or 1.25MHz). Be sure that no instruments or
extra cabling are connected to either the XIN or XOUT pins of the PLT-22 since even
2pF of extra load on either pin will significantly change the oscillator frequency.

2-6 Using the PLT-22 Transceiver

Power Supply Bypassing and Grounding

The PLT-22 transceiver requires the connection of external bypass capacitors. The
bypass capacitors should be placed as close as possible to the PLT-22 transceiver,
and low-impedance ground and supply traces should be used between the PLT-22
transceiver and the bypass capacitors. In addition to the bypass capacitors specified

for the Neuron Chip (see Neuron Chip Data Book
the V

and VA bypass capacitors are, as follows:

DD5

2,3,18

), the recommended values of

: None required if the V

V

DD5

supply at the PLT-22 transceiver pin 9

DD5

meets the noise masks described in Chapter 5. It is recommended
that PCB designs initially incorporate a 10µF 10V tantalum capacitor
and a 0.1µF ceramic capacitor on the V

suppy. These capacitors

DD5

can be eliminated if the design meets the noise masks in Chapter 5
and passes the receive performance tests described in Chapter 7
without the capacitors installed.

VA: 120µF (minimum) 16V, low-ESR (<0.3Ω @ 100kHz), high-frequency

aluminum electrolytic capacitor. Low ESR is required in order to
minimize VA ripple voltage when the transceiver drives low

impedance loads, drawing several hundred milli-Amperes of peak-to­peak ripple current. Note that the VA bypass capacitor is an integral

part of the mains surge protection circuitry described in Chapter 4.
In particular, the coupling circuits of Chapter 4 require the use of an
aluminum electrolytic type capacitor with a voltage rating of 16V.
Higher or lower voltage ratings will likely result in surge immunity
which is significantly below the verified levels documented in
Chapter 4.

The PLT-22 transceiver provides three ground pins. For proper operation,
all three pins must be connected to ground with low-impedance traces, or
to a ground plane between the transceiver and the Neuron Chip.

Band-In-Use (BIU) and Packet Detect (PKD) LED Connections

The PLT-22 transceiver supplies two output signals, PKD and BIU, that are
intended to drive low-current light-emitting diodes (LEDs). Both signals are active­high and must be connected to separate LEDs, with series current-limiting resistors
added between the LEDs and ground.

A Band-In-Use detector, as defined under CENELEC EN 50065-1, must be active
whenever a signal that exceeds 80dBµVrms anywhere in the frequency range

131.5kHz to 133.5kHz is present for at least 4ms. The Band-In-Use detector is
defined by CENELEC EN 50065-1 as part of the CENELEC access protocol. The
PLT-22 transceiver incorporates the CENELEC access protocol, and the PLT-22
transceiver may be programmed to enable or disable its operation. (See CENELEC
Access Protocol in Chapter 3 for more information.) When the PLT-22 transceiver is
programmed such that the CENELEC access protocol is enabled, the BIU signal is
active high whenever the CENELEC-defined conditions for Band-In-Use are met.
When the transceiver is programmed such that the CENELEC access protocol is

LONWORKS PLT-22 Transceiver User’s Guide 2-7

disabled, the threshold for the BIU signal is increased to 84dBµVrms to reduce the
possibility that power mains noise activates the BIU indicator. When the CENELEC
access protocol is disabled, an active BIU signal does not prevent the PLT-22
transceiver from transmitting. Connecting the BIU signal to an LED is most useful
when the CENELEC access protocol is enabled, since in this case the BIU signal
indicates when the PLT-22 transceiver's transmissions are restricted.

The PKD signal is active whenever a valid LonTalk
PLT-22 transceiver. The receive sensitivity of the transceiver is considerably greater
than that of the BIU indicator. The PKD signal will go active when the PLT-22
transceiver receives packets whose signal level is as small as 36dBµVrms. Thus it is
not uncommon for the PKD indicator to signal that a packet is present without the
BIU indicator turning on; this occurs in cases where the received packet signal
strength is less than the BIU threshold.

Both the BIU and PKD signals are driven directly by the PLT-22 transceiver’s DSP
processor. ESD protection diodes should be connected to these pins in applications
where the BIU and PKD signals drive LEDs that could be subject to ESD exceeding
2kV. In applications where the LEDs are surrounded by a metallic ground plane,
such as a hole in a grounded metal enclosure, the ESD diodes may not be necessary.
However, if a plastic or metal enclosure without a good ground connection is used,
then ESD diodes are needed to prevent damage to the PLT-22 transceiver. ESD
protection diodes include industry part types 1N4148 (thru-hole) and BAV99 (SMT).
Typical sources for BAV99 diodes include Motorola (BAV99LT1), National (BAV99),
and Diodes, Inc. (BAV99).

Neuron Chip Connections

The link between the Neuron Chip and the PLT-22 transceiver makes use of the
Neuron Chip's special-purpose mode interface. This interface requires that the CP
and ~RESET lines of the two devices be interconnected as shown in table 2.3.

Table 2.3 Neuron Chip and PLT-22 Transceiver Interconnections

®

packet is being received by the

The Neuron Chip and PLT-22 transceiver should be placed adjacent to one another
on the same printed circuit board. The length of the ~RESET and CP lines should be
kept to an absolute minimum and in no case should exceed 50mm (2"). In addition,

2-8 Using the PLT-22 Transceiver

Neuron Chip Pin PLT-22 Pin

CP0 7
CP1 6
CP2 5
CP3 Do not connect
CP4 4

~Reset 13

CLK1 10

the ground traces and V

trace between the PLT-22 transceiver and the Neuron

DD5

Chip should have impedances as low as possible.

The PLT-22 transceiver's CKOUT pin provides a clock suitable for driving the
Neuron Chip CLK1 at 1.25MHz, 2.5MHz, 5MHz, or 10MHz. The frequency of the
CKOUT pin (Neuron Chip CLK1 input) is selected by two pins, CKSEL0 and
CKSEL1/TXON, as shown in table 2.4. The Neuron Chip CLK2 pin is not connected.
The length of the CKOUT line should be kept to an absolute minimum and should in
no case exceed 50mm (2").

Table 2.4 PLT-22 Transceiver Output Clock Frequency Settings

CKSEL1/TXON CKSEL0 CKOUT FREQ. (MHz)

≥ 4.7k to GND (or open) GND 1.25
≥ 4.7k to GND (or open) VDD 2.5

4.7k to VDD V

5

DD

4.7k to VDD GND 10

The CKSEL1/TXON pin must never be connected directly to a supply rail. The
CKSEL1/TXON pin will draw large currents and potentially damage the
PLT-22 transceiver if it is connected directly to a supply rail. The CKSEL0

pin may be tied directly to V

or GND.

DD5

!

Note that when the PLT-22 transceiver is operated in its new dual
frequency mode (as described in Chapter 3, PLT-22 Transceiver
Programming) the Neuron Chip clock must be set to be 2.5MHz or higher.

The PLT-22 transceiver ~RESET pin is designed to connect directly to the Neuron

2,3,18

Chip ~RESET pin. The Neuron Chip Data Book

provides information on the

Neuron Chip’s external reset circuitry. Depending on the particular Neuron

Chip version used, a Low Voltage Indicator (LVI) circuit such as the
Motorola MC33064 or Dallas 1233 may be necessary to supply a reset signal
to both the Neuron Chip and the PLT-22 transceiver. All of the application

circuits shown in this documentation include an LVI chip. Consult your Neuron
Chip manufacturer for the latest reset circuit requirements. Whether an LVI chip or
a simpler discrete circuit is required, the ~RESET pin of the PLT-22 should always
be tied directly to the ~RESET pin of the Neuron Chip. To minimize the effect of
ESD discharges on the Neuron Chip ~RESET pin, use two external 56pF ceramic
capacitors, one tied between ~RESET and V

, the other between ~RESET and

DD5

GND. The capacitors should be placed as close as possible to the Neuron
Chip ~RESET pin. Note that the PLT-22 transceiver already incorporates two
56pF capacitors on the ~RESET line internal to the transceiver. These internal
capacitors should be taken into account when calculating the total allowable
capacitive load on the Neuron Chip ~RESET pin, as specified in the Neuron Chip

Data Book

2,3,18

.

LONWORKS PLT-22 Transceiver User’s Guide 2-9

Transmit Output Level

The TXLVL input pin on the PLT-22 transceiver determines the output voltage of the
transmit signal. When the TXLVL pin is left floating, the transceiver's open-circuit
output voltage is 3.5V p-p. When the TXLVL pin is grounded, the open-circuit
output voltage is increased by 6dB to 7Vp-p. The appropriate setting for TXLVL is
summarized in table 2.5.

TXLVL OUTPUT

grounded 7Vp-p Preferred mode of operation. Use for FCC,

open 3.5Vp-p Use for CENELEC EN50065-1 class 116

Table 2.5 TXLVL Setting

APPLICATION

VOLTAGE

Industry Canada, CENELEC class 134, Japan
MPT, and all dedicated wiring applications.

applications

TXON Output Signal

The PLT-22 transceiver provides an output signal suitable for controlling a PLA-21
Power Line Amplifier via the CKSEL1/TXON pin. The CKSEL1/TXON pin functions
as an input during the period in which the ~RESET pin of the PLT-22 transceiver is
held active (low). During the reset active period the logical states of the
CKSEL1/TXON and CKSEL0 pins are sampled and stored by the PLT-22
transceiver. The stored state is used to determine the frequency of CKOUT, as
described in table 2.4. After RESET becomes inactive (high) CKSEL1/TXON changes
to an output (CKSEL0 remains an input, but its state is ignored). The output, called
TXON, is a buffered version of the internal signal used to control the transceiver's
output amplifier. The TXON signal output is active high when the PLT-22
transceiver transmits packets.

The TXON signal is typically used to provide tri-state control of an external booster
amplifier, such as the PLA-21 Power Line Amplifier model 53001-01. For more
details see the PLA-21 Power Line Amplifier Specification and User's Guide.

2-10 Using the PLT-22 Transceiver

Optional power supply filter

(not required for linear

power supplies) See

chapter 5

See chapter 5

Power Supply

LINE

120 µF, 16VDC

Aluminum Electrolytic.

Close to PLT-22 VA pin.

See coupling circuits in

chapter 4

+VA

5

TANT,

Close to PLT-22

VDD pin

5 10 µF,10VDC

bypass

capacitors:

0.1 µF, 25VDC

6 places

VDD

1

2

RXIN

RXCOMP

EARTH

NEUTRAL

See chapter 4

Coupling Circuit

+5V

111215

5

VDD

CKSEL0

Optional Packet Detect and

Band-In-Use Indicators

470ž

470ž

* Refer to the Neuron 3150 Chip External

Memory Interface application note for

memory connection information.

GND for 7V p-p

transmit level;

Open for 3.5V p-p

4.7kž

14

16

BIU

PKD

TXOUT

CKSEL1

transmit level

21

TXLVL

3

A

+5V

+V

D0D1D2D3D4D5D6

13141518192021

O0O1O2O3O4O5O6

A0A1A2A3A4A5A6A7A8A9A10

98765

11

10

A0A1A2A3A4A5A6A7A8A9A10

D7

22

O7

4

292824

11217

26

NCNCNC

PROM

27C256

A11

A12

273303123

A11

A12

A13

2

+5V

PLT-22

~RESET

GND

CP4

CP2

+5V

+5V

32

16

NC

VDD

A13

A14

CE~

OE~

2

25

A14

A15

D7
D6
D5

D4

GND

D3
D2

+5V

D1

D0

VPP

+5V

33
34
35
36

37
38
39
40

41
42
43
44

open

45
46

A15

47
48

CP1

567

4

3

open

323130292827262524232221201918

CP4

CP3

CP2

CP1

D7

D6
D5

D4
D3
D2

VSS
VDD
VDD

D1
D0

VDD

R/~W

~E

A15

NC

NC

A14

A13

A12

495051525354555657585960616263

A11

A12

A13

A14

CKOUT

CP0

GND

8

10913

+5V

+5V

open

+5V

open

NC

CP0

VDD

VDD

VSS

CLK1

CLK2

VDD

VSS

Neuron 3150 Chip

A11

A10A9A8A7A6A5A4A3A2A1A0

GND

XIN18XOUT

17

19

10MHz

open

17

NC

VSS

IO10

~SERVICE

IO9
IO8

IO7

IO6
IO5
IO4
VSS
VSS

VDD
~RESET

IO3
IO2
IO1

IO0

NC

64

A0A1A2A3A4A5A6A7A8A9A10

Keep these lines short.

VA

20

+VA

16
15
14
13

12
11
10
9

8
7

+5V

6
5

4
3
2
1

MC33064D

1

56pF

+5V

56pF

Figure 2.2 Neuron 3150 Chip Application Schematic

Locate close to Neuron Chip

To User's Application Electronics

LONWORKS PLT-22 Transceiver User’s Guide 2-11

Optional power supply filter

(not required for linear

power supplies) See

Chapter 5

See Chapter 5

Power Supply

LINE

NEUTRAL

See Chapter 4

Coupling Circuit

1

2

RXIN

RXCOMP

EARTH

+5V

5

VDD

4.7kž

14

111215

BIU

CKSEL1

CKSEL0

Optional Packet Detect and

Band-In-Use Indicators

470ž

470ž

GND for 7V p-p

transmit level;

Open for 3.5V p-p

transmit level

PKD

16

TXOUT

21

TXLVL

CP2

567

open

CP3

D
D
V

+5V

CP1

CP1

VSS

CP0

CP0

CLK2

open

GND

8

+5V

17

VDD

CLK1

PLT-22

CKOUT

10913

CP2

VSS

~RESET

XIN18XOUT

10MHz

VA

19

20

VA

GND

17

Figure 2.3 Neuron 3120 Chip Application Schematic

3

2

+5V

MC33064D

1

56pF

+5V

56pF

Keep these lines short.

Locate close to Neuron Chip

A

V

+5V

CP4

GND

3

4

120 µF, 16VDC

Aluminum Electrolytic.

Close to PLT-22 VA

pin. See coupling

10 µF, 10VDC, TANT

VA

Close to PLT-22

VDD pin

+5V

5

circuits in chapter 4

5

VDD bypass

capacitors:

0.1 µF, 25VDC,

5 places

To User's
Application
Electronics

IO6

IO7

IO2

IO3

+5V

VDD

IO8

IO9

IO10

Neuron

3120 Chip

~SERVICE

IO0

IO1

VSS

Electronics
Application

To User's

CP4

VSS

D
D
V

VSS

10111213141516

+5V

+5V

323130292827262524232221201918

IO5

VSS

VDD

~RESET

VDD

IO4

123456789

+5V

2-12 Using the PLT-22 Transceiver

3

PLT-22 Transceiver Programming

Certain parameters of the PLT-22 transceiver are programmed by the
user. This chapter presents a list of these parameters and their
values, plus a description of how they are programmed via the

LonBuilder
Development Tool.

®

Developer’s Workbench and the NodeBuilder™

LONWORKS PLT-22 Transceiver User’s Guide 3-1

Dual Carrier Frequency Mode

Each PLT-22 transceiver incorporates a new dual carrier frequency capability which
allows it to communicate with other PLT-22-based nodes, even if noise is blocking its
primary communication frequency range. If impairments prevent communication in
this range, a PLT-22-based node can automatically switch to a secondary carrier
frequency to complete a transaction with other PLT-22-based nodes.

With dual carrier frequency mode enabled, the last two retries of acknowledged
service messages are sent using the secondary carrier frequency. Thus when
acknowledged service is used with three retries (four total tries), the first two tries
are sent using the 132kHz primary carrier frequency. If the last two tries are needed
to complete the transaction, they are sent (and acknowledged) using the 115kHz
secondary carrier frequency. A minimum of two retries must be used if the PLT-22
transceiver is to be able to use both carrier frequency choices. For optimum
reliability and efficiency, Echelon recommends the use of three retries when using
acknowledged service messaging with the PLT-22 transceiver.

When unacknowledged repeat message service is used, the PLT-22 transceiver
leverages the reliability of both carrier frequencies by alternating between them. In
this case an unacknowledged repeat message with three repeats results in the first
and third packets being sent using the 132kHz primary carrier frequency, while the
second and fourth packets are sent using the 115kHz secondary carrier frequency. A
minimum of one repeat must be used for the PLT-22 transceiver to use both carrier
frequency choices.

Every PLT-22 transmission at the 115kHz secondary carrier frequency is
accompanied by a simultaneous 132kHz “pilot” signal which older PLT-20 and PLT­21-based nodes can use to recognize that the channel is busy. This pilot signal
prevents PLT-20- or PLT-21-based nodes (which cannot detect the 115kHz secondary
carrier frequency) from transmitting at the same time that a PLT-22 is transmitting
on its 115kHz secondary carrier frequency.

The user can configure a PLT-22-based node to operate with the dual carrier
frequency mode either enabled or disabled. When a PLT-22-based node is operated
with dual carrier frequency mode enabled, it will operate as described above. When
a PLT-22-based node is operated with dual carrier mode disabled, it will only
transmit using its 132kHz primary carrier frequency. Note that the selection of dual
frequency mode on a PLT-22-based node only affects its transmission characteristics.
Each PLT-22 transceiver is always able to automatically detect and properly receive
packets at either frequency, regardless of whether or not dual frequency
transmission is enabled. Activation of dual carrier frequency mode is controlled by
the revision level of standard transceiver parameters, as described later in this
chapter.

3-2 PLT-22 Transceiver Programming

CENELEC Access Protocol

To allow multiple power line signaling devices from different manufacturers to
operate on a common AC mains circuit, the CENELEC standard EN 50065-1
specifies an access protocol for the C-band (125kHz to 140kHz). The frequency

132.5kHz is designated as the primary band-in-use frequency that indicates when a
transmission is in progress.

Every power line signaling device must both monitor the 132.5kHz band-in-use
frequency and be able to detect the presence of a signal of at least 80dBµVrms
anywhere in the range from 131.5kHz to 133.5kHz which has a duration greater
than or equal to 4 milliseconds. A power line signaling device is permitted to
transmit if the band-in-use detector shows the band to have been free for at least 85
milliseconds. Each device must randomly choose an interval for transmission, and at
least seven evenly distributed intervals must be available for selection. A group of
power line signaling devices is allowed to transmit continually for a period less than
or equal to one second, after which it must cease transmitting for at least 125
milliseconds.

The PLT-22 transceiver incorporates the CENELEC access protocol and the user can
enable or disable the CENELEC access protocol at the time of channel definition.
When enabled, the PLT-22 transceiver enforces the CENELEC access protocol while
still maintaining the benefits of the LonTalk protocol. When the CENELEC access
protocol is enabled, overall network throughput is reduced by 11%.

Power Management

The PLT-22 transceiver incorporates a power management feature that supports the
design of very low cost power supplies in low cost consumer applications such as
networked light dimmers, switches, and household appliances. This class of
consumer applications have low transmit duty cycle operation requirements. These
low cost power supplies take advantage of a number of PLT-22 features: the low
receive current requirements of the PLT-22 transceiver; the 9:1 difference between
the PLT-22 transceiver transmit and receive mode currents and the wide (+8.5VDC
to +16VDC) V

A low transmit duty cycle implies that the device transmits packets infrequently,
e.g., the product waits for a minimum of 10 packet times between transmitting each
packet - a 10% transmit duty cycle. A power supply design that takes advantage of
this duty cycle can store energy on a capacitor during the relatively long period
between transmissions, when the PLT-22 transceiver draws minimal current, and
then consume the stored energy to transmit a packet. This type of power supply,
referred to as an “energy storage power supply,” stores energy by charging an energy
storage capacitor to a relatively high voltage (e.g., 15V) while in receive mode. The
voltage on the capacitor then falls or "droops" toward a lower limit (e.g., 9.0V) while
transmitting. The energy storage capacitor is then slowly recharged to the higher
voltage during the relatively long time between transmissions. Traditionally, the
proper design of such a power supply required knowledge of the maximum transmit
duty cycle to be supported, and an implementation that accounted for all worst case

operating voltage of the PLT-22 transceiver.

A

LONWORKS PLT-22 Transceiver User’s Guide 3-3

operating conditions (temperature, line voltage, component variation and
transmitter loading).

The cost of such a power supply can be significantly reduced if, instead of designing
the supply for the maximum possible transmit duty cycle and for the worst case
environmental conditions, the supply can be designed for typical operating
conditions. However, designing for typical operating conditions implies that a
mechanism exists to "manage" the worst case operating conditions such that reliable
operation is assured. This management feature must also address products whose
operating conditions (especially transmit duty cycle) are not defined prior to use in a
network, but rather are controlled by application programs loaded after installation.

The PLT-22 power management feature implements the needed management
functionality by intelligently monitoring the energy storage power supply. Should
the node attempt to transmit too frequently, the power management feature
enforces a limit on the transmit duty cycle by preventing the Neuron Chip from
transmitting until the node's power supply recovers to the point that sufficient
energy is available to transmit a packet. Details of this feature and application
examples are provided in Chapter 5.

When power management is enabled, the PLT-22 transceiver requires a V

A

power supply voltage of 12.9V before it will attempt to transmit a packet.
Products with fixed V

power supplies lower than 12.9V should never be

A

programmed to enable the power management feature as they may never
be allowed to transmit. Likewise a node whose power supply relies on
power management to operate correctly should never

be programmed with

the power management feature disabled.

The user can enable or disable power management at the time of channel definition
by selecting a standard transceiver type with a "low" suffix. The only difference
between a set of standard transceiver parameters with the "low" suffix and the
corresponding set without the "low" suffix is that the power management feature is
enabled with the "low" set and disabled with the set without the suffix.

Note that some installation tools load a device's communication parameters as part
of the installation and replacement process and calculate those parameters based on
the channel (rather than the particular device). Such tools can not be used for
systems that contain a mixture of nodes with and without power management
enabled on the same channel.

Tools based on the L

ONWORKS Network Services (LNS) architecture, such as

LonMaker for Windows Integration Tool, correctly support all configurations of PLT­22 (and PLT-21) nodes with or without power management. For a tool not based on
LNS, contact your tool vendor to determine if it can support a mixture of power
management and non-power management nodes on the same channel.

Standard Transceiver Types

Four standard transceiver types are defined for the PLT-22 transceiver operating in
the 110 kHz – 140kHz range. These standard transceiver types specify
communications parameters for a PLT-22 (or PLT-20 or PLT-21) node. The

3-4 PLT-22 Transceiver Programming

communication parameters of the four standard types are identical except for the
state of the CENELEC protocol and power management features (enabled or
disabled) of the PLT-22 node. The revision level for each of these parameter sets
determines whether the dual carrier frequency feature of the PLT-22 transceiver is
enabled or disabled. When used with a STDXCVR.TYP file with a date prior to 1999,
the PLT-22 transceiver will only transmit packets using its 132kHz primary carrier
frequency. In this mode, all transmissions are compatible with prior generation
PLT-20 and PLT-21 transceivers.

The dual carrier frequency mode can be enabled by using updated standard
transceiver parameters. Standard transceiver parameters are used in the
LonBuilder and NodeBuilder development tools, and in the firmware of a number of
Echelon’s “connectivity” products as well (e.g., the Echelon RTR-10 router core). See
the next section for a discussion of how to update the LonBuilder and NodeBuilder
tools, and see the power line products section of Echelon’s web site
(www.echelon.com) to determine how to update other devices used in a PLT-22 power
line network.

With dual frequency mode activated, a PLT-22 transceiver begins each transaction
by sending backward compatible 132kHz packets. In this mode, the last two tries of
acknowledged service messages are sent using the 115kHz secondary carrier
frequency. For unacknowledged repeated messages, every other repeat is sent at the
secondary frequency. When the primary frequency range is not blocked by noise, a
PLT-22-based node can inter-communicate with any other PLT-20, PLT-21, and PLT­22 node. In addition, with the dual frequency mode activated, PLT-22-based nodes
can intercommunicate even if the primary frequency range is blocked by noise.

Table 3.1 lists the names of the four standard transceiver types and shows the
differences between them.

Table 3.1 Standard PLT-22 Transceiver Types

Standard Transceiver Type CENELEC Protocol Power Management

PL-20C Enabled Disabled

PL-20N Disabled Disabled

PL-20C-LOW Enabled Enabled

PL-20N-LOW Disabled Enabled

Table 3.2 shows which combinations of standard transceiver types and power supply
types are allowed.

LONWORKS PLT-22 Transceiver User’s Guide 3-5

Table 3.2 Allowed Power Supply Types Versus Standard Transceiver Types

Standard Transceiver
Type Selection

PL-20C OK Not allowed if the power supply design

PL-20N OK Not allowed if the power supply design

Fixed V
supply <12.9V

power

A

Energy Storage VA power supply
>12.9V

relies on power management for worst
case duty cycle and load conditions

relies on power management for worst
case duty cycle and load conditions

PL-20C-LOW Not allowed: node

may not transmit

PL-20N-LOW Not allowed: node

may not transmit

OK

OK

LonBuilder and NodeBuilder PLT-22 Transceiver Channel
Definitions

To use the PLT-22 transceiver in dual frequency mode with the LonBuilder or
NodeBuilder tools, you must have STDXCVR.TYP file with a date stamp of 1999 or
later. PLT-22-based nodes built from a system with a STDXCVR.TYP file earlier than
1999 will transmit using only a single carrier frequency, even if it is blocked by noise.
To take advantage of the PLT-22 transceiver's ability to automatically change
frequency if the primary frequency range is blocked by noise, verify that the year on
the date of your STDXCVR.TYP file is 1999 or later. This file is located in the
L

ONWORKS TYPES directory (c:\lonworks\types by default) for the NodeBuilder

software, and in the LonBuilder TYPES directory (c:\lb\types by default) for the
LonBuilder software. If the date on your STDXCVR.TYP file is older than 1999, you
can download an update from Echelon's web site at www.echelon.com/toolbox.

Once you have verified that you are using the correct version of the STDXCVR.TYP
file, specify PL-20N, PL-20C, PL-20N-LOW, or PL-20C-LOW as the standard
transceiver type in the NodeBuilder Device Template, as shown in figure 3.1, or the
LonBuilder Channel Create window. Select “Yes” for the “Enforce Standard Type”
field.

3-6 PLT-22 Transceiver Programming

Figure 3.1 NodeBuilder Device Template Window

Table 3.3 shows the channel definition parameters for the PLT-22 transceiver. If you
do not have access to an updated STDXCVR.TYP file, these channel definition
parameters may be entered in the Channel Modify screen and sub-screens to create a
standard PLT-22 transceiver definition which will activate the PLT-22 transceiver's
dual frequency mode.

Table 3.3 Channel Definition Parameters for the PLT-22

Transceiver

Parameter Value

Channel Modify Screen

Std Xcvr Type Custom
Comm Mode Special Purpose
Comm Rate 1.25Mbps
Number of Priorities 8
Min Clock Rate 2.5MHz
Avg Pkt Size 15 bytes
Osc Accuracy 200ppm
Osc Wakeup 0 µsec

LONWORKS PLT-22 Transceiver User’s Guide 3-7

Table 3.3 Channel Definition Parameters for the PLT-22

Transceiver (continued)

Comm Mode Specific Parameters
Channel Bit Rate 3987 bps
Alternate Bit Rate 3987 bps
Wakeup Pin Dir Output
Xcvr Controls Preamble? Yes
General Purpose Data (power management disabled)
CENELEC Access Protocol OFF
CENELEC Access Protocol ON
General Purpose Data (power management enabled)
CENELEC Access Protocol OFF
CENELEC Access Protocol ON

0E 01 00 10 00 00 00
4A 00 00 10 00 00 00

0E 01 00 12 00 00 00
4A 00 00 12 00 00 00

Allow Node Override?
PL-20N, PL20C PL-20N-LOW, PL-20C-LOW

Layer 1 Time Factors

YES

Rcv Start Delay 7.3 bits
Rcv End Delay 1.6 bits
Indeterm Time 10.1 bits
Min Interpacket 17.5 bits
Preamble Len 33.5 bits
Use Raw Data? No

The standard transceiver definitions in table 3.1 were chosen as the best balance between
flexibility in network design and network throughput. Flexibility is provided by the
selection of 8 priority slots on the channel and a minimum input clock of 2.5MHz (a Neuron
Chip input clock frequency as low as 2.5MHz may be chosen in order to reduce node power
consumption). These parameters support a packet rate of 10 packets/sec with 80%
throughput, 4% collisions, and 11 byte packets.

Note that when the PLT-22 transceiver is operated in its dual carrier mode, the minimum
Neuron Chip clock is 2.5MHz. When the PLT-22 transceiver is operated in its single carrier
frequency mode, the minimum Neuron Chip clock is 1.25MHz.

3-8 PLT-22 Transceiver Programming

!

4

Coupling Circuits

This chapter includes a technical discussion about the means by which
communication signals are coupled to power mains. Coupling circuit
designs, including schematics and electrical safety issues, are included.

LONWORKS PLT-22 Transceiver User’s Guide 4-1

Power Line Communications

The PLT-22 transceiver employs sophisticated digital signal processing techniques, a
transmit power amplifier with a very low output impedance, and a very wide (80dB)
dynamic range receiver to overcome the signal attenuation and noise inherent in
power mains communication. Maintaining the full communication capability of the
PLT-22 transceiver requires careful selection and implementation of the mains
coupling circuitry external to the PLT-22 transceiver. This section gives an overview
of the sources of signal attenuation as a basis for understanding choices in selecting
and implementing mains coupling circuits.

Attenuation is the difference between the signal level at the output of the power line
transmitter and the level of that same signal at the input of the intended receiver.
While attenuation is technically defined as the ratio of power levels, it is referred to
in this document as the ratio of the transmitted signal voltage (unloaded) to the
voltage of that same signal at the receiver input. A voltage ratio is more convenient
to measure since power measurements require knowledge of the circuit impedance
which, in the case of the power mains, varies with both location and time.

In power mains communications the attenuation of transmitted signals spans a wide
range and is most conveniently denoted in decibels (dB), where voltage attenuation is
defined in dB as 20log

signal was reduced by a factor of 10 by the time it arrived at the receiver, 40dB of
attenuation corresponds to a factor of 100, 60dB a factor of 1000, and so on. A PLT-22
transceiver is capable of reliably communicating on a low-noise line, such as a
dedicated twisted wire pair, when the transmit signal is attenuated by as much as
80dB (a factor of 10,000). Thus a signal transmitted at 7Vp-p (2.5Vrms) may be
received when reduced to less than 700µVp-p (250µVrms).

To better understand the sources of attenuation in a power mains network, it is
helpful to look at a simplified model of a power distribution network. This example
is based on an installation having one power distribution panel and two phases of
mains power. While many applications for power line communication employ more
phases, different topologies, voltages, and wire types, this example illustrates some
of the key issues affecting the successful application of the PLT-22 transceiver.

Figure 4.1 depicts the path that a power line communication signal might traverse,
starting from a wall socket and passing through the building's electrical wiring and
circuit breaker panel, across power phases, and ultimately to another wall socket.
Each socket in the power network may power a device that generates noise and loads
the transmitted signal. For clarity, neutral and earth wires have not been shown.

(

V

10

transmit/Vreceive

). Thus 20dB of attenuation means that the

4-2 Coupling Circuits

L2

L1

TX

RX

TXRX

Figure 4.1 Power Distribution Model

Attenuation is most easily understood in terms of a voltage-divider circuit formed by
the output impedance of the transmitter, the impedance of the various mains circuit
branches, and any loads present on the mains branch circuits. At the communication
frequencies of the PLT-22 transceiver (110kHz to 140kHz), the significant
impedances are due to the series inductance of the mains wiring itself, capacitive
loads between line and neutral, resistive loads between line and neutral, and the
coupling between L1 and L2 which occurs due to mutual inductance and parasitic
capacitance between phases. If these distributed impedances are lumped together
and treated as if a single frequency is being transmitted, the simple model shown in
figure 4.2 results.

LONWORKS PLT-22 Transceiver User’s Guide 4-3

Transmitter

Transmitter

Z

o

ZZ

Wiring

Phase-to-Phase

Z

Wiring

Receiver

Z

Load

Figure 4.2 Power Mains Attenuation Model

This model illustrates that minimizing the series impedances and maximizing the
line-to-return path impedances reduces the attenuation of the transmitted signal.

Coupling Techniques

Power Line Coupling Basics

Injecting a communication signal into a power mains circuit is normally
accomplished by capacitively coupling a transceiver's output to the power mains. In
addition to the coupling capacitor, an inductor or transformer is generally present.
The coupling capacitor and the inductor or transformer together act as a high-pass
filter when receiving the communications signal. The high-pass filter attenuates the
large AC mains signal (at either 50Hz or 60Hz), while passing the transceiver's
communication signal. Figure 4.3 below shows a basic mains coupling circuit. The
value of the capacitor is chosen to be large enough so that its impedance at the
communication frequencies is low, yet small enough that its impedance at the mains
power frequency (50Hz or 60Hz) is high. The impedance of the capacitor can be
considered as part of the transmitter's output impedance (Z

figure 4.2. Keeping the impedance of the coupling capacitor low minimizes the signal
injection loss caused by the voltage divider formed between the output impedance of
the amplifier and the mains loading (Z

Z

Load

Power Line Signal Return Path

Z

Load

).

Load

Receiver

Z

i

o

Transmitter

) shown in

The value of the inductor is chosen to have a relatively high impedance at the PLT­22 transceiver's communication frequencies. The inductor impedance can be
considered part of the receiver input impedance (Z

Keeping the inductor impedance high helps minimize any signal loss at the receiver
due to the voltage divider formed by the wiring impedance and the receiver input
impedance.

4-4 Coupling Circuits

i Receiver

) shown in figure 4.2.

PL Transmitter

Power Line
(AC Mains)

PL Receiver

Figure 4.3 Basic Mains Coupling Circuit

A key factor affecting the type of mains coupling circuit to be used is the wiring style
of the power distribution system to which the coupling circuit will be connected.
Wiring topologies vary from application to application, e.g., homes versus commercial
buildings, as well as from country to country. Even so, wiring styles can be divided
into two major categories: wiring systems where a separate earth conductor is
present and accessible (i.e., safety ground, which is not the same as a neutral wire
with an earth bond), and wiring systems where there is no earth conductor.

When earth is always present, a coupling method known as line-to-earth coupling is
preferred. In line-to-earth coupling the communications signal is coupled to the line
wire relative to earth, and earth is used as the communications signal return path.
This coupling technique is also referred to as earth-return coupling. Local restrictions
may apply to the use of line-to-earth coupling; see Ground Leakage Currents later in
this chapter.

A simple example of a line-to-earth coupling circuit is shown in figure 4.4.

LONWORKS PLT-22 Transceiver User’s Guide 4-5

PL Transmitter

Line

Earth

PL Receiver

Figure 4.4 Line-to-Earth Coupling Method

To understand the advantage of line-to-earth coupling, recall that a major component
of signal attenuation is due to the loads presented by devices that are connected to
the power mains between the line and neutral wires. These loads do not affect signal
attenuation when line-to-earth coupling is used. Field measurements have shown
consistent improvements in received signal-to-noise ratios of more than 15dB for
transceivers using line-to-earth coupling, relative to transceivers using non-earth­return coupling. For this reason, when a safety ground connection is known to be
available throughout the wiring system, a line-to-earth coupling scheme is preferred.

In applications where a safety ground connection may not exist, or line-to-earth
coupling is precluded by local regulations, the coupling circuit must be connected
between the line and neutral wires. This style of coupling is known as line-to-neutral
coupling and is shown in figure 4.5.

4-6 Coupling Circuits

PL Transmitter

Line

Neutral

PL Receiver

Figure 4.5 Line-to-Neutral Coupling Style

In the following section the simple circuits shown in figures 4.4 and 4.5 are expanded
to make them practical in real applications. The following discussion applies to both
line-to-neutral coupling and line-to-earth coupling, as the coupling circuit topology
for each is the same. However, in addition to the different mains connections, the
required component values differ for line-to-neutral coupling and line-to-earth
coupling. At the end of this chapter, recommended coupling circuit schematics and
component specifications are provided for both line-to-neutral coupling and line-to­earth coupling.

LONWORKS PLT-22 Transceiver User’s Guide 4-7

Power Line Coupling Details

The coupling circuits shown in figures 4.4 and 4.5 require the addition of a small
number of components to make them practical. Figure 4.6 shows the addition of an AC
coupling capacitor (C2) to prevent the inductor from shorting the transmit amplifier's
DC bias voltage.

PLT-22

Transmit
Amp

Receive Front End

Figure 4.6 Simplified Coupling Circuit with Blocking Capacitor

Given the attenuation model presented earlier in figure 4.2, one critical design
constraint is that the series combination of C1 and C2 must have a low impedance at
the PLT-22 transceiver's communication frequencies. The impedance of these
capacitors, along with the PLT-22 transceiver's transmit output impedance,
corresponds to “Zo Transmitter” in figure 4.2. Since the equivalent load impedance of

the power line may in some cases be as low as 1-2 Ohms, and since the output
impedance of the PLT-22 transceiver is less than 1 Ohm, the impedance of these
capacitors should be on the order of 1 Ohm so that they do not add significantly to “Zo

Transmitter”. While the values of C1 and C2 could be set high enough to meet this
goal, doing so would significantly increase the cost of the high-voltage capacitor C1.
Since C2 is connected only to low voltage, and thus is lower cost for a given value, its
value can be set higher relative to the value of the high-voltage capacitor C1. A simple,
cost-effective solution is obtained when an inexpensive inductor, L2, is added as shown
in figure 4.7 below. This inductor forms a series-resonant circuit with C1 and C2, and
its value can therefore be chosen to optimize coupling at the PLT-22 transceiver's
communication frequencies while minimizing the cost of C1 and C2.

C2

C1

L1

4-8 Coupling Circuits

PLT-22

Transmit Amp

C2

L2

Receive Front End

C1

L1

Figure 4.7 Simplified Coupling Circuit with Resonant Inductor

An important design constraint on L2 is that its DC resistance be kept very low since
it is in the transmit signal path and effectively part of the transmitter's output
impedance. Low-cost inductors with DC resistance on the order of 0.2 Ohms are
widely available.

Capacitors C1 and C2 should be of metalized polyester construction in order to
minimize equivalent series resistance and provide adequate surge immunity.

!

It is critical that no additional series impedance be added in the signal path
between the TXOUT pin of the PLT-22 transceiver and the power mains (or
in the return path from the power mains to the ground pins of the PLT-22)
unless verified to be significantly less than 1 Ohm near 130kHz. If, for

example, a ferrite bead with an impedance of 9 Ohms at 130kHz were added then the
signal injected into a 1 Ohm power line would be reduced by a factor of 10. Under
typical conditions the end product would still function, however, communication
margin and reliability over a full range of power line environments would be severely
compromised. For the same reason, the impedance of series circuit protection
elements must also be kept very low. Low current fuses (<2A), protection devices
that can be reset, and ferrite beads generally add unacceptable series impedance to
the signal path.

LONWORKS PLT-22 Transceiver User’s Guide 4-9

Figure 4.8 shows additions to the coupling circuit which are required to make it fully
functional. The first is a 1.0mH inductor, L3, connected to the PLT-22 transceiver receive
filtering circuitry. The DC resistance of L3 can be up to 50 Ohms. The second is a diode,
D1, connected from the transmitter to the amplifier supply voltage (V

) to protect the

A

inputs of the PLT-22 transceiver from large (>15V) transients. This diode works in
conjunction with a diode internal to the PLT-22 transceiver that connects from the
transmitter output to ground. Bypass capacitor C3 also has been added to emphasize the
fact that it is an integral part of the coupling circuit. One of the functions of this
capacitor is to protect the V

supply line from excessive overshoot when positive going

A

line surges discharge through diode D1. The last addition is an optional circuit that
improves performance in environments where large (>50V) impulses may be present from
devices such as SCR-controlled light dimmers. This circuit consists of an LCR series
network that acts as a notch filter whose center frequency is at the characteristic
“ringing” frequency of the coupling circuit. This optional circuit should be included on
nodes containing an SCR or triac switching device, and in nodes operating from a nominal
V

supply of less than 12V.

A

V

A

C3

+

PLT-22

D1

Transmit Amp

C2

L2

TXOUT

C1

Line

Optional
circuit

L1

Neutral or
Earth

Receive
Front
End

RXIN

RXCOMP

L3

Figure 4.8 Functional Line-to-Neutral or Line-to-Earth Coupling Circuit

In instances where large ambient fields may be present (such as from switched mode
power supply open frame magnetic elements), it is possible that one or more of the
PLT-22 coupling circuit inductors may pick up these stray fields and conduct them

4-10 Coupling Circuits

onto the power mains. Depending on the frequency and amplitude of these fields
they could result in failure to meet CENELEC conducted emission regulations.

If noise from parasitic coupling is suspected, it can be confirmed by inserting a 10cm
(4”) twisted wire pair in series with one of the inductors in question. If the conducted
noise spectrum varies by more than a few dB when this inductor is moved closer to,
and farther from, other components, then parasitic coupling may be the source of the
problem.

If stray coupling is a problem, regulations can usually be met by adjusting the
location or orientation of the radiating device relative to the coupling circuit
inductors. Alternately, shielded or toroidal inductors may be used to reduce coupling
as long as all electrical parameters specified in the example coupling circuit tables
given later in this chapter are met. If, however, a toroidal or shielded inductor is
used in place of L2, then the selected part must handle the maximum 1App output
current of the PLT-22 transceiver without approaching saturation. If L2 even
approaches saturation it can add harmonics of the PLT-22 transmit signal which
may result in failure to meet CENELEC emission regulations (in this instance, due
to inductor distortion instead of a stray pickup). For this reason, a shielded or
toroidal inductor used for L2 may need to have DC current rating two or three times
higher than listed in the example circuits given later in this chapter. The
recommended open frame axial inductor does not need this extra operating margin
due to the linearity provided by its magnetic path being partly in air.

Safety Issues

This guide is intended only as an introduction to some of the safety issues associated
with designing circuits using the PLT-22 transceiver. This document is not a primer
on electrical safety or electrical codes, and it is the responsibility of the user to
familiarize himself or herself with any applicable safety rules or regulations. A
review of all designs by competent safety consultants and the pertinent regulatory or
safety agencies is strongly recommended.

Safety Isolation Considerations

Many products include an isolation barrier in the form of an insulated enclosure
between a user and any hazardous conductors. A typical product of this type is a
light switch in which the PLT-22 transceiver and all of the associated electrical
components are contained inside the switch enclosure. The type of coupling circuit
that can be used in these applications is called a non-isolated coupling circuit. A
non-isolated coupling circuit generally requires lower cost components, making it
especially desirable for use in price-sensitive consumer products and wiring devices.
All of the coupling circuit examples that have been shown so far are of the non­isolated type.

Some products cannot practically incorporate an enclosed isolation barrier and an
alternate method of safety isolation must then be provided. For example, a circuit board
that uses a PLT-22 transceiver, a non-isolated line-to-neutral coupling circuit, and a
Neuron Chip whose I/O pins are user-accessible presents a potential electrical shock

LONWORKS PLT-22 Transceiver User’s Guide 4-11

hazard. Since the mains neutral lead is connected directly to the circuit board common,
the user could be exposed to a hazardous voltage at the I/O connector, especially if the
line and neutral connections are accidentally reversed. Additional circuitry is needed in
such a product to provide a safety isolation barrier between the user-accessible I/O
connector and the mains line and neutral conductors.

The most common solution is to provide isolation in the coupling circuit by modifying
the simple coupling circuit described earlier. This style of coupling circuit is referred
to as an isolated coupling circuit.

The preferred isolated coupling circuit uses transformer-isolation. Transformer­isolation requires substituting a safety agency-approved transformer having the
appropriate communication characteristics in place of L1 (see Appendix A).
Transformer-isolation can be used for both line-to-neutral and line-to-earth coupling.
Transformer-isolated coupling has the advantage that the resonant inductor L2 can
be incorporated into the isolation transformer by designing the leakage inductance of
the transformer to match the value of L2. A transformer-isolated coupling circuit is
shown in figure 4.9, where it can be seen that the transformer isolates the PLT-22
transceiver from the line conductor and the neutral or earth conductor.

V

A

C3

+

PLT-22

D1

Transmit Amp

Receive
Front
End

TXOUT

RXIN

RXCOMP

C2

L3

Optional
circuit

T1

C1

Line

Neutral or
Earth

Figure 4.9 Transformer-Isolated Coupling Circuit

An alternate method of providing safety isolation is to add optical isolation between
the Neuron Chip and the I/O connector, or between the Neuron Chip and the PLT-22
transceiver. If optical isolation is used between the Neuron Chip and the PLT-22
transceiver, then a maximum of 150ns propagation delay may be added to the CP

4-12 Coupling Circuits

interface lines in either direction and a separate crystal may be used for the Neuron
Chip clock.

Ground Leakage Currents

There are both safety and practical limits on the level of ground leakage currents that
are permitted in power line systems that use line-to-earth coupling. In the case of
products intended for use in commercial buildings and homes, many safety agency
standards set a maximum limit of 3.5mA of ground leakage current. This leakage limit
determines the maximum value of C1 (in figures 4.8 and 4.9) for line-to-earth coupling
circuits. In the application schematics that follow, the values for these capacitors have
been chosen to limit the ground leakage current to less than 3.5mA.

A practical limit on the use of line-to-earth coupling also exists. Many single circuit
ground fault interrupters (GFIs), also known as residual current devices (RCDs), can be
triggered with ground currents as low as 4mA. If each PLT-22 transceiver employing
line-to-earth coupling generates about 3mA of ground current, then only one such
transceiver can be installed on each GFI-protected circuit. For this reason line-to-earth
coupling may not be suitable for some applications with low-current GFIs, and line-to­neutral coupling should be used instead. Local regulations also may prohibit to the use
of earth as the return path for a signaling system.

Capacitor Charge Storage

The coupling capacitors depicted in the earlier figures can retain substantial charge
even after a PLT-22 transceiver-based device has been disconnected from the power
mains. This can be of significant concern in applications where a line cord could be
touched by a user after being disconnected from the power mains. To minimize
potential shock hazard, coupling circuits should include a large value bleeder resistor
to discharge the capacitors following disconnection from the mains. Even in
applications where the connection to the mains is permanently wired, it is good
practice to include the resistor to protect service personnel. The coupling circuit
schematics in this document include appropriate bleeder resistors.

Line Surge Protection

Coupling circuits that connect the PLT-22 transceiver to the power mains require the
addition of component(s) to provide protection of the PLT-22 transceiver from the
high-voltage surges that occur on all power distribution systems. Primarily lightning
induced, these surges can present voltages of up to 6kV at very high current levels
for brief periods to the coupling circuits inside buildings and homes. Even higher
voltages can be seen on mains wiring outside of buildings. The recommendations
that follow are based on testing performed on a particular PCB

LONWORKS PLT-22 Transceiver User’s Guide 4-13

layout. The efficacy of the surge protection implemented in each product containing
the PLT-22 transceiver must always be verified empirically, since factors such as
PCB layout and packaging can influence the results as much as the choice of
protection components.

The level of surge protection required for a given product often depends on the
installed location of the product to be protected. Devices connected to branch circuits
within a building or home are typically subject to the lowest level of surge stress.
Devices connected at, or close to, the power entry point of a building or home, e.g.,
electrical meters and main breaker panels, are subject to higher levels of surge
stress. Devices connected to outdoor wiring are subjected to the highest surge stress
of all.

Standard tests for surge immunity are defined in IEEE C62.41-1991
1000-4-5

16

. Both documents classify levels of surge stress by the type of surge wave-

17

and CEI/IEC

form (either Ring wave or Combo wave), surge voltage, and surge current. In
addition to describing standard test methods, both documents also suggest surge
immunity levels for the device environments described above.

Comparison of the two documents reveals that their recommended test procedures
are identical, while the suggested immunity levels called out in IEEE C62.41-1991
substantially exceed the suggested immunity levels of CEI/IEC 1000-4-5. The more
severe (and thus more conservative) immunity levels called out in IEEE C62.41-1991
were used in characterizing the recommended surge protection circuitry shown in the
PLT-22 transceiver coupling circuit examples that follow.

The line-to-neutral coupling circuits documented later in this chapter have been
demonstrated to meet the IEEE C62.41-1991 "high system exposure" levels with no
damage for branch circuit applications, power entry applications, and outdoor wiring
applications, up to the limits of the available test equipment.

Table 4.1 summarizes the surge immunity of the PLT-22 transceiver in conjunction
with the specified line-to-neutral coupling circuits.

4-14 Coupling Circuits

Table 4.1 Line-to-Neutral Coupling Circuit Surge Immunity Test Results

Product
Location

Branch Circuit low -2kV @70A

Power Entry low -2kV @170A

Outdoor Wiring

IEEE C62.41-1991
system exposure
level

med-4kV @130A

high-6kV @200A

med-4kV @330A

high-6kV @500A

Not specified

Ring Wave Test

(0.5µs-100kHz)

Surge level
verified not to
damage PLT-22

6kV @200A

6kV @500A

6kV @500A

IEEE C62.41- 1991
system exposure
level

Not specified

low -2kV @1,000A

med-4kV @2,000A

high-6kV @3,000A

low -6kV @3,000A

med-10kV @5,000A

high-20kV @10,000A

Combo Wave Test

(1.2/50µs-8/20µs)

Surge level
verified not to
damage PLT-22

6kV @500A

2kV @1,000A

6kV @3,000A

6kV @3,000A
(limited by test
equipment)

Surge protection with line-to-earth coupling is often constrained by the need to
maintain low leakage current. A varistor connected between line and earth adds
leakage current that may result in violation of applicable safety standards. This use
of a varistor for surge protection in line-to-earth coupling circuits is often prohibited.
Adequate surge immunity in branch circuit applications may be achieved without
varistors by the use of an X2-type capacitor instead of a non-safety rated metalized
polyester-type in the C1 location in line-to-earth coupling circuits. Surge immunity
may be further enhanced in power entry and outside wiring applications by the
addition of a gas tube surge arrester between line and earth.

If a gas tube surge arrestor is used between line and earth, the arrestor will have to
be loaded on the PCB after hi-pot testing. Hi-pot testing between line and earth is
usually performed at voltages above the break-down voltage of gas tube surge
arrestors, and the test will fail if a gas tube surge arrestor fires during testing.

The line-to-earth coupling circuits documented later in this chapter have been
demonstrated to meet the IEEE C62.41-1991 "medium system exposure" levels with
no damage for branch circuit applications, and the "high system exposure" levels
with no damage for power entry applications and for outdoor wiring applications (up
to the limits of the available test equipment).

LONWORKS PLT-22 Transceiver User’s Guide 4-15

Table 4.2 summarizes the surge immunity of the PLT-22 transceiver in conjunction
with the line-to-earth coupling circuits specified later in this chapter.

Table 4.2 Line-to-Earth Coupling Circuit Surge Immunity Test Results

Product
Location

Branch Circuit low -2kV @70A

Power Entry low -2kV @170A

Outdoor Wiring

Fuse Selection

Safety considerations may require a fuse in series with the mains connection. For an
end product to continue to function (without user intervention) it is necessary that the
selected fuse not open following a specified line surge. A minimum 6A time-lag (“slow
blow”) rating has been shown to be necessary to avoid unintentional fusing action at
“high system exposure” levels of IEEE C62.41-1991.

Ring Wave Test

(0.5µs-100kHz)

IEEE C62.41-1991
system exposure
level

med-4kV @130A

high-6kV @200A

med-4kV @330A

high-6kV @500A

Not specified

Surge level
verified not to
damage PLT-22

4kV @130A

6kV @500A

6kV @500A

Combo Wave Test

(1.2/50µs-8/20µs)

IEEE C62.41- 1991
system exposure
level

Not specified

low -2kV @1,000A

med-4kV @2,000A

high-6kV @3,000A

low -6kV @3,000A

med-10kV @5,000A

high-20kV @10,000A

Surge level
verified not to
damage PLT-22

3kV @250A

2kV @1,000A

6kV @3,000A

6kV @3,000A
(limited by test
equipment)

If a coupling circuit which incorporates varistor protection is selected, the varistor
manufacturer’s recommendations for maximum fuse current should be followed. The
vendor listed in the coupling circuits which follow suggests a maximum fuse rating of 6A
for use with 7mm (1200A) varistors and a maximum rating of 18A for use with 14mm
(4500A) varistors.

A 6A time-lag fuse is specified in all of the following coupling circuits since it satisfies all
of the above criteria, as well as the critical requirement that it add very little resistance
(<0.1 Ohms) to the transmit signal path. If a current rating greater than 6A is required
by the application then either larger varistor (>7mm) or gas discharge tube protection is
recommended.

Recommended Coupling Circuit Schematics

This section provides schematics and component information for coupling the PLT-22
transceiver to the power mains. Coupling circuits presented here are unchanged from
those recommended for use with the PLT-21 transceiver. The schematics are divided
into four classes based on coupling method and type of safety isolation. For each
schematic, component specifications and suggested suppliers/part numbers are provided.

4-16 Coupling Circuits

Vendor part number information is provided as a way to reduce component selection
times, since the suggested parts have already been verified to meet all required
specifications. Alternate component suppliers may be used provided that all
specifications listed for each component are met. While surge testing must be performed
for every new product design, using the suggested vendor part numbers listed in tables

4.1 and 4.2 has the additional advantage that the same vendor parts were verified by
Echelon.

For three phase coupling applications, the coupling circuit shown in Appendix A of the
L

ONWORKS Engineering Bulletin, Centralized Commercial Building Applications with

LONWORKS PLT-21 Power Line Transceiver (005-0056-01), is recommended.
Recommended coupling circuits for applications where two out-of-phase hot lines are
used (e.g., North American 240V appliances) and for 24VAC applications are listed in
LONWORKS Engineering Bulletin, Demand Side Management with LONWORKS Power
Line Transceivers (005-0070-01). Both of these bulletins are available on the Echelon
web site at www.echelon.com.

The PLT-22 transceiver also is fully compatible with all of the older coupling circuits
described in the following older documents: PLT-20 Power Line Transceiver User's Guide,
(version 3 or later), Demand Side Management Coupling Circuits Recommendations (14

February 1996), and Centralized Commercial Building Applications with L

ONWORKS PLT-

20 Power Line Transceiver.

LONWORKS PLT-22 Transceiver User’s Guide 4-17

Example 1: Line-to-Neutral (L-to-N), Non-Isolated Coupling Circuit

Figure 4.10 presents a schematic for a line-to-neutral, non-isolated mains coupling
circuit. Table 4.3 lists component values and recommended suppliers/part numbers
for coupling to the AC mains with a nominal line voltage in the range 100-240VAC.
For coupling to AC mains with a nominal line voltage in the range of 100-120VAC,
refer to table 4.4. This schematic may also be used for coupling to wiring other than
AC mains with AC or DC voltages of 250VRMS or less.

PLT-22

Transmit Amp

Receive
Front
End

V

A

TXOUT

RXIN

RXCOMP

D1

C3

L3

C1C2

L2

C4

See

L4

note
below

R2

L1

R1

Inductors L1 and L3 should be
spaced >1cm (0.4”) apart to avoid
undesirable parisitic coupling.

Line

F1

PROTECT

Neutral

Note: This optional circuit should be added to nodes with a nominal VA<12V or nodes that

4-18 Coupling Circuits

contain a triac or SCR load switching device.

Figure 4.10 L-to-N, Non-Isolated Coupling Circuit Schematic

Table 4.3 100-240VAC, L-to-N, Non-Isolated Coupling Circuit Component Values

Comp Value Specifications Vendor / Part Number

C1 0.068µF

±10%, ≥400VDC, metalized polyester

(1)

Matsushita Electric / ECQ-E4683KF

C2 0.82µF ±5%, ≥50VDC, metalized polyester Matsushita Electric / ECQ-V1H824JL
C3 ≥120µF ±20%, 16VDC, aluminum electrolytic,

Matsushita Electric / ECA-1CFQ121

≤ 0.3Ω ESR @100kHz
C4 0.068µF ±5%, ≥50VDC AVX / SR205C683JAA
D1 1A Reverse breakdown ≥50V, surge current ≥30A

1N4935

for 8.3mS, reverse recovery ≤200nS
F1 6A

250VAC, slow blow

(2)

L1, L3, L4 1.0mH ±10%, Imax≥30mA, RDC≤50Ω TAIYO YUDEN / LAL03NA102K

L2 18µH ±10%, Imax≥500mA, RDC≤0.3Ω TAIYO YUDEN / LAL05TB180K

R1 1MΩ

R2

82Ω-L4

RDC

(3)

PROTECT 300VAC(470VDC)

300VAC(470VDC)
240VAC

±5%, 1/4W, max working volt ≥360VDC

±5%, ≥1/16W

For indoor branch circuits use 7mm varistor

For power entry use 14mm varistor

For outdoor use AC gas discharge tube

(4)

(5)

Matsushita Electric / ERZ-V07D471
Matsushita Electric / ERZ-V14D471
CPClare / AC240L

Table 4.4 100-120VAC, L-to-N, Non-Isolated Coupling Circuit Component Values

Comp Value Specifications Vendor / Part Number

C1 0.10µF

±10%, ≥250VDC, metalized polyester

(1)

C2 0.82µF ±5%, ≥50VDC, metalized polyester Matsushita Electric / ECQ-V1H824JL
C3 ≥120µF ±20%, 16VDC, aluminum electrolytic,

≤ 0.3Ω ESR @100kHz
C4 0.10µF ±5%, ≥50VDC AVX / SR205C104JAA
D1 1A Reverse breakdown ≥50V, surge current ≥30A

for 8.3mS, reverse recovery ≤200nS
F1 6A

125VAC, slow blow

(2)

L1, L3, L4 1.0mH ±10%, Imax≥30mA, RDC≤50Ω TAIYO YUDEN / LAL03NA102K

L2 12µH ±10%, Imax ≥500mA, RDC≤0.3Ω TAIYO YUDEN / LAL05TB120K

R1 1MΩ

R2

82Ω-L4

RDC

(3)

PROTECT 150VAC(240VDC)

150VAC(240VDC)
120VAC

±5%, 1/4W, max working volt ≥200VDC

±5%, ≥1/16W

For indoor branch circuits use 7mm varistor

For power entry use 14mm varistor

For outdoor use AC gas discharge tube

(4)

(5)

(1)

In some applications an X2 safety rated capacitor may be required. Consult applicable safety standards.

(2)

In some applications a fuse may not be required. Consult applicable safety standards.

(3)

The value of R2 should be selected so that the series combination of the DC resistance of L4 and R1 is equal to 82Ω.

(4)

The working voltage rating of R1 may be achieved by using two 470kΩ resistors in series, each with a working

voltage rating of at least half of the value listed above.

(5)

Install the gas discharge tube on the line side of F1 (if a fuse is used).

Matsushita Electric / ECQ-E2104KF

Matsushita Electric / ECA-1CFQ121

1N4935

Matsushita Electric / ERZ-V07D241
Matsushita Electric / ERZ-V14D241
CPClare / AC120L

LONWORKS PLT-22 Transceiver User’s Guide 4-19

Example 2: Line-to-Neutral, Transformer-Isolated Coupling Circuit

Figure 4.11 presents a schematic for a line-to-neutral, transformer-isolated coupling
circuit. Table 4.5 lists component values and recommended suppliers/part numbers for
coupling to AC mains with a nominal line voltage in the range 100-240VAC. For
coupling to AC mains with a nominal line voltage in the range of 100-120VAC, refer to
table 4.6. This schematic may also be used for coupling to wiring other than AC mains
with AC or DC voltages of 250V

or less or for coupling to an unpowered wire pair.

RMS

V

A

C3

PLT-22

Transmit Amp

Receive
Front
End

TXOUT

RXIN

RXCOMP

D1

C2

L3

See
note
below

C1

T1

C4

L4

R2

R1

Line

F1

PROTECT

Neutral

Note: This optional circuit should be added to nodes with a nominal VA<12V or nodes that contain a

triac or SCR load switching device.

Figure 4.11 L-to-N, Transformer-Isolated Coupling Circuit Schematic

For long haul operations (≥ 300m) on lightly loaded lines communication distance
can be maximized by installing a termination circuit at each end of the cable.
Examples include unpowered twisted pair networks, low voltage networks, and
dedicated mains networks with minimal loading at the communication frequency of
the transceiver. A recommended termination circuit is shown in figure 4.12.

4-20 Coupling Circuits

100ž, 1/4W, ±5%

0.47µF, ±20%, non-polarized (voltage

rating must be suitable for application)

Figure 4.12 Termination Circuit

Table 4.5 100-240VAC, L-to-N, Isolated Coupling Circuit Component Values

Comp Value Specifications Vendor / Part Number

C1 0.10µF

±10%, ≥400VDC, metalized polyester

(1)

Matsushita Electric / ECQ-E4104KF

C2 0.82µF ±5%, ≥50VDC, metalized polyester Matsushita Electric / ECQ-V1H824JL
C3 ≥120µF ±20%, 16VDC, aluminum electrolytic,

Matsushita Electric / ECA-1CFQ121

≤ 0.3Ω ESR @100kHz
C4 0.10µF ±5%, ≥50VDC AVX / R205C104JAA
D1 1A Reverse breakdown ≥50V, surge current ≥30A

1N4935

for 8.3mS, reverse recovery ≤200nS
F1 6A

250VAC, slow blow

(2)

L3, L4 1.0mH ±10%, Imax≥30mA, RDC≤50Ω TAIYO YUDEN / LAL03NA102K

R1 1MΩ

R2

82Ω-L4

RDC

(3)

PROTECT 300VAC(470VDC)

300VAC(470VDC)
240VAC

(4)

±5%, 1/4W, max working volt ≥360VDC

±5%, ≥1/16W

For indoor branch circuits use 7mm varistor

For power entry use 14mm varistor

For outdoor use AC gas discharge tube

(5)

Matsushita Electric / ERZ-V07D471
Matsushita Electric / ERZ-V14D471
CPClare / AC240L

T1 See Appendix A

Table 4.6 100-120VAC, L-to-N, Isolated Coupling Circuit Component Values

Comp Value Specifications Vendor / Part Number

C1 0.10µF

±10%, ≥250VDC, metalized polyester

(1)

C2 0.82µF ±5%, ≥50VDC, metalized polyester Matsushita Electric / ECQ-V1H824JL
C3 ≥120µF ±20%, 16VDC, aluminum electrolytic,

≤ 0.3Ω ESR @100kHz
C4 0.10µF ±5%, ≥50VDC AVX / SR205C104JAA
D1 1A Reverse breakdown ≥50V, surge current ≥30A

for 8.3mS, reverse recovery ≤200nS
F1 6A

125VAC, slow blow

(2)

L3, L4 1.0mH ±10%, Imax≥30mA, RDC≤50Ω TAIYO YUDEN / LAL03NA102K

R1 1MΩ

R2

82Ω-L4

RDC

(3)

PROTECT 150VAC(240VDC)

150VAC(240VDC)
120VAC

±5%, 1/4W, max working volt ≥200VDC

±5%, ≥1/16W

For indoor branch circuits use 7mm varistor

For power entry use 14mm varistor

For outdoor use AC gas discharge tube

(4)

(5)

T1 See Appendix A

(1)

In some applications an X2 safety rated capacitor may be required. Consult applicable safety standards.

(2)

In some applications a fuse may not be required. Consult applicable safety standards.

(3)

The value of R2 should be selected so that the series combination of the DC resistance of L4 and R1 is equal to 82Ω.

(4)

The working voltage rating of R1 may be achieved by using two 470kΩ resistors in series, each with a working

voltage rating of at least half of the value listed above.

(5)

Install the gas discharge tube on the line side of F1 (if a fuse is used).

Matsushita Electric / ECQ-E2104KF

Matsushita Electric / ECA-1CFQ121

1N4935

Matsushita Electric / ERZ-V07D241
Matsushita Electric / ERZ-V14D241
CPClare / AC120L

LONWORKS PLT-22 Transceiver User’s Guide 4-21

Example 3: Line-to-Earth (L-to-E), Non-Isolated Coupling Circuit

Figure 4.13 shows a schematic for a line-to-earth, non-isolated mains coupling
circuit. Table 4.7 lists component values and recommended suppliers/part numbers
for coupling to AC mains with a nominal line voltage in the range 100-240VAC. For
coupling to AC mains with a nominal line voltage in the range of 100-120VAC, refer
to table 4.8. This schematic may also be used for coupling to wiring other than AC
mains with AC or DC voltages of 250V

RMS

or less.

PLT-22

Transmit Amp

Receive
Front
End

V

A

TXOUT

RXIN

RXCOMP

D1

C2

C3

L3

L2

See
note
below

C4

L4

R2

C1

L1

R1

Inductors L1 and L3 should be
spaced >1cm (0.4”) apart to avoid
undesirable parisitic coupling.

F1

Line

PROTECT

Earth

Note: This optional circuit should be added to nodes with a nominal VA<12V or nodes that contain a

4-22 Coupling Circuits

triac or SCR load switching device.

Figure 4.13 L-to-E, Non-Isolated Coupling Circuit Schematic

Table 4.7 100-240VAC, L-to-E, Non-Isolated Coupling Circuit Component Values

Comp Value Specifications Vendor / Part Number

C1 0.033µF

±10%, ≥250VAC, X2 type

(1)

Nissei Denki / Arcotronics
R40333K275XXXX

C2 0.82µF ±5%, ≥50VDC, metalized polyester Matsushita Electric / ECQ-V1H824JL
C3 ≥120µF ±20%, 16VDC, aluminum electrolytic,

Matsushita Electric / ECA-1CFQ121

≤ 0.3Ω ESR @100kHz
C4 0.033µF ±5%, ≥50VDC AVX / SR205C333JAA
D1 1A Reverse breakdown ≥50V, surge current ≥30A for

1N4935

8.3mS, reverse recovery ≤200nS

F1 6A

250VAC, slow blow

(2)

L1, L3, L4 1.0mH ±10%, Imax≥30mA, RDC≤50Ω TAIYO YUDEN / LAL03NA102K

L2 39µH ±10%, Imax≥500mA , RDC≤0.3Ω TAIYO YUDEN / LAL05TB390K

R1 1MΩ

R2

82Ω-L4

PROTECT none

240VAC
240VAC

RDC

±5%, 1/4W, max working volt ≥360VDC

(3)

±5%, ≥1/16W

For indoor branch circuits no component required

For power entry use AC gas discharge tube

For outdoor use AC gas discharge tube

(4)

(5)

n/a

(5)

CPClare / AC240L
CPClare / AC240L

Table 4.8 100-120VAC, L-to-E, Non-Isolated Coupling Circuit Component Values

Comp Value Specifications Vendor / Part Number

(2)

(1)

Nissei Denki / Arcotronics
R40683K275XXXX

Matsushita Electric / ECA-1CFQ121

1N4935

(4)

n/a

(5)

(5)

CPClare / AC120L
CPClare / AC120L

C1 0.068µF

±10%, ≥250VAC, X2 type

C2 0.82µF ±5%, ≥50VDC, metalized polyester Matsushita Electric / ECQ-V1H824JL
C3 ≥120µF ±20%, 16VDC, aluminum electrolytic,

≤ 0.3Ω ESR @100kHz
C4 0.068µF ±5%, ≥50VDC AVX / SR205C683JAA
D1 1A Reverse breakdown ≥50V, surge current ≥30A for

8.3mS, reverse recovery ≤200nS

F1 6A

125VAC, slow blow
L1, L3, L4 1.0mH ±10%, Imax≥30mA, RDC≤50Ω TAIYO YUDEN / LAL03NA102K

L2 18µH ±10%, Imax≥500mA, RDC≤0.3Ω TAIYO YUDEN / LAL05TB180K

R1 1MΩ

R2

82Ω-L4

RDC

PROTECT none

120VAC
120VAC

(1)

An X2-type capacitor is required for adequate surge immunity in branch circuit applications.

(2)

In some applications a fuse may not be required. Consult applicable safety standards.

(3)

The value of R2 should be selected so that the series combination the DC resistance of L4 and R2 is equal to 82Ω.

(4)

The working voltage rating of R1 may be achieved by using two 470kΩ resistors in series, each with a working voltage rating of at

least half of the value listed above. In addition, the peak power and peak voltage rating of R1 must be chosen to meet the high­pot testing requirements of the application.

(5) High-pot manufacturing tests must be performed proir to installation of this gas discharge tube. High-pot testing between line

and earth is usually performed at voltages above the gas tube arc-over voltage, and the test will fail if the gas tube arcs during
testing. In addition, a DC high-pot tester must be used to avoid excessive current flow through C1.

±5%, 1/4W, max working volt ≥200VDC

(3)

±5%, ≥1/16W

For indoor branch circuits no component required

For power entry use AC gas discharge tube

For outdoor use AC gas discharge tube

LONWORKS PLT-22 Transceiver User’s Guide 4-23

Example 4: Line-to-Earth, Transformer-Isolated Coupling Circuit

Figure 4.14 shows a schematic for a line-to-earth, transformer-isolated coupling
circuit. Table 4.9 lists component values and recommended suppliers/part numbers
for coupling to AC mains with a nominal line voltage in the range 100-240VAC. For
coupling to AC mains with a nominal line voltage in the range of 100-120VAC, refer
to table 4.10. This schematic may also be used for coupling to wiring other than AC
mains with AC or DC voltages of 250V

RMS

or less.

PLT-22

Transmit Amp

Receive
Front
End

V

A

TXOUT

RXIN

RXCOMP

D1

C2

C3

L3

L2

See
note
below

C1

T1

C4

L4

R2

F1

R1

Line

PROTECT

Earth

Note: This optional circuit should be added to nodes with a nominal VA<12V or nodes that contain a

Figure 4.14 L-to-E, Transformer-Isolated Coupling Circuit Schematic

4-24 Coupling Circuits

triac or SCR load switching device.

Table 4.9 100-240VAC, L-to-E, Transformer-Isolated Coupling Circuit Component Values

Comp Value Specifications Vendor / Part Number

C1 0.033µF

±10%, ≥250VAC, X2 type

(1)

Nissei Denki / Arcotronics
R40333K275XXXX

C2 0.82µF ±5%, ≥50VDC, metalized polyester Matsushita Electric / ECQ-V1H824JL
C3 ≥120µF ±20%, 16VDC, aluminum electrolytic,

Matsushita Electric / ECA-1CFQ121

≤ 0.3Ω ESR @100kHz
C4 0.033µF ±5%, ≥50VDC AVX / SR205C333JAA
D1 1A Reverse breakdown ≥50V, surge current ≥30A for

1N4935

8.3mS, reverse recovery ≤200nS

F1 6A

250VAC, slow blow

(2)

L2 27µH ±10%, Imax≥500mA, RDC≤0.3Ω TAIYO YUDEN / LAL05TB270K

L3, L4 1.0mH ±10%, Imax≥30mA, RDC≤50Ω TAIYO YUDEN / LAL03NA102K

R1 1MΩ

R2

82Ω-L4

RDC

±5%, 1/4W, max working volt ≥360VDC

(3)

±5%, ≥1/16W

(4)

T1 See Appendix A
PROTECT none

240VAC
240VAC

For indoor branch circuits no component required

(5)

(5)

For power entry use AC gas discharge tube

For outdoor use AC gas discharge tube

n/a
CPClare / AC240L
CPClare / AC240L

Table 4.10 100-120VAC, L-to-E, Transformer-Isolated Coupling Circuit Component Values

Comp Value Specifications Vendor / Part Number

(2)

(1)

Nissei Denki / Arcotronics
R40683K275XXXX

Matsushita Electric / ECA-1CFQ121

1N4935

(4)

n/a

(5)

(5)

CPClare / AC120L
CPClare / AC120L

C1 0.068µF

±10%, ≥250VAC, X2 type

C2 0.82µF ±5%, ≥50VDC, metalized polyester Matsushita Electric / ECQ-V1H824JL
C3 ≥120µF ±20%, 16VDC, aluminum electrolytic,

≤ 0.3Ω ESR @100kHz
C4 0.068µF ±5%, ≥50VDC AVX / SR205C683JAA
D1 1A Reverse breakdown ≥50V, surge current ≥30A for

8.3mS, reverse recovery ≤200nS

F1 6A

125VAC, slow blow
L2 5.6µH ±10%, Imax≥500mA, RDC≤0.4Ω TAIYO YUDEN / LAL04NA5R6K

L3, L4 1.0mH ±10%, Imax≥30mA, RDC≤50Ω TAIYO YUDEN / LAL03NA102K

R1 1MΩ

R2

82Ω-L4

RDC

±5%, 1/4W, max working volt ≥200VDC

(3)

±5%, ≥1/16W

T1 See Appendix A
PROTECT none

120VAC
120VAC

For indoor branch circuits no component required

For power entry use AC gas discharge tube

For outdoor use AC gas discharge tube

(1)

An X2-type capacitor is required for adequate surge immunity in branch circuit applications.

(2)

In some applications a fuse may not be required. Consult applicable safety standards.

(3)

The value of R2 should be selected so that the series combination the DC resistance of L4 and R2is equal to 82Ω.

(notes are continued on next page)

LONWORKS PLT-22 Transceiver User’s Guide 4-25

(4)

The working voltage rating of R1 may be achieved by using two 470kΩ resistors in series, each with a working

voltage rating of at least half of the value listed above. In addition, the peak power and peak voltage rating of R1
must be chosen to meet the high-pot testing requirements of the application.

(5) High-pot manufacturing tests must be performed proir to installation of this gas discharge tube. High-pot testing

between line and earth is usually performed at voltages above the gas tube arc-over voltage, and the test will fail if
the gas tube arcs during testing. In addition, a DC high-pot tester must be used to avoid excessive current flow
through C1.

4-26 Coupling Circuits

5

Power Supplies for the PLT-22

Transceiver

This chapter discusses options and requirements for the PLT-22
transceiver power supply. At the end of the chapter, requirements
for conducted emissions testing are discussed.

LONWORKS PLT-22 Transceiver's User Guide 5-1

Introduction

A

2

There are a number of power supply options available for use with the PLT-22
transceiver. These various options differ in key characteristics such as size and cost.

The following table is designed to aid in the selection of the optimal supply type.

Table 5.1 Power Supply Options

Power Supply
Type

Energy
Storage

pplication

Current

Neuron
Chip
Support

≤ 10mA 3120, E1,

E2

Safety­Isolated

No No 1 1 2

Universal
Input
(i.e., 88-

54VAC)

Capacitor
Input
Energy
Storage

≤ 20mA 3120, E1,

E2

Yes No 2 2 2

Linear
Traditional

Any All Yes No 3 ≥3 1 5-9

Linear
Pre-designed
Switcher
Off-the-shelf

approx.
100mA
Any All Yes Yes 6 ≥4 4 5-9

All Optional Optional 4 2 5

Switcher
Full Custom

Any All Optional Optional 5 ≥3 10

Switcher

Power Supply Design Considerations

In order to realize the full communications capability of the PLT-22 transceiver, it is
important to ensure that the power supply does not limit overall performance. Since
the power supply input is directly connected to the communications channel, it has
the potential both to attenuate the transmit signal and to couple noise into the input
of the receiver. Likewise, the power supply outputs, V

to degrade performance by coupling noise into the PLT-22 transceiver. The design or
selection of an appropriate power supply is critical in ensuring that neither power
supply loading nor power supply noise degrades communications performance.

Relative
Cost
(1 = low)

DD5

Relative
Size
(1 = low)

Relative
Design
Effort
(1 =low)

Page

5-3

and VA, have the potential

The following sections introduce some of the key design considerations in the
selection or design of a power supply. For additional detail, consult the sections
describing the specific power supply types.

Power Supply-Induced Attenuation

As discussed in Chapter 4, attenuation of a power line communication signal can be a
significant factor in overall system performance. A poorly chosen or poorly designed
power supply can greatly increase signal attenuation. In particular, the input stage
of a switching power supply can significantly attenuate both transmitted and
received power line communication
impedance at communication frequencies will require the addition of an inductor in

5-2 Power Supplies for the PLT-22 Transceiver

signals. Supplies which have a low input

series with the supply input. Optimal inductor selection will be covered in the
switching supply section of this chapter.

Power Supply Noise

Power supplies have the opportunity to introduce noise both at their inputs and
outputs. Noise conducted out of the input onto the AC line can degrade
communication performance as well as cause the device to violate emissions
regulations. Similarly, output noise can couple into the transceiver and degrade
communication performance.

Due to regulatory constraints, it is important to verify that the total noise conducted
onto the AC mains is adequately contained. Some supplies may require the addition
of an input filter as shown in the switching supply section of this chapter.

For information on conducted emissions test methodology, see chapter 6.

Energy Storage Power Supplies

In cost or size-sensitive devices, it may be desirable to use an energy storage
power supply. These supplies take advantage of the wide supply voltage range
and the disparity between the PLT-22 transceiver’s transmit and receive mode
current requirements, storing energy while the device is in receive mode and
expending it during signal transmission. By using an energy storage system, the
device can use a smaller, less expensive, power supply than an equivalent “full
power” device. In this way, a low-current supply may be used which only has to
supply the required receive mode current, plus an incremental current to
recharge a capacitor between transmissions.

In order for this energy-storage architecture to work, consideration must be
given to the capacitance value required to maintain an acceptably small supply
voltage drop during transmission. The capacitor value must be selected such
that proper node operation can be maintained during the transmission of a
maximum length packet. The definition of proper node operation includes
preserving transmit and receive functionality of the PLT-22 transceiver, as well
as maintaining V

supply regulation. The size of the capacitor can be

DD5

minimized by designing the supply to have the highest possible nominal voltage
while guaranteeing that VA will not exceed 16V, the maximum VA specification

of the PLT-22 transceiver. See Appendix C for details on how to balance network
messaging requirements with power supply designs.

For nodes set to transmit at 7Vp-p (TXLVL pin grounded), proper node operation is
then maintained when the node power supply meets both of the following conditions:

• VA ≥ 11.4V after the typical IA transmit load of 130mA has been active for

90.7ms

(1)

. This condition ensures adequate transmit amplifier headroom to drive
the full 7Vp-p signal onto the line under lightly loaded conditions. This condition
needs to be met only with nominal line input voltage and at room temperature.

• V

≥ 9.0V after the worst case IA transmit load of 250mA has been active for

A

90.7ms

(1)

. This condition ensures adequate headroom when the transmit

LONWORKS PLT-22 Transceiver's User Guide 5-3

amplifier is driving a low impedance line and its loaded output voltage is
somewhat less than 7Vp-p. For proper node operation this condition must be met
over the full range of worst-case component tolerances (including I

line voltage, and temperature.

drain), AC

DD5

Having chosen a storage capacitor to ensure adequate supply voltage after one packet,
the power management circuitry must then be enabled to prevent the erratic operation
of a node that transmits so frequently that its energy-storage capacitor cannot fully
recharge between transmissions. If the V

spaced packet transmissions, a linear regulator used to generate V

supply were to droop too far due to closely

A

would

DD5

eventually drop out of regulation. This would cause the node to experience a power-on
reset. Since it is difficult, if not impossible, for a developer to guarantee that a node
will not transmit too frequently, the PLT-22 transceiver’s power management circuitry
specifically covers this case.

The power management circuitry continuously monitors the VA supply voltage.
If the V

supply drops below the lower power management threshold (nominally

A

7.9V), the PLT-22 transceiver will prevent the Neuron Chip from transmitting
until the energy storage capacitor has sufficiently recharged to allow
transmission of a complete packet. The Neuron Chip and the PLT-22 transceiver
automatically work in concert to ensure the transmission of any waiting packets
once the capacitor has fully recharged. If a high packet transmission duty cycle
causes VA to drop too low, in turn causing the packet transmission to be aborted

prior to completion, the transceiver automatically signals the Neuron Chip to re­transmit the packet, independent of the LonTalk protocol service in use. Even
when unacknowledged service is employed, a packet that is interrupted by VA

droop will be re-transmitted once the power management system determines
that the supply has fully recharged.

The power management circuitry of the PLT-22 transceiver automatically
adjusts the amount of time that it inhibits transmission based on the node’s
actual recharge characteristics. This adaptive feature allows energy storage
nodes to typically transmit without constraint or intervention from the power
management circuitry. When a node powered by an energy storage supply has
worst case component tolerances and is exposed to low AC line voltage, the
PLT-22 transceiver’s power management circuitry actually measures the supply
recharge rate and calculates a suitable transmit hold-off time. The formula used
to make this calculation is three times the time required for the supply to charge
from its lower power management threshold (nominally 7.9V) to its upper power
management threshold (nominally 12.0V). Figure 5.1 illustrates examples of an
energy storage node operating under both typical and worst case conditions.

(1) The maximum packet length adequate for most applications is 34 bytes (this is

the maximum length for nodes which use default buffer sizes, input and output
network variables of 15 bytes or less, and non-explicit messaging). If the
application does not require both group addressing and 6 byte domains, then 32
bytes becomes the maximum. For the primary carrier frequency, a 32 byte
packet corresponds to a maximum transmission duration of 74.6ms.

Calculating the maximum transmission duration for a packet at the secondary
carrier frequency is somewhat more complicated due to the combination of error
correction and data compression used with that carrier frequency. If we
consider a case where message traffic satisfies three further common

5-4 Power Supplies for the PLT-22 Transceiver

conditions, then the maximum transmission duration can be calculated to be

90.7ms. This maximum duration is applicable for applications where: 1) there
are no priority packet transmissions from the energy storage node; 2) subnet
and node numbers are in the range 0 through 15; and 3) if a six byte domain is
used, it is assigned to be equal to a Neuron Chip ID number.

Transmission
Abort

Figure 5.1 Supply Voltage vs. Packet Transmission

Products incorporating an energy storage power supply must have the power
management feature of the PLT-22 transceiver enabled (by using the appropriate
standard transceiver type) to prevent signal transmission if the supply voltage
drops too low. The transceiver's power management system is software
selectable through the use of transceiver programming options as described in
Chapter 3.

Energy Storage Capacitor-Input Power Supplies

A particularly cost-effective example of an energy storage power supply is the
capacitor-input power supply. The most attractive feature of this supply is that
both V

approximately US$1.00-2.00.

and V

A

supplies can be built with just a few components for

DD5

Packet
Retransmit

Figure 5.2 illustrates the operation of a capacitor-input power supply. As shown in
the figure, a capacitor in series with the AC mains causes AC current to flow
through a zener diode, which acts as a shunt regulator. This regulator is selected to
limit the V

transceiver's VA supply. An energy storage capacitor is connected across the shunt
regulator to provide current capacity required for transmission. Note that unused

source current flows through the shunt regulator, maximizing the zener diode
temperature when the supply load is at a minimum. Since the regulation voltages
of zener diodes above 10V have strong positive temperature coefficients, a pair of
forward-biased silicon diodes, which have negative temperature coefficients, have
been added in series with a slightly lower-voltage zener diode. Note that this type
of capacitor-input power supply would inherently attenuate communication signals
if not for the addition of a series inductor, as shown in figure 5.2.

LONWORKS PLT-22 Transceiver's User Guide 5-5

supply voltage to ≤16V, the specified maximum value of the

A

Current
Source

Shunt

Regulator

Energy
Storage for
Transmission

Output
Voltage

VA (8.5V-16V)

V

DD5 (5V)

78L05

V

A

V

DD5

(8.5V - 16V)

(5V)

AC Line
Voltage

Input Capacitor

AC Line

Voltage

Raise Input Z

78L05

Partial

Temperature

Compensation

Figure 5.2 Capacitor-Input Power Supply Theory of Operation

Due to the low current available, the application of capacitor-input power
supplies is restricted to nodes which use 0.8µ or smaller geometry Neuron 3120
Chips and which require minimal I/O application current (e.g., latching relays,
SCR triggers, low-power LEDs). Figure 5.3 presents a schematic for a complete
node based on a Neuron 3120 Chip and powered by a capacitor-input power
supply. This node is designed to operate with an internal box air temperature
range of 0-70°C. The coupling circuit shown in this figure is different from those
shown in Chapter 4 to accommodate the unique requirements of this capacitor­input node.

The schematic contains a table which shows typical and worst-case transmit duty
cycles achievable with 120VAC and 230VAC lines for various capacitor values
and load options. Each of these options provides sufficient energy storage to
transmit one complete 90.7ms packet under worst-case conditions. Note that

the use of any of these capacitor-input power supply options requires
that the node's configuration data be programmed to enable power
management, as described in Chapter 3.

5-6 Power Supplies for the PLT-22 Transceiver

LONWORKS PLT-22 Transceiver's User Guide 5 - 7

Figure 5.3 Capacitor-Input Power Supply Schematic

Energy Storage Linear Supplies

For products requiring minimal application current and safety isolation, an
energy storage linear supply may be the smallest and most cost effective option.
Consider a node based on a Neuron 3120 Chip, operating at 2.5MHz and
consuming 1mA of application and I/O current. Using a linear power supply for
the V

requirements are presented in Table 5.2.

A traditional linear supply would require a transformer with an output current
rating of ≥300mA. By taking advantage of the PLT-22 transceiver’s power
management feature, an energy storage linear supply can be built with a 100mA
transformer.

supply and a linear regulator for the V

A

Table 5.2 Example Worst-Case Node Current Consumption

Transmit Receive

PLT-22 VA 250mA 6mA

PLT-22 V

18mA 23mA

DD5

Neuron 3120 Chip

(@2.5MHz)

Application & I/O

Current

78L05 Regulator

Current

Total 282mA 42mA

supply, the worst case current

DD5

8mA 8mA

1mA 1mA

5mA 4mA

Figure 5.4 shows an example of an energy storage linear supply. This example
supply meets the criteria listed in the energy storage section of this chapter.
With a transient load of 130mA for 90.7ms added to a constant 42mA receive
load, this supply does not droop below 11.4V. This supply also maintains ≥9.0V
after a 250mA load is added to the constant 42mA load for 90.7ms. Both of these
criteria hold true even with an AC line voltage which is 10% low and an output
capacitance value that is 20% low. In addition, this example supply supports
duty cycles of ≥50% under typical transmission conditions and ≥10% over worst
case line voltage and component tolerances.

12.6 VAC @100 mA

AC Line

4700 µF
16 V
±20%

78L05

Voltage

14 V, 5W
±5%
IN5351B

+

Figure 5.4 Energy Storage Linear Power Supply

Note that this supply is kept from exceeding the 16V maximum supply voltage
rating of the PLT-22 transceiver by the inclusion of zener diode over-voltage
protection. Without this diode, the combination of high AC line voltage and light

V

A

V

(5V)

DD5

5-8 Power Supplies for the PLT-22 Transceiver

output loading would result in output voltages >16V. In this application the
zener diode does not conduct unless the output load is light and the line voltage
is high.

In summary, an energy storage linear supply differs from a traditional linear
supply in the following ways:

1. Allows the use of a smaller transformer;

2. Requires more output capacitance for energy storage;

3. May require over-voltage zener diode protection;

4. Requires that the node be programmed to enable power management, as
described in chapter 3;

5. Under typical conditions, exhibits transmit duty cycles which are not limited.
Over the full range of line voltage and component tolerance, the PLT-22
transceiver’s power management may act to regulate a particular node’s
transmit duty cycle (to ≥10% in the above example).

Traditional Linear Power Supplies

This option is usually suitable if the physical size of the power supply is not
constrained in the application, since linear supplies tend to be physically larger
than switching power supplies. Linear power supplies do not load the power line
in the range of the PLT-22 transceiver's communication frequencies, nor do they
generate significant noise. For these reasons, a linear power supply may be used
without concern that communication performance will be adversely affected.

Switching Power Supplies

While generally smaller than linear power supplies, switching power supplies
can be a significant source of noise and power line signal attenuation. As a
result the required design effort is significantly greater than that required for
linear or capacitor-input power supplies.

Several design options are available for use if a switching power supply is required
due to size or application current constraints. These options include a pre­designed switcher, an off-the-shelf switcher, and a custom-designed switcher. They
are described following the discussion of switching supply design issues.

Power Supply-Induced Attenuation

The input stage of a switching power supply typically contains an EMC filter
that includes one or more capacitors connected directly from line to neutral and,
in many cases, additional capacitors from line and neutral to ground. When the
AC line terminals of the switching power supply are connected to the AC mains
(in parallel with the coupling circuit), additional signal attenuation occurs. This
loss can be avoided by inserting a series inductor between the power supply input
and the power line communication channel as shown in figure 5.5.

LONWORKS PLT-22 Transceiver's User Guide 5-9

Line

Switching Power

Supply

Neuron

Chip

PLT-22

Transceiver

Coupling

Circuit

Neutral

Earth

Figure 5.5 Reducing Attenuation Caused by a Switching Power Supply

Including this inductor is desirable because the increase in attenuation for a given
load is much worse when the load, in this case the switching power supply, is
connected directly to the transceiver. In contrast, the loading caused by a switching
supply that is separated from the receiver is reduced by the series inductance of
power line wiring.

The loading effect of a switching power supply almost always dictates the addition of
the inductor for L-to-N coupling circuits. The inductor may or may not be required
for L-to-E coupling circuits depending on the EMC filter topology of the switching
power supply. In either case, the value of the inductor should be chosen such that
the power supply does not impose a low impedance onto the power line in the
communication frequency range of 110kHz-140kHz. The appropriate value of
inductance is a trade-off between required impedance, which is a function of system
topology, and node cost. The selected inductor must have a current rating which is
greater than the peak current drawn by the power supply in order to avoid
impedance reduction due to inductor saturation. Higher impedances require larger
inductance values which are more expensive for a given power supply input current.

For most AC mains distribution systems, where communication frequency
impedances are typically in the range of 1 to 20 Ohms, a power supply input
impedance of 100 Ohms is sufficient to avoid added signal attenuation.

An example of a system that would benefit from an input impedance >100Ω would be
one in which 100 or more PLT-22 transceiver-based nodes were connected to a 1000m
powered, twisted pair cable. In this case the input impedance of the power supply
could limit either the maximum transmission distance and/or the maximum number
of transceivers that could be connected to the cable. To maximize communication
distance on dedicated twisted pair wiring where the system impedance is
approximately 100 Ohms, a minimum power supply input impedance of 500 Ohms is
recommended. For extreme cases with >100 nodes on dedicated lines longer than
1000m (3279 feet), a power supply input impedance of 2000 Ohms may be needed to
maximize communication distance. Table 5.3 shows the appropriate inductor value
by application.

5-10 Power Supplies for the PLT-22 Transceiver

Table 5.3 Inductor Value vs. Application

W

Application Network Impedance

@130kHz

Single building AC mains 1-20 Ohms ≥100 Ohms ≥120µH

Dedicated cable

≤100 nodes

≤100m

Dedicated cable

>100 nodes

>100m

50-100 Ohms ≥500 Ohms ≥680µH

50-100 Ohms ≥2000 Ohms ≥2.4mH

Inductor Impedance

@130kHz

Inductor Value

There is one further constraint on the value of the inductor. When the inductor is combined
with the input capacitance of the switching supply, the LC resonant frequency should be at
least one octave away from the communication frequency range (110 kHz-140kHz). The
unintentional series resonance between the inductor's reactance and the power supply's
capacitive reactance can produce a low impedance at communication frequencies if this
frequency range is not avoided.

One way to reduce the size and cost of an inductor used to raise a power supply's input
impedance is to purposefully parallel resonate it at the communication frequency with a
capacitor, as shown in figure 5.6. If this option is chosen, resistive damping must be
included so that impulsive power line noise does not excite excessive filter ringing, which
could degrade the reception of weak signals. The 330 Ohm parallel, and 3.3 Ohm series,
resistor values have been selected to optimize receive impedance and impulsive noise
damping. Note that even though only a 100µH inductor is shown in figure 5.6, a series
impedance of ≥200 Ohms from 125kHz to 140kHz is maintained due to the parallel resonant
effect. Also, note that the inductor must be rated for the peak AC current drawn by the
power supply; the 3.3 Ohm resistor should have a power rating consistent with the AC
current drawn by the power supply, and its voltage drop should be verified as acceptable.

330ž ±5% 1/4

Power

Mains

Switching

Power

0.015µF ±10%

100µH ±10%

3.3ž ±5%, 1/2W,
wire wound or carbon
composition

Supply

Neuron

Chip

PLT-22
Txcvr

Coupling

Circuit

Figure 5.6 Reducing Attenuation Caused by a Switching Power Supply with a

Resonant Circuit

LONWORKS PLT-22 Transceiver's User Guide 5-11

Noise at the Power Supply Input

In order to achieve maximum communication performance and to comply with
the conducted emissions specifications of CENELEC EN 50065-1 and FCC Part
15, the switching power supply input must not conduct excessive noise onto the
power mains. A switching power supply contains an oscillator that operates at a
frequency between 10kHz and several MHz. Depending on the power supply
design, significant energy at the switching frequency fundamental and/or its
harmonics may appear at the input (line side) of the power supply. If the
amplitude of the signal is large enough in sensitive frequency ranges, the
performance of the PLT-22 transceiver may be degraded.

While the PLT-22 transceiver is designed to operate reliably with a combination
of attenuation and significant switching supply noise, noise from the switching
power supply closest to the receiver will have the most deleterious effect on
communication performance. Noise from more distant sources will be attenuated
before reaching a receiver, reducing its effect on reception.

Switching Power Supply Frequency Selection

Selection of an appropriate operating frequency for a switching power supply will
minimize the effect of switching noise on the PLT-22 transceiver's
communication performance. By choosing an operating frequency such that the
fundamental and harmonics of that switching supply avoid the transceiver's
communication frequencies, the amount and cost of additional circuitry to filter
interference from the switching supply can be minimized. Table 5.4 below lists
the optimal switching frequency ranges. The switching supply should be
designed such that the fundamental switching frequency falls within the stated
ranges under all line, load, environmental, and production conditions.

Table 5.4 Optimal Switching Power Supply Fundamental Operating Frequencies

Optimal Frequency Ranges

80kHz-110kHz

>155kHz

Switching Power Supply Input Noise Masks

The noise "masks" presented below show the maximum noise allowable at the
input of a switching power supply such that optimum performance of the PLT-22
transceiver is achieved and the appropriate conducted emissions specification is
met. Figure 5.7 defines the noise mask for CENELEC EN 50065-1 conducted
emissions compliance. Figure 5.8 defines the noise mask for FCC-conducted
emissions compliance. The limits assume that the PLT-22 transceiver is used in
conjunction with one of the recommended coupling circuits shown in Chapter 4.

Measurements of a particular power supply should be made by connecting the
supply to the artificial mains network as specified in subclause 8.2.1 of CISPR
Publication 16, second edition. Measurements should be made over the full
range of anticipated loads on the supply since many switching supplies vary their
switching frequency with load. Two different limits are shown for the CENELEC

5-12 Power Supplies for the PLT-22 Transceiver

EN 50065-1 measurements. One limit is measured using a quasi-peak detector,
the other using an average detector. Note that those limits are the same as
required for any other CENELEC compliant product, except in the
communication range of 110kHz to 140kHz where lower noise levels are
specified.

For FCC applications, the limit of figure 5.8 corresponds to FCC Class B limits
for frequencies above 450kHz. Below 450kHz, the limits are set such that the
full communication performance of the PLT-22 transceiver is maintained. Two
lines are indicated. The solid "single carrier" line shows the noise limits required
to maintain full performance if the transceiver is used only in its single carrier
frequency mode. If the PLT-22 transceiver is going to be used in its dual carrier
frequency mode, then it is recommended that the power supply noise fall below
the dashed "dual carrier" line. Meeting this criteria ensures that the full
performance of both operating frequencies is available to overcome unexpected
power line noise in either of the two frequency ranges. A quasi-peak detector
should be used when verifying power supply noise against the limit lines of
figure 5.8.

For both CENELEC and FCC measurements, the measurement bandwidths are
200Hz for measurements below 150kHz, and 9kHz for measurements above
150kHz, as described in CISPR 16.

LONWORKS PLT-22 Transceiver's User Guide 5-13

110

100

90

80

70

60

50

40

30

20

1.0E+03 1.0E+04 1.0E+05 1.0E+06 1.0E+07 1.0E+08

Frequency (Hz)

Quasi-peak detector

Average detector

Figure 5.7 Switching Power Supply Input Noise Limits for CENELEC EN 50065-1

Compliance

110

100

90

80

70

60

50

40

30

20

1.0E+03 1.0E+04 1.0E+05 1.0E+06 1.0E+07 1.0E+08

Single carrier frequency mode

Dual carrier frequency mode

Frequency (Hz)

Figure 5.8 Switching Power Supply Input Noise Limits for FCC Compliance

5-14 Power Supplies for the PLT-22 Transceiver

Table 5.5 lists the endpoints of the straight lines shown in figure 5.7, and table

5.6 lists those shown in figure 5.8.

Table 5.5 Switching Power Supply Input Noise Limits for CENELEC EN 50065-1

Compliance

Frequency(kHz) Noise Level (dBuV):

Quasi-Peak Detector

Noise Level (dBuV):Average Detector

9 89 N/A

110 68 N/A

110+ 30 N/A

140 30 N/A

140+ 66 56

500 56 46

500+ 56 46

5000 56 46

5000+ 60 50

30000 60 50

Table 5.6 Switching Power Supply Input Noise Limits for FCC Compliance

Frequency(kHz) Single Carrier Frequency

Noise Level (dBuV):
Quasi-Peak Detector

Dual Carrier Frequency

Noise Level (dBuV):
Quasi-Peak Detector

9 100 89

40 100 76

40+ 80 76

50 80 75
50+ 80 75
110 80 68

110+ 80 30

125 80 30

125+ 30 30

140 30 30

140+ 70 60

450 70 60

450+ 48 48

30000 48 48

A power supply that does not meet the appropriate noise mask for the
power supply input may require a filter between the local switching
power supply and the power mains. A filter example which both attenuates

switching supply noise and provides >200 Ohm input impedance is shown in
figure 5.9. Note that both inductors must be rated for the peak AC current
drawn by the power supply; the 3.3 Ohm resistor should have a power rating
consistent with the AC current drawn by the power supply, and its voltage drop
should be verified as acceptable.

LONWORKS PLT-22 Transceiver's User Guide 5-15

!

330ž ±5% 1/4

W

wire wound or carbon

Power

Mains

Switching

Power

Supply

Neuron

Chip

100µH ±20%

0.015µF ±10%

100µH ±10%

3.3ž ±5%, 1/2W,

composition

0.47µF ±20%
X2 Type

250VAC

PLT-22
Txcvr

Coupling

Circuit

Figure 5.9 Optional Switching Power Supply LC Network

This filter has the attenuation characteristics shown in figure 5.10, when
connected to a 50Ω mains network. If the supply noise drops by less than the
values shown in figure 5.10 it is likely due to parasitic coupling between the two
inductors. If this occurs, filtering close to the level shown in figure 5.10 can
usually be accomplished by adjusting the relative location and orientation of the
inductors (orthogonal orientation typically reduces inductor coupling). Alternately,
shielded or toroidal inductors may be used to reduce coupling.

Communication

frequencies
(110 - 140kHz)

Attenuation (dB)

Frequency (Hz)

Figure 5.10 Filter Frequency Response

5-16 Power Supplies for the PLT-22 Transceiver

In some instances it is possible that noise radiated from either the power supply
or the supply filter may couple into the inductors of the transceiver's coupling
circuit. The coupling circuit may then couple this noise onto the power mains.
This problem can be diagnosed by disconnecting the transceiver's coupling circuit
and then analyzing the conducted line noise.

If noise from parasitic coupling is suspected, it can be confirmed by inserting a
10cm (4") twisted wire pair in series with one of the inductors in question. If the
conducted noise spectrum varies by more than a few dB when this inductor is
moved closer to, and farther from, other components, then parasitic coupling may
be the source of the problem.

There is a second, although less likely, potential cause for reduced filter
effectiveness. It is possible for the inductive reactance of the filter components to
be canceled by capacitive reactance from the input of the power supply. This
problem is generally seen as narrow band noise which appears to pass through
the filter unattenuated. This problem can be remedied by either damping the
unintended resonance, or by adjusting the values of the filter inductor and
capacitor to move the resonance to a non-interfering frequency. Damping may be
accomplished by adding resistance in the range of 200 Ohms to 5k Ohms in
parallel with the filter inductor closest to the power supply.

Switching Power Supply Output Noise Masks

The PLT-22 transceiver requires +5VDC (V

) and +8.5VDC to +16VDC (VA)

DD5

supply voltages. The amplitude of the noise and ripple on these power supply
outputs must be controlled in order to comply with CENELEC EN 50065-1 or
FCC-conducted emission limits, as well as to achieve maximum communication
performance. Noise "masks" are provided in figures 5.11 through 5.14. Figures

5.11 and 5.12 show the recommended noise (ripple) limits on the V

supply for

DD5

CENELEC EN 50065-1 and FCC compliance, respectively. Figures 5.13 and 5.14
show the recommended noise (ripple) limits on the V

supply for CENELEC EN

A

50065-1 and FCC compliance, respectively.

For each graph, two limit lines are indicated. The solid "single carrier" line shows
the noise limits required to maintain full performance if the transceiver is used
only in its single carrier frequency mode. If the PLT-22 transceiver is going to be
used in its dual carrier frequency mode, then it is recommended that the power
supply noise fall below the dashed "dual carrier" line. Meeting this criteria
ensures that full performance of both operating frequencies is available to
overcome unexpected power line noise in either of the two frequency ranges.

Measurements should be made over the full range of anticipated loads on the
supply, since many switching supplies vary their switching frequency with load.
For both CENELEC EN 50065-1 and FCC measurements, a quasi-peak detector
should be used. The measurement bandwidths are 200Hz for measurements
below 150kHz, and 9kHz for measurements above 150kHz.

Figure 5.15 shows a probe that can be used to measure the noise on the power
supplies. The twisted wires must be connected directly to the PLT-22 power and
ground pins, and the coaxial cable must be connected to the 50Ω measuring
equipment. Note that the 1/10 gain of the probe must be taken into account.

LONWORKS PLT-22 Transceiver's User Guide 5-17

110

100

90

80

70

60

50

40

1.0E+04 1.0E+05 1.0E+06

Single carrier frequency mode

Dual carrier frequency mode

Frequency (Hz)

Figure 5.11 V

Power Supply Noise Limits vs. Frequency for CENELEC

DD5

EN 50065-1 Compliance

110

100

90

80

70

60

50

40

1.0E+04 1.0E+05 1.0E+06

Single carrier frequency mode

Dual carrier frequency mode

Frequency (Hz)

Figure 5.12 V

Power Supply Noise Limits vs. Frequency for FCC Compliance

DD5

5-18 Power Supplies for the PLT-22 Transceiver

Table 5.7 and 5.8 lists the levels shown on the previous graphs in figures 5.11
and 5.12, respectively.

Table 5.7 V

Table 5.8 V

Table 5.9 and 5.10 list the levels shown on the graphs following in figures 5.13
and 5.14, respectively.

Power Supply Noise Limits vs. Frequency for CENELEC EN 50065-1 Compliance

DD5

Frequency(kHz) Single Carrier Frequency

Noise Level (dBuV)

10-20 100 75

20-37 90 75

37-110 75 75
110-125 75 45
125-140 50 45
140-250 65 65
250-350 70 65

350-1000 70 70

Power Supply Noise Limits vs. Frequency for FCC Compliance

DD5

Frequency(kHz) Single Carrier Frequency

Noise Level (dBuV)

10-37 100 75

37-50 80 75

50-110 90 75
110-125 90 45
125-140 50 45
140-325 80 75

325-1000 80 65

Dual Carrier Frequency

Noise Level (dBuV)

Dual Carrier Frequency

Noise Level (dBuV)

Table 5.9 V

Frequency(kHz) Single Carrier Frequency

Table 5.10 V

Frequency(kHz) Single Carrier Frequency

Power Supply Noise Limits vs. Frequency for CENELEC EN 50065-1 Compliance

A

Dual Carrier Frequency

Noise Level (dBuV)

10-37 100 65

37-50 80 65

50-110 90 65
110-125 90 40
125-140 40 40
140-325 70 70

325-1000 70 65

Power Supply Noise Limits vs. Frequency for FCC Compliance

A

Noise Level (dBuV)

10-37 100 65

37-50 80 65

50-110 90 65
110-125 90 40
125-140 40 40
140-325 70 70

325-1000 70 65

Noise Level (dBuV)

Dual Carrier Frequency

Noise Level (dBuV)

LONWORKS PLT-22 Transceiver's User Guide 5-19

110

100

90

80

70

60

50

40

30

1.0E+04 1.0E+05 1.0E+06

Single carrier frequency mode

Dual carrier frequency mode

Frequency (Hz)

Figure 5.13 V

Power Supply Noise Limits vs. Frequency for CENELEC

A

EN 50065-1 Compliance

110

100

90

80

70

60

50

40

30

1.0E+04 1.0E+05 1.0E+06

Single carrier frequency mode

Dual carrier frequency mode

Frequency (Hz)

Figure 5.14 V

Power Supply Noise Limits vs. Frequency for FCC Compliance

A

5-20 Power Supplies for the PLT-22 Transceiver

1 µF

Options

To 50ž
measuring
equipment

The following switching power supply options are available: pre-designed, off­the-shelf, and custom.

50ž coax

Figure 5.15 10x Power Supply Noise Probe

450ž

To PLT-22 SIP

Power Supply

50 cm

max

Pre-designed Switching Supplies

This option is highly recommended if a small, low-cost power supply is desired and
significant application current is required. Power Integrations has developed a
power supply based on their TOP210 chip to specifically meet all of the design
requirements for PLT-22 based nodes. This TOP210 design can supply a total of
400 mA at 12V and thus can support the PLT-22 transceiver operating in 7Vp-p
mode, a Neuron Chip plus about 100mA of application electronics. Detailed design
information, including schematic and parts list, is available from Power
Integrations in design note DN-15, TOPSwitch
Power Line Transceiver. This design note is available on the Power Integrations
web site at http://www.powerint.com, or it can be ordered from Power Integrations
at the following address:

Power Integrations, Inc.
477 North Mathilda Avenue
Sunnyvale, CA 94086
Phone: [phone] or 1-800-552-3155
Fax: [phone]

Building a power supply using DN-15 greatly simplifies the task of developing a
switching supply-based PLT-22 node since an instance of this design has been
verified to meet all of the impedance and noise requirements documented in this
chapter. Even though it is necessary to re-verify noise performance (due to
variations in PCB layout), using a predesigned/preverified supply significantly
reduces development time relative to a custom switching supply.

®

Power Supply for Echelon PLT-21

pins

LONWORKS PLT-22 Transceiver's User Guide 5-21

Off-the-Shelf Switching Supplies

Most commercially available switching power supplies have been designed with some
level of input noise filtering. Frequently this level of filtering is adequate if the supply’s
fundamental switching frequency is within the optimal ranges of Table 5.4 over all
operating conditions and tolerances. Supplies with other fundamental operating
frequencies may be able to meet the required noise masks of the previous sections with
greater effort and/or cost; however, meeting the noise mask requirements with a power
supply fundamental frequency (or second or third harmonic) in the 110kHz to 140kHz
range is very challenging and not recommended.

Most off-the-shelf switching supplies have a very low input impedance and require the
addition of an input inductor as shown in figure 5.5.

Custom Switching Supplies

Design of a custom switching supply, even one which employs a commerically
available controller chip, is very challenging and is only recommended if none of
the other options outlined in this chapter are suitable. If this option is chosen, it
is recommended that it only be pursued by experienced switching supply and
electromagnetic compatibility experts. Even if such personnel are available,
extra time must be allowed for design iterations during development. If this
approach is chosen, it is absolutely essential that the supply is verified to meet
the input and output noise masks of this chapter.

!

Note that many of the popular power supply designs documented by National
Semiconductor in conjuntion with their Simple Switcher™ controller chips do
not meet the required noise masks. Due to their very wide frequency tolerance,
the use of any Simple Switcher controller with a rated operating freqeuncy of
52kHz, 100kHz, or 150kHz is not recommended (e.g., LM2574, LM2575, LM2576,
LM2577, LM2585, LM2587, LM2594, LM2595, LM2596, LM2597, LM2598,
LM2599, LM1575, LM1577). Other Simple Switcher controller chips with
nominal operating frequencies of 200kHz or higher may be considered, providing
the design has been verified to meet the input and output noise mask
requirements of this chapter (over all of the operating conditions).

5-22 Power Supplies for the PLT-22 Transceiver

6

Design and Test for Electromagnetic

Compatibility

This chapter includes discussions of radiated electromagnetic
interference (EMI) and electrostatic discharge (ESD) design practices
for products containing the PLT-22 transceiver. These design practices
help the designer to create a product with the required
Electromagnetic Compatibility (EMC).

LONWORKS PLT-22 Transceiver User’s Guide 6-1

EMI Design Issues

The high-speed digital signals associated with microcontroller designs can generate
unintentional electromagnetic interference (EMI). High-speed voltage transitions
generate RF currents that can radiate from a product if a nearby length of wire or
piece of metal acts as an antenna.

Products that use a PLT-22 transceiver together with a Neuron Chip will generally
need to demonstrate compliance with EMI limits enforced by various regulatory

agencies. In the USA, the FCC
Part 15 level “A” for industrial products, and level “B” for consumer and household
products. Most European countries require compliance to CENELEC EN 50065-1.
Similar regulations are imposed in most countries throughout the world.

In addition to the following discussion, designers of PLT-22 transceiver-based nodes
are strongly encouraged to read reference [11] for a good treatment of EMC. The

EDN Designer's Guide to EMC

EMC issues.

Designing Systems for EMC (Electromagnetic Compatibility)

Careful PCB layout is important to ensure that a PLT-22 transceiver-based node will
achieve the desired level of EMC. A typical PLT-22 transceiver-based node will have
several digital signals switching in the 1MHz-10MHz range. These signals will
generate both voltage noise near the signal traces, and current noise in the signal
and power supply traces. The goal of good node design is to keep voltage and current
noise from coupling out of the product enclosure.

6

requires that unintentional radiators comply with

12

is also a good source of design advice regarding

It is very important to minimize the “leakage” capacitance from circuit traces in the
node to any external metal near the node because this capacitance provides a path
for the digital noise to couple out of the product enclosure. Figure 6.1 shows the
leakage capacitances to earth ground from a node's logic ground (C

from a digital signal line in the node (C

leak,SIGNAL

). If the PLT-22 transceiver-

leak,GND

) and

based node is housed inside a metal chassis, then that metal chassis will probably
have the largest leakage capacitance to other nearby pieces of metal. If the node is
housed inside a plastic package, then PCB ground guarding must be used to
minimize C

reduces C

leak,SIGNAL

leak,SIGNAL

. Effective guarding of digital traces with logic ground

significantly, which in turn reduces the level of common-mode

RF currents driven onto the AC mains.

When a node is mounted near a piece of metal, especially metal that is earth
grounded, any leakage capacitance from fast signal lines to that metal will provide a
path for RF currents to flow. When V

of logic ground with respect to earth ground will increase slightly. When V
up to V
As C

leak,SIGNAL

, logic ground will be pushed down slightly with respect to earth ground.

DD5

increases, a larger current flows during V

is pulled down to logic ground, the voltage

gate

gate

transitions,

gate

pulls

generating more common-mode RF current. This common-mode RF current can
generate EMI in the 30MHz-300MHz frequency band, thereby exceeding
FCC/CENELEC levels, even when C

leak,SIGNAL

from a clock line to earth ground is

less than 1pF. This means that it is essential to guard the clock lines.

6-2 Design and Test for Electromagnetic Compatibility

V

V

DD5

DD5

Power
Mains

L

N

g

t

n

i

i

l

u

p

c
r

u

i

o

C

C

"CHASSIS"

GND

Vgate

C decouple

C load

PLT-22 and Power Supply

GND

C leak,CHASSIS

Figure 6.1 Parasitic Leakage Capacitances to Earth Ground

Node
Logic
Ground

C leak,GND

Leakage
Capacitances to
Earth Ground

C leak,SIGNAL

From this discussion, it is apparent that minimizing C

leak,SIGNAL

By using 0.1µF or 0.01µF decoupling capacitors at each digital IC power pin, V

is very important.

DD5

and logic ground noise can be reduced. Logic ground can then be used as a ground
shield for other noisy digital signals and clock lines.

For example, in most PLT-22 transceiver-based nodes that use the Neuron 3120
Chip, the fastest digital signal on the PCB is the CKOUT line from the PLT-22
transceiver to the Neuron Chip. If a two-layer PCB is being used, CKOUT can be
routed to the Neuron Chip with ground guard traces straddling the clock trace on the
component side of the board, and a wide ground trace (or ground plane) covering the
underside of the clock trace on the solder side of the PCB. If a four-layer PCB is
used, the clock trace can be moved to an inner layer and guarded on all four sides.
The CKOUT line from the PLT-22 transceiver to the Neuron Chip should be as short
as practical, and in all cases ≤ 50mm (2").

Since the Neuron 3150 Chip has an external memory interface bus, there are many
more traces in a node using a Neuron 3150 Chip that need to be guarded by logic
ground. In addition, the V

ROM/RAM components requires more V
layer PCB to maintain RF-quiet V

noise generated by the memory interface and external

DD5

decoupling, and may require a four-

DD5

and logic ground lines.

DD5

LONWORKS PLT-22 Transceiver User’s Guide 6-3

In summary, the following general rules apply:

• the faster the Neuron Chip clock speed, the higher the level of EMI;

• better V
lowers EMI;

• the Neuron 3120 Chip generates less EMI than the Neuron 3150 Chip since the
Neuron 3120 Chip has no external memory interface lines;

• a four-layer PCB generates less EMI than a two-layer PCB since the extra layers
facilitate better V

• a two-layer PLT-22 transceiver-based node using on a Neuron 3120 Chip
operating at 5MHz should be able to meet FCC/CENELEC EMC if good
decoupling and ground guarding of the CKOUT line are used.

Early testing of prototype circuits at an outdoor EMI range should be used to
determine the effectiveness of these EMC techniques.

DD5

ESD Design Issues

Electrostatic discharge (ESD) is encountered frequently in industrial and commercial
use of electronic systems

requirements for ESD testing in product qualifications analogous to the present EMI
requirements

decoupling quiets RF noise at the sources (the digital ICs), which

decoupling and more effective logic ground guarding;

DD5

10

. In addition, the European Community has adopted

13

under the EMC directive.

Reliable system designs must consider the effects of ESD and take steps to protect
sensitive components. Static discharges occur frequently in low-humidity
environments when operators touch electronic equipment. Keyboards, connectors,
and enclosures may provide paths for static discharges to reach ESD sensitive
components such as the Neuron Chip and the PLT-22 transceiver. This section
describes the issues involved in designing ESD immunity into PLT-22 transceiver­based products.

In addition to the following discussion, designers of PLT-22 transceiver-based nodes
are strongly encouraged to read references [10] and [12]. The EDN Designer's Guide

12

to EMC

return currents.

is especially helpful in understanding the importance of managing ESD

Designing Systems for ESD Immunity

There are two general methods that are used to protect products from ESD. The first
is to seal the product to prevent static discharges from reaching the sensitive circuits
inside the package. The second method involves grounding circuits so that ESD hits
to user-accessible metal parts can be shunted around any sensitive circuitry.

For safety reasons, PLT-22 transceiver-based nodes that communicate on the AC
mains generally do not have a user-accessible network connection. The network
connection may be accessible on nodes that communicate on low-voltage (<42.4V) or
unpowered lines. The product's package should be designed to minimize the
possibility of ESD hits arcing into the node's circuit board. If the product's package

6-4 Design and Test for Electromagnetic Compatibility

is plastic, then the PCB should be supported in the package so that unprotected
circuitry on the PCB is not adjacent to any seams in the package. The PCB should
not touch the plastic of an enclosure near a seam, since a static discharge can "creep"
along the surface of the plastic through the seam and arc onto the PCB.

Once an ESD hit has arced to the product, the current from the discharge will flow
through all possible paths back to earth ground. Proper use of ground traces
combined with the protection of user-accessible circuitry will permit ESD return
currents to flow back to earth ground without disrupting the normal operation of the
Neuron Chip and other node circuitry. Generally, this means that the ESD currents
should be shunted to the center of a star ground configuration and then out to a
chassis or earth ground connection. The location of the star ground center should be
such that the shunted current doesn't pass through, or close to, the Neuron Chip or
other sensitive components. If the node is floating with respect to earth ground, then
the ESD current will return capacitively to earth via the power supply wires and/or
the PCB ground plane.

Explicit clamping of user-accessible circuitry is required to shunt ESD currents from
that circuitry to the center of the star ground on the PCB. For example, if the
Neuron Chip in a PLT-22 transceiver-based node is scanning a keypad using I/O
lines, then the I/O lines to that keypad will need to be diode-clamped as shown in
figure 6.2. If a negative ESD hit discharges into the keypad, the diode clamps to
ground shunt the ESD current into the ground plane. If a positive ESD hit
discharges into the keypad, the V

diodes shunt the current to the ground plane

DD5

via a 0.1µF decoupling capacitor that is placed directly adjacent to the clamp diodes.
The keypad connector, diodes and decoupling capacitor should all be located close to
the center of the star ground so that ESD current does not pass through sensitive
circuitry as it exits from the PCB.

Keypad

+5V

I/O

Lines

MMAD1103 Diode Array

(or BAV99/1N4148 Equivalent Diodes)

Figure 6.2 Illustration of I/O Line ESD Clamps

+5V

Neuron

Chip

LONWORKS PLT-22 Transceiver User’s Guide 6-5

Conducted Emissions Testing

The PLT-22 transceiver is designed to comply with both FCC Section 15.107 "Limits
for carrier current systems" and CENELEC EN 50065-1 “Signaling on low-voltage
electrical installations in the frequency range 3kHz to 148.5kHz” Part 1 “General
requirements, frequency bands and electromagnetic disturbances”.

Many commercial testing laboratories lack experience measuring conducted
emissions of intentional power line communicators, and commonly-applied testing
procedures will give erroneous measurement results. Proper measurement of
conducted emissions to verify compliance with FCC and CENELEC EN 50065-1
requires strict adherence to the following guidelines.

• Connect the product under test to the correct network for measurement. For

both FCC and CENELEC EN 50065-1 measurements, use the
50Ω//(50µH+5Ω) Line Impedance Stabilization Network (LISN) as specified in
CISPR Publication 16

• Care must be taken to ensure that the PLT-22 transceiver's transmit signal

does not overload the measurement apparatus. Typically, an attenuator must
be installed at the input to the measuring receiver, i.e., spectrum analyzer, to
avoid erroneous results due to instrumentation overload. A test for
determining whether or not the results are being distorted due to overload is
as follows: measure the emissions, then increase the attenuation between the
product under test and the measuring receiver, and then re-measure
emissions. There is an overload problem if the level of emissions at
frequencies other than the main carrier has decreased by more than the
increase in attenuation. Most spectrum analyzers have a built-in input
attenuator. If this is the case, the attenuator setting is usually taken into
account by the instrument. Consequently, the reported levels should not
change when the spectrum analyzer input attenuation is changed. There is
an overload problem if a level change is reported at frequencies other than the
main carrier frequency.

(9)

, second edition.

• Care must be taken to ensure that the residual noise floor of the entire

measurement set remains at least 10dB below the specification limit once the
appropriate attenuator is installed. That is, a noise floor less than 38dBµV for
FCC measurements, and a noise floor less than 36dBµV for CENELEC EN
50065-1 measurements.

• The measurements must be made with the specified detector. For both FCC

and CENELEC EN 50065-1 measurements, use the quasi-peak detector and
the average detector as specified in CISPR Publication 16. Although a scan
with a peak detector is common because it may be performed quickly, the
limits specified by FCC Section 15.107 and by CENELEC EN 50065-1 are for
quasi-peak and average detectors only. For power line transceivers, peak
measurements often appear erroneously high relative to the quasi-peak
limits.

• The measurements must be made with the specified filter. For FCC

measurements, a 9kHz bandwidth filter is specified. For CENELEC EN
50065-1 measurements, a 200Hz bandwidth filter is specified for

6-6 Design and Test for Electromagnetic Compatibility

measurements below 150kHz, and a 9kHz bandwidth filter is specified above
150kHz.

• For FCC measurements, an input filter which meets the requirements of

CISPR 16 is suitable. The CENELEC EN 50065-1 specification requires that
the filter inside the measuring receiver have even steeper filter skirts than
the minimum required by CISPR 16.

CENELEC EN 50065-1 specifies a 9kHz filter for measurements above 150kHz. The
allowable transmit level is +116dBµV between 95kHz and 140kHz (+134dBµV in
some applications). The CENELEC EN 50065-1 specification limit is +66dBµV
quasi-peak at 150kHz. To make a proper measurement, the filter inside the
measuring receiver must have filter skirts providing at least 60dB of attenuation
10kHz from its center.

The CENELEC EN 50065-1 sub-committee SC 105A (Mains Communicating
Systems) recognized the need for a filter with steeper skirts than the minimum
specified by CISPR Publication 16. As stated in a final draft of an amendment to EN
50065-1 dated January, 1994, "the measuring instrument defined by the minimum
requirements of CISPR 16 is unsuitable for the measurement of mains signaling
equipment that uses a signaling frequency not far below 150kHz," and the sub­committee SC 105A agreed that "the proper solution would be to specify the
attenuation characteristic of the measuring receiver more closely, receivers being
known to be available on the market."

1

EN 50065-1 Amendment AC specifies a filter
that still complies with CISPR 16 but which has steeper filter skirts. Many spectrum
analyzers, even very expensive ones, do not meet this requirement.

The Rohde&Schwarz EMI Test Receiver ESHS30 has been found to have adequate
filter skirts. Although its specification does not guarantee adequate filter skirts, two
samples of the ESHS30 test receiver were found to make the measurement reliably.

In addition, care must be taken in setting up the Rohde&Schwarz EMI Test Receiver
ESHS30. The "automatic" mode for setting input attenuation selects an incorrect
attenuation level that will result in an overload condition, which is not properly
reported by the overload indicator on the Test Receiver. The proper attenuation
must be selected using manual mode. A set-up program to accurately run scans for
CENELEC EN 50065-1 compliance testing on the Rohde&Schwarz EMI Test
Receiver ESHS30 is available from Echelon's L

ONWORKS Developer's Toolbox at

www.echelon.com/toolbox.

5

An application note from Hewlett-Packard

describes a test method for performing
EN 50065-1 conducted emissions tests using Hewlett-Packard EMI test receivers.
The title of the application note is “Conducted Emissions Measurements on Power
Line Transceiver Products.” This application note describes an “off-the-shelf”
external filter and a methodology that allows the measurements specified in EN
50065-1 to be performed accurately.

If the unit under test is found to exceed the applicable conducted noise limit at
frequencies above 500kHz, it may be the result of unintentional coupling from the
node's various digital circuits. If this occurs, improvements in grounding and printed
circuit layout are generally required. Refer to Chapter 4 for a discussion of how to
avoid coupling circuit stray field pickup.

LONWORKS PLT-22 Transceiver User’s Guide 6-7

In some instances conducted emissions above 500kHz can be adequately reduced by
the addition of a small value capacitor (e.g., ≤470pF) either across the AC mains or
from the line conductor to ground. While nodes using the PLT-22 transceiver have
been demonstrated to pass various limits without an additional capacitor, variations
in node design and layout may require the addition of this small value capacitor. If a
capacitor is added across the line it should be an X2 safety-rated type for maximum
surge reliability. If capacitors are added from either line or neutral to earth, they
should be Y safety rated. Alternately, this capacitor can be added across coupling
circuit inductor L1 (see figures 4.10 and 4.13) or across the secondary winding of
transformer T1 (see figures 4.11 and 4.14). If this option is chosen, either a
metalized polyester capacitor ≥250VDC, a ceramic 1000VDC capacitor, or a Y-type
capacitor should be used for surge reliability.

Adding capacitance in any of the above locations reduces the input impedance of the
node and could therefore cause an increase in communication signal attenuation.
The maximum value of capacitance which can be added without significantly
affecting attenuation depends on the application. Table 6.1 shows the maximum
value of added capacitance by application. Under no circumstances should

capacitors >5000pF be used since they will result in excessive signal
attenuation.

Table 6.1 EMC Suppression Capacitor Value versus Application

Application Network Impedance @

130kHz

Single building AC

1-20 Ohms ≥ 250 Ohms ≤ 4700pF

Capacitor Impedance @

130kHz

Capacitor Value

mains

Dedicated cable

50 - 100 Ohms ≥ 1000 Ohms ≤ 1200pF

≤100 nodes

≤100m

Dedicated cable

50 - 100 Ohms ≥ 2500 Ohms ≤ 470pF

>100 nodes

>100m

Another common method of EMC suppression, the addition of ferrite beads, is
generally unacceptable if they are placed anywhere in the transmit signal path.
Most ferrite beads have several Ohms of impedance at 130kHz. The impedance of
any element placed in series with the transmit signal or return path must be
significantly less than 1 Ohm as described in chapter 4. There is, however, one
means whereby a ferrite bead can be used to reduce common mode high frequency
emissions without affecting the transmit signal. If both the communication signal
and its return conductor (i.e., Line and Neutral for L-to-N coupling or Line and Earth
for L-to-E coupling) pass through the same bead in a common fashion, the bead will
not add any series impedance to the transmitter. This is true since the signal
currents in the two conductors produce opposite polarity (canceling) flux in the
ferrite bead’s core. Common mode noise of equal polarity on both conductors will
produce additive flux in the ferrite bead’s core and will thus be attenuated. Figure

6.3 illustrates both acceptable and unacceptable ferrite bead topologies.

6-8 Design and Test for Electromagnetic Compatibility

PLT-22

Coupling

Circuit

Unacceptable Topology

Power

Mains

PLT-22

Coupling

Circuit

Unacceptable Topology

PLT-22

Coupling

Circuit

Unacceptable Topology

PLT-22

Coupling

Circuit

Acceptable Topology

Figure 6.3 Ferrite Bead Topologies

Power

Mains

Power

Mains

Power

Mains

LONWORKS PLT-22 Transceiver User’s Guide 6-9

6-10 Design and Test for Electromagnetic Compatibility

7

Communication Performance

Verification

This chapter describes procedures to verify basic communication
performance of products based on the PLT-22 transceiver.

LONWORKS PLT-22 Transceiver User’s Guide 7-1

Why Verify Communication Performance?

While each PLT-22 transceiver is verified to meet its full communication
performance capabilities prior to shipment, circuitry external to the transceiver
could compromise the communication performance of the node in which the
transceiver is used. Ways in which communication performance could be
compromised include mis-loaded components, inadequately filtered switching power
supplies, circuitry improperly added between the transceiver's coupling circuit and
the power mains, and deviations from recommended part specifications. Due to the
robust communication capability of the transceiver, it may not be obvious that
communication performance has been compromised when testing in a nominal
environment.

Since compromised performance is generally observable only under
“corner-case” conditions, failure to verify performance prior to deployment
could result in many marginal units in the field before a problem is
detected. It is therefore essential that the communication performance of
every PLT-22-based design be verified prior to field deployment. This can be

accomplished either by self verification, using the procedures given in this chapter,
or by contacting your Echelon sales representative to make arrangements to send the
node to Echelon for confidential evaluation.

This chapter describes a simple "black box" testing methodology for determining
whether or not the communication performance of a PLT-22 transceiver-based
product has been compromised. This procedure works equally well for products
employing L-N or L-E coupling.

Before starting the verification process it is essential that the checklist in
Appendix B be completed in its entirety.

Verification Strategy

An overview of the recommended verification procedure is as follows:

1 Create a controlled power line environment that is isolated from typical power

mains noise and loading.

2 Provide known load impedances at the PLT-22 transceiver's communication

frequencies.

3 Use the PLCA-22 Power Line Communications Analyzer (model 58022) as a

calibrated reference transmitter and receiver.

4 Test the performance independent of the product's application by making use

of the Neuron Chip service pin and internal statistics features. If the product
under test does not have a service pin switch then it will need to be added to
the product for testing purposes.

5 Test for unintentional noise injection and excessive loading by the product

under test. This is to ensure that the device can behave as a “good citizen” on a
power line network.

7-2 Communication Performance Verification

6 Verify that the product's transmit signal level is within acceptable limits. This

is done by deliberately loading the isolated power mains on which the product
under test is operating and comparing the output transmission level under load
against a reference level.

7 Verify that the product's receive sensitivity is within acceptable limits. This is

performed using a pair of PLCA-22 analyzers. The communication signal level
of the transmitting PLCA-22 analyzer is gradually decreased and the receive
performance of the product under test is monitored and compared against
reference performance levels.

Power Line Test Isolator

The circuit shown in figure 7.1 is used to create a power mains environment that is
isolated from the noise and loading present on typical power mains. When properly
constructed, the circuit provides 60 to 80dB of isolation between the power mains
and the product under test at the PLT-22 transceiver’s communication frequencies.
The effectiveness of the circuit should be verified by using a pair of PLCA-22
analyzers communicating between the power mains input and the output. To
perform this verification, set the PLCA-22 analyzer that is connected to the input
side of the isolator to send packets at 3.5Vpp in UnackPri mode in the C band. The
green bargraph meter on the receiving analyzer (connected to the “product under
test” output) should indicate a signal strength no higher than –60dB. Without any
packet transmission, no LEDs above the –78dB primary and secondary signal
strength LEDs should be illuminated or flashing. Note that Neon power indicators
should not be used on the isolated output, since they frequently produce noise in the
–72dB range.

Since the isolator does not completely block communications from other PLT-22
transceivers communicating on the power mains, receive testing must only be
performed when there is no other packet activity on the power mains.

Line in

From power

mains

Neutral in

Earth

Line out

C

R

C

R

C

R

All capacitors 0.47µF 250VAC (X2 type)

All resistors 20ž 1 Watt ±5%, unless otherwise indicated

Isolation transformer rating based on load requirements

CC

C

C

50 ž

±5%, 1/4W

To product

under test

Neutral out

Earth

Figure 7.1 Power Mains Isolation Circuit

LONWORKS PLT-22 Transceiver User’s Guide 7-3

The transformers shown in the circuit are 50/60 Hz, 1:1 isolation transformers. The
load (VA) rating of each transformer should be chosen based on the load
requirements of the devices under test. Care should be taken when wiring the
isolator to avoid inadvertent signal coupling between the input and output wiring by
spacing the input and output wires at least 15cm (6") apart.

Test Equipment

In addition to the power mains isolator described in the previous section, the
following “off-the-shelf” equipment will be needed for testing:

• One pair of PLCA-22 Power Line Communications Analyzers (Model 58022).

PLCA-21 Power Line Communication Analyzers are not able to test the
secondary operating frequency of the PLT-22 transceiver and are not
recommended for this test. The PLCA-21 lacks the features required to perform
these tests accurately and should not be used.

• One PL-20 Line-to-Neutral power line coupler, Echelon model 78200-221.

• Two 50Ω coax cables approximately 25cm (12") long with male BNC connectors

on both ends (AMP 1-221128-x or equivalent).

• A power strip, equipped with both a circuit breaker and 4 or more outlets, which

does not include either surge protection, neon lights, or noise isolation circuitry.

The following additional equipment will need to be constructed for testing:

• A "5Ω load" circuit, as shown in figure 7.2, should be built in a suitable enclosure

and provided with an appropriate male AC mains plug. Note that the 1MΩ
resistor’s stand-off voltage should be greater than or equal to the peak line
voltage.

L

N

E

1Mž,
±5%,
1/4W

open

0.47µF ±10%, 250VAC (X2 type)

4.7ž ±5%,1W

Figure 7.2 "5Ω load" Circuit

7-4 Communication Performance Verification

• A "7Ω load" circuit, as shown in figure 7.3, should be built in a suitable enclosure

and provided with an appropriate male AC mains plug. Note that the 1MΩ
resistor’s stand-off voltage should be greater than or equal to the peak line
voltage.

L

N

E

1Mž,
±5%,
1/4W

open

0.47µF ±10%, 250VAC (X2 type)

6.8ž ±5%, 1W

Figure 7.3 "7Ω load" Circuit

• An impedance circuit shown in figure 7.4 should be built in a suitable enclosure

with bulkhead BNC jacks (AMP 413771-x or equivalent). This impedance circuit,
placed in series with the output path of a PLCA-22 analyzer, effectively increases
its output impedance. This will allow for a more sensitive measurement of the
receive mode impedance of the product under test.

88.7ž ±1%, 1/4W

Figure 7.4 Impedance Circuit Used For Excessive Loading Verification

• An attenuation circuit shown in figure 7.5 should be built in a suitable enclosure

with bulkhead BNC jacks (AMP 413771-x or equivalent). This attenuation
circuit, or "pad", will provide approximately 60dB of attenuation when connected
into the receive performance verification set-up of figure 7.9.

30.1kž ±1%, 1/4W

Figure 7.5 Attenuation Circuit Used For Receive Performance Verification

LONWORKS PLT-22 Transceiver User’s Guide 7-5

For the receive performance verification, a PC running nodetuil.exe (available on
Echelon’s web site in the Developer’s Toolbox at www.echelon.com/toolbox) is
required. The Node Status command will be used to obtain a record of the number of
uncorrupted packets received by the Unit Under Test (UUT). This set-up will be
described in detail in a later section.

Good Citizen Verification

Use the following steps to verify that the Unit Under Test (UUT) does not inject
unwanted noise onto the power mains or excessively load the power mains.

Unintentional Output Noise Verification

The following procedure determines if the UUT is generating unwanted noise which
may hinder its communication performance or that of other devices on the power
mains.

1 Connect a single PCLA-22 analyzer, the UUT, and the Isolator as shown in

figure 7.6. Verify that the anlayzer is set for C-band operation by observing the
selected band in the upper right-hand corner of the LCD display (if it is set for
A-band, then it must be changed to C-band using the Setup screen of the
anlayzer). Leave the PLCA-22 analyzer in idle mode (no packets being
transmitted) and set it for Internal and Line-to-Neutral coupling (coupling mode
switch to the right).

2 Verify that the UUT application program is not sending messages.

3 Observe the signal strength bar graph LEDs. None of the LEDs, above

the -72dB LED, should be flashing on either the primary or secondary bar graph
meters. In addition, the Packet Detect (PKD) LEDs should not flash any more
than once per minute.

7-6 Communication Performance Verification

PLCA-22

Unit Under Test

(UUT)

service pin

packet detect LED

To power
mains

Recv

C-band

ISOLATOR

Isloated Power Line

Figure 7.6 Unintentional Output Noise Verification

If any of the signal strength LEDs, above the -72dB LEDs, flash, or the PKD LEDs
flashes more than once per minute, then excessive noise or interference is present.
This could be caused by one or more of the following sources:

• The UUT is generating unwanted noise internally. This is most often associated

with on-board switching power supplies. If the UUT includes a switching power
supply, verify that the power supply noise masks of Chapter 5 have been met.

• Power line communications signals present on the power input side of the isolator

are not sufficiently attenuated. Ensure that no other power line signaling equipment
is operating on the power mains when performing this test.

• The isolator is not completely isolating the test set-up from noise on the power

mains. Verify the effectiveness of the isolator as described earlier.

The source of this noise or interference must be identified and eliminated before
proceeding with verification testing.

Excessive Loading Verification

The procedure described in this section is used to determine if the receive mode
impedance of the UUT is greater than approximately 100Ω at 132kHz (as it should
be). A receive mode impedance of less than 100Ω could cause excessive signal
attenuation resulting in impaired reception by both the UUT and its neighboring

LONWORKS PLT-22 Transceiver User’s Guide 7-7

nodes. For applications which require an even higher receive impedance, refer to
discussions in Chapters 5 and 6.

The 10Vp-p output capability of the PLCA-22 analyzer is used to increase the
sensitivity of the test. The higher output signal allows the 0dB, -3dB, and -6dB
LEDs of the PLCA-22 analyzer signal strength meter to be used for observing signal
strength. These LEDs, unlike the other LEDs in the signal strength meter, are only
3dB apart allowing for better measurement resolution.

A series impedance circuit (figure 7-4) in the output path of the transmitting PLCA­22 analyzer is used to increase its effective output impedance, thereby preventing its
normally low transmit output impedance from overshadowing the impedance of the
product under test.

1 Set a PLCA-22 analyzer in Recv, UnackPri, and C-band modes (referred to as

the Recv PLCA-22 analyzer) and configured for Internal and Line-to-Neutral
coupling, as shown in figure 7.7.

2 Connect a second PLCA-22 analyzer in Send, UnackPri, and C-band modes

(referred to as the Send PLCA-22 analyzer) and set it for External and Line-to­Neutral coupling as shown in figure 7.7. Connect the impedance circuit (88.7Ω
resistor; figure 7-4) and the coupling circuit as shown. This test is best conducted
with the CENELEC protocol turned off in order to provide uninterrupted LED
illumination (set on the send unit's setup screen).

3 Verify that Attn on the SPHY PLCA-22 analyzer is set to 0. Set the number of

packets to be transmitted to 9999k on that unit and set the packet length to 13
bytes. Set TxVpp: 10V.

4 Without the UUT connected, press START on the Send PLCA-22 analyzer. A test

should begin and the receive packet count on the Recv PLCA-22 analyzer should
increment with a packet error rate very close to 0%. The signal strength meter on
the Recv PLCA-22 analyzer should have the LEDs up to and including the -3dB
primary signal strength LED illuminated. The 0dB primary LED may or may not
be flashing.

5 Next, connect the UUT as shown in figure 7.7. The -3dB primary signal strength

LED on the Recv PLCA-22 analyzer either should be flashing or illuminated
continuously. If the -3dB primary LED is extinguished, then the UUT's input
impedance is excessively low (<100Ω). The impedance of the UUT must be
corrected before proceeding; refer to the node checklist described in Appendix B
for assistance.

7-8 Communication Performance Verification