Cirrus Logic CDB5490U User Manual

CDB5490U

CDB5490U Engineering Board and GUI Software

Features

• Standalone Power Meter Application

• Voltage and Current Interfaces

• Low- and High-voltage Sensor Connections

• Adaptable Sensor Filters Onboard

• USB Communication with PC

• Isolated UART Communication

• Onboard C8051F342 Microcontroller

• Single Supply Operation from USB or an External +5 V DC
Supply

• Onboard DC-DC Converter and Regulator

• LCD Power Monitor Display

• LabWindows

– Full Register Setup and Chip Control
– Simplified Register
– Quick Calibration Control
– FFT Analysis
– Time Domain Analysis
– Noise Histogram Analysis

• Voltage Reference Access

®

/ CVI® GUI Software

General Description

The CDB5490U is an extensive tool designed to evaluate the
functionality and performance of Cirrus Logic’s CS5490 power
measurement device.

Multiple analog input connection options, configuration input fil­ters, direct and isolated digital interfaces, multiple power supply
options, an onboard programmable microcontroller, visual LEDs
with an LCD panel make the board a flexible and powerful cus­tomer development tool for various power measurement
applications.

The GUI software provides easy and complete access and con­trol to the onboard CS5490 device. In addition, it includes the
function of raw ADC data collection with time domain, frequency
domain, and histogram analysis.

Schematics in PADS™ PowerLogic™ format are available for
download at http://www.cirrus.com/en/support

ORDERING INFORMATION

CDB5490U-Z Evaluation Board

.

Cirrus Logic, Inc.

http://www.cirrus.com

Copyright  Cirrus Logic, Inc. 2012

(All Rights Reserved)

APR‘12

DS923DB5

CDB5490U

IMPORTANT SAFETY INSTRUCTIONS

Read and follow all safety instructions prior to using this demonstration board.

This Engineering Evaluation Unit or Demonstration Board must only be used for assessing IC performance in a
laboratory setting. This product is not intended for any other use or incorporation into products for sale.

This product must only be used by qualified technicians or professionals who are trained in the safety procedures
associated with the use of demonstration boards.

Risk of Electric Shock

• The direct connection to the AC power line and the open and unprotected boards present a serious risk of electric
shock and can cause serious injury or death. Extreme caution needs to be exercised while handling this board.

• Avoid contact with the exposed conductor or terminals of components on the board. High voltage is present on
exposed conductor and it may be present on terminals of any components directly or indirectly connected to the AC
line.

• Dangerous voltages and/or currents may be internally generated and accessible at various points across the board.

• Charged capacitors store high voltage, even after the circuit has been disconnected from the AC line.

• Make sure that the power source is off before wiring any connection. Make sure that all connectors are well

connected before the power source is on.

• Follow all laboratory safety procedures established by your employer and relevant safety regulations and guidelines,
such as the ones listed under, OSHA General Industry Regulations - Subpart S and NFPA 70E.

Suitable eye protection must be worn when working with or around demonstration boards. Always

comply with your employer’s policies regarding the use of personal protective equipment.

All components and metallic parts may be extremely hot to touch when electrically active.

Contacting Cirrus Logic Support

For all product questions and inquiries contact a Cirrus Logic Sales Representative. To find the one nearest to you
go to www.cirrus.com

IMPORTANT NOTICE

Cirrus Logic, Inc. and its subsidiaries ("Cirrus") believe that the information contained in this document is accurate and reliable. However, the information is subject
to change without notice and is provided "AS IS" without warranty of any kind (express or implied). Customers are advised to obtain the latest version of relevant
information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale
supplied at the time of order acknowledgment, including those pertaining to warranty, indemnification, and limitation of liability. No responsibility is assumed by Cirrus
for the use of this information, including use of this information as the basis for manufacture or sale of any items, or for infringement of patents or other rights of third
parties. This document is the property of Cirrus and by furnishing this information, Cirrus grants no license, express or implied under any patents, mask work rights,
copyrights, trademarks, trade secrets or other intellectual property rights. Cirrus owns the copyrights associated with the information contained herein and gives
consent for copies to be made of the information only for use within your organization with respect to Cirrus integrated circuits or other products of Cirrus. This con­sent does not extend to other copying such as copying for general distribution, advertising or promotional purposes, or for creating any work for resale.

CERTAIN APPLICATIONS USING SEMICONDUCTOR PRODUCTS MAY INVOLVE POTENTIAL RISKS OF DEATH, PERSONAL INJURY, OR SEVERE PROP­ERTY OR ENVIRONMENTAL DAMAGE ("CRITICAL APPLICATIONS"). CIRRUS PRODUCTS ARE NOT DESIGNED, AUTHORIZED OR WARRANTED FOR
USE IN PRODUCTS SURGICALLY IMPLANTED INTO THE BODY, AUTOMOTIVE SAFETY OR SECURITY DEVICES, LIFE SUPPORT PRODUCTS OR OTHER
CRITICAL APPLICATIONS. INCLUSION OF CIRRUS PRODUCTS IN SUCH APPLICATIONS IS UNDERSTOOD TO BE FULLY AT THE CUSTOMER'S RISK
AND CIRRUS DISCLAIMS AND MAKES NO WARRANTY, EXPRESS, STATUTORY OR IMPLIED, INCLUDING THE IMPLIED WARRANTIES OF MERCHANT­ABILITY AND FITNESS FOR PARTICULAR PURPOSE, WITH REGARD TO ANY CIRRUS PRODUCT THAT IS USED IN SUCH A MANNER. IF THE CUSTOMER
OR CUSTOMER'S CUSTOMER USES OR PERMITS THE USE OF CIRRUS PRODUCTS IN CRITICAL APPLICATIONS, CUSTOMER AGREES, BY SUCH USE,
TO FULLY INDEMNIFY CIRRUS, ITS OFFICERS, DIRECTORS, EMPLOYEES, DISTRIBUTORS AND OTHER AGENTS FROM ANY AND ALL LIABILITY, IN­CLUDING ATTORNEYS' FEES AND COSTS, THAT MAY RESULT FROM OR ARISE IN CONNECTION WITH THESE USES.

Cirrus Logic, Cirrus, the Cirrus Logic logo designs, EXL Core, and the EXL Core logo design are trademarks of Cirrus Logic, Inc. All other brand and product names
in this document may be trademarks or service marks of their respective owners.LabWindows and CVI are registered trademarks of National Instruments, Inc.

Windows, Windows 2000, Windows XP, and Windows 7 are trademarks or registered trademarks of Microsoft Corporation.

PADS and PowerLogic are trademarks of Mentor Graphics Corporation.

2 DS923DB5

CDB5490U

TABLE OF CONTENTS

1. HARDWARE .............................................................................................................................................. 5

1.1 Introduction ........................................................................................................................................ 5

1.2 Evaluation Board Overview ................................................................................................................ 5

1.3 Analog Section ................................................................................................................................... 6

1.4 Digital Section .................................................................................................................................... 9

1.5 Power Supply Section ...................................................................................................................... 11

1.6 Typical Sensor Connections ............................................................................................................ 12

1.7 Standalone Meter Application .......................................................................................................... 15

2. SOFTWARE ............................................................................................................................................. 16

2.1 Installation Procedure ...................................................................................................................... 16

2.2 Using the Software ........................................................................................................................... 16

2.3 Start-up Window ............................................................................................................................... 17

2.4 Connect Menu .................................................................................................................................. 18

2.5 System Menu ................................................................................................................................... 19

2.6 Calibration Window .......................................................................................................................... 23

2.7 Conversion Window ......................................................................................................................... 25

2.8 Cirrus Test Window .......................................................................................................................... 27

Appendix A. Bill Of Materials .................................................................................................................... 37

Appendix B. Schematics............................................................................................................................. 39

Appendix C. Layer Plots ............................................................................................................................. 42

DS923DB5 3

CDB5490U

LIST OF FIGURES

Figure 1. CDB5490U Assembly Drawing and Default Configuration ................................................................ 5

Figure 2. Voltage Channel — Low-voltage Input .............................................................................................. 6

Figure 3. Voltage Channel — High-voltage Input ............................................................................................. 7

Figure 4. Current Channel — Low-voltage Input .............................................................................................. 8

Figure 5. MCU Connection Window ................................................................................................................. 9

Figure 6. Shunt Sensor Power Meter ............................................................................................................. 12

Figure 7. Current Transformer Power Meter................................................................................................... 13

Figure 8. Rogowski Coil Power Meter ............................................................................................................14

Figure 9. Standalone Power Meter Measurements ........................................................................................ 15

Figure 10. GUI Start-up Window..................................................................................................................... 17

Figure 11. Connect Menu Showing Successful USB Connection ..................................................................18

Figure 12. Connect Menu Showing Successful USB Connection ..................................................................18

Figure 13. USB Error Message....................................................................................................................... 18

Figure 14. Unknown Chip ID Error Message .................................................................................................. 19

Figure 15. System Pull-down Options ............................................................................................................ 19

Figure 16. Setup Window ............................................................................................................................... 20

Figure 17. Calibration Window........................................................................................................................ 23

Figure 18. Setup Window with 510638 Baud Rate ......................................................................................... 25

Figure 19. Conversion Collection Baud Rate Error.........................................................................................25

Figure 20. Conversion Window.......................................................................................................................26

Figure 21. Cirrus Test Pull-down Options....................................................................................................... 27

Figure 22. Data Collection Window ................................................................................................................ 28

Figure 23. Data Collection UART Error Message...........................................................................................28

Figure 24. Data Collection Output Window..................................................................................................... 29

Figure 25. Data Collection Configuration Window .......................................................................................... 30

Figure 26. Histogram Analysis........................................................................................................................ 32

Figure 27. FFT Analysis.................................................................................................................................. 33

Figure 28. Data Collection Window - Time Domain Analysis .......................................................................

Figure 29. Data Collection to File Window...................................................................................................... 35

Figure 30. Setup and Test Window ................................................................................................................ 36

Figure 31. Bill of Materials (Page 1 of 2) ........................................................................................................ 37

Figure 32. Bill of Materials (Page 2 of 2) ........................................................................................................ 38

Figure 33. Schematic - Analog Inputs............................................................................................................. 39

Figure 34. Schematic - CS5490 and Isolation ................................................................................................ 40

Figure 35. Schematic - Microcontroller and USB Interface............................................................................. 41

Figure 36. Top Silkscreen............................................................................................................................... 42

Figure 37. Top Routing ................................................................................................................................... 43

Figure 38. Bottom Routing.............................................................................................................................. 44

Figure 39. Solder Paste Mask ........................................................................................................................ 45

.. 34

4 DS923DB5

CDB5490U

Figure 1. CDB5490U Assembly Drawing and Default Configuration

1. HARDWARE

1.1 Introduction

The CDB5490U evaluation board provides a convenient means of evaluating the CS5490 energy mea­surement IC. The CDB5490U evaluation board operates from a single USB or 5V power supply. An op­tional 3.3V power supply input is available for powering the CS5490 directly. The evaluation board
interfaces the CS5490 to a PC via a USB cable. To accomplish this, the board comes equipped with a
C8051F342 microcontroller and a USB interface. Additionally, the CDB5490U GUI software provides
easy access to the internal registers of the CS5490. The software provides a means to display the on-chip
ADC performance in the time domain or frequency domain.

1.2 Evaluation Board Overview

The board is partitioned into two main sections: analog and digital. The analog section consists of the
CS5490, passive anti-aliasing filters, and a high-voltage section with an attenuation resistor network. The
digital section consists of the C8051F342 microcontroller, LCD, test switches, reset circuitry, and USB in­terface. The board also has a user-friendly power supply connection. The assembly information and de­fault configurations for jumpers are shown below.

DS923DB5 5

CDB5490U



O VIN-

O O VIN-

GND

VIN-

(Default)



O VIN+
O O VIN+
O O VIN+

GND

Line

VIN+

(Default)



O VIN-
O O VIN-

GND

VIN-



O VIN+
O O VIN+
O O VIN+

GND

Line

VIN+



O VIN-
O O VIN-

GND

VIN-



O VIN+
O O VIN+
O O VIN+

GND

Line

VIN+



O VIN-
O O VIN-

GND

VIN-



O VIN+
O O VIN+
O O VIN+

GND

Line

VIN+

VIN+

VIN-

250 mVp

CDB5490U

CS5490

J3

J6

J11

C4

0.027UF

C9

0.027UF

R6

1K

R7

1K

J45

VIN+

VIN-

Figure 2. Voltage Channel — Low-voltage Input

1.3 Analog Section

The analog section of the CDB5490U is highly configurable. Onboard signal conditioning options for the
voltage and current channels enable most applications to interface directly to the sensors. The following
two sections define the voltage and current channel configurations.

1.3.1 Voltage Sensor Connection

There are three input signal options for the voltage channel input (VIN±): an external low-voltage signal
(via screw terminals or XLR connections), high-voltage line inputs, or GND. Figure 1 illustrates the options
available.

Table 1. Voltage Channel Input Signal Selection

INPUT Description J11 J6

Selects External

VIN±

VIN±

Low-voltage Fully
Differential Signal

Selects External
Low-voltage Sin­gle-ended Signal

GND

High-Voltage

Line

Selects Grounding

the Input

Selects External

High-voltage AC

Line Signal

The CDB5490U evaluation board provides screw-type terminals (J3) or XLR connectors (J30) to connect
low-voltage input signals to the voltage channel (see Figure 2). The screw terminals are labeled as
VIN+ / VIN-. An R-C network at the channel input provides a simple, configurable anti-alias filter. By in­stalling jumpers on J6 to position VIN+ and J11 to position VIN-, the input voltage signal is supplied from
the screw terminals or XLR connections.

The CDB5490U evaluation board provides screw-type terminals (J4) to connect a high-voltage line input.
By installing jumpers on J6 to position LINE and J11 to position GND, the input voltage signal is supplied
from the high-voltage input. Extreme care should be used when connecting high-voltage signals to the
CDB5490U evaluation board (see Figure 3).

6 DS923DB5

CDB5490U

GND

LINE

CS5490

CDB5490U

NEUTRAL

LINE

J4

J11

J6

R5
1K

C9

0.027UF

C4

0.027UF

R7

1K

R6

1K

R8

422K

R12

422K

R14

422K

R15

422K

J45

VIN-

VIN+

Figure 3. Voltage Channel — High-voltage Input

1k

4 422k1k+

----------------------------------------

1

1689

-------------

=

300V r m s

250mVp

2

-----------------------

1689=

The default attenuation network provides the following attenuation:

With the CS5490 input range of 250mVp at maximum AC line input of:

is acceptable. It is recommended to apply a 10% margin for the AC line input (270Vrms).

The CDB5490U evaluation board provides input shorting options for calibration and noise performance
measurements. With a jumper on J6 and J11 in the GND position, the inputs are connected to analog
ground (GND).

DS923DB5 7

CDB5490U



O IIN+

O O IIN+

IIN+

GND

(Default)



O IIN-

O O IIN-

GND

IIN-

(Default)



O IIN+

O O IIN+

IIN+

GND



O IIN-

O O IIN-

GND

IIN-



O IIN+

O O IIN+

IIN+

GND



O IIN-

O O IIN-

GND

IIN-

IIN-

IIN+

GND

GND

CS5490

CDB5490U

250 mVp

J1

J7

J8

C5

0.033UF

C6

0.033UF

R11

NO POP

R1

100

R2
100

R9

NO POP

R13

NO POP

R49 1K

R50 1K

C34

0.033UF

C35

0.033UF

J44

J46

R51

0

J53/J56

J54

IIN+

IIN-

Figure 4. Current Channel — Low-voltage Input

1.3.2 Current Sensor Connection

Current input options include an external signal (via screw terminals or XLR connectors) or GND. Table 2
illustrates the options available.

Table 2. Current Channel Input Signal Selection

INPUT Description J8 J7

Selects External

IIN±

IIN±

Low-voltage,

Fully Differential

Signal

Selects External

Low-voltage,

Single-ended

Signal

GND

Selects Grounding

the Input

There are two input signal options for the current channel (IIN±). The CDB5490U evaluation board pro­vides screw-type terminals (J1) or XLR connectors (J28) to connect an input signal to the current channel.
The screw terminals are labeled as IIN+ / IIN-. An R-C network at the channel input provides a simple,
configurable anti-alias filter (see Figure 4).

By installing jumpers on J8 to position IIN+, J7 to position IIN-, the input current signal is supplied from
the screw terminals or XLR connectors.

The CDB5490U evaluation board provides input shorting options for calibration and noise performance
measurements. With a jumper on J8 and J7 in the GND position, the inputs are connected to analog
ground (GND).

8 DS923DB5

CDB5490U

Figure 5. MCU Connection Window

J18 J20 J50

UART

via MCU

Ƒ OPTO
ż RX
ż DIGITAL
(default)

Ƒ OPTO
ż TX
ż DIGITAL
(default)

Ƒ VDDA
ż EN2
ż GND
(default)

Low speed

UART

Ƒ OPTO
ż RX
ż DIGITAL

Ƒ OPTO
ż TX
ż DIGITAL

Ƒ VDDA
ż EN2
ż GND

1.4 Digital Section

The digital section contains the microcontroller, USB interface, LCD, optical isolation, JTAG header, reset
circuitry, and external interface headers (J17 and J19). The microcontroller interfaces the UART of the
CS5490 with the USB connection to the PC, enabling the GUI software to access all of the CS5490 reg­isters and functions.

1.4.1 Serial Port Selection

Communication to the CS5490 is provided through a standard UART. It is necessary to establish commu­nication with the MCU before serial port communication with the CS5490 (see Figure 5).

The CDB5490U board provides two UART communication options - normal speed and low speed. Table 3
provides the serial communication options for the UART.

Table 3. Serial Communication Options

DS923DB5 9

CDB5490U

1.4.2 Interface to Microcontroller

Interface headers J17 and J19 are provided to allow the CDB5490U to be connected to an external energy
registration device or an external microcontroller. Interface header J17 provides direct access to the
CS5490 pins while interface header J19 provides an isolated connection. It is imperative to use the iso­lated connection (J19) when high-voltage signals are used. Failure to use isolation can result in damage
to components or electrical shock. Refer to section 1.4.3 Digital Isolation for details on signal isolation.

Interface header J19 can be used to connect to the external microcontroller. To connect the CS5490 to
an external microcontroller, R37, R42, and R43 must be removed from the board.

1.4.3 Digital Isolation

Two types of isolation are provided: a low-speed optical coupler and high-speed digital isolation for UART
communication. Default jumper settings provide high-speed digital isolators. To enable high-speed digital
isolators, place jumpers (J18 and J20) in the RX-to-DIGITAL position and TX-to-DIGITAL position. To en­able the high-speed digital isolators, it is also necessary to install jumper (J50) in the VDDA position. To
enable the low-speed optical UART communication, place jumpers (J18 and J20) in the RX-to-OPTICAL
position and TX-to-OPTICAL position.

The high-speed digital isolators operate from DC to 150Mbps. The low-speed optical couplers operate to
a maximum speed of about 4.8kHz. All the signals supplied to the isolators are available to the MCU.

1.4.4 Additional Device Pin Access

The CS5490's digital output pin (DO) is routed to a LED, which provides a simple visual check of the digital
output. Jumper J39 is equipped at the factory to enable the LED. The DO digital output pin is supplied to
the digital isolation using jumper J49.

The MODE pin jumper (J15) should be installed in the VDDA to MODE position.

The CS5490 system clock can be connected to an onboard quartz crystal, or an external clock can be
supplied to the CS5490 XIN pin though jumper J48. To connect the onboard quartz crystal, install jumper
J43 in the XIN to CRYSTAL position. To connect XIN to an external clock, install jumper J43 in the XIN to
XIN_EXT position.

10 DS923DB5

CDB5490U

6XSSO\
6RXUFH

&6



6RXUFH



%LQGLQJ

SRVW

J36&J37

86%

6XSSO\

J24

9

7HUPLQDOV

J27

9''$

J21 J38

9B

J26

86%

On-board

3.

3 V

Regulator

NC +5V NC

Ƒ

VDDA

ż

VDDA

(default)

Ƒ

+3.3V

ż

VDDA

ż

+3.3V_2

(default)

Ƒ

+5V EXT

ż

+5V

ż

+5V USB

(default)

([WHUQDO9



86%

Binding

Post

+3.3 V +5V NC

Ƒ

VDDA

ż

VDDA

Ƒ

+3.3V

ż

VDDA

ż

+3.3V_2

Ƒ

+5V EXT

ż

+5V

ż

+5V USB

([WHUQDO9

On-board

3.3V

regulator

NC NC +5V

Ƒ

VDDA

ż

VDDA

Ƒ

+3.3V

ż

VDDA

ż

+3.3V_2

Ƒ

+5V EXT

ż

+5V

ż

+5V USB

1.5 Power Supply Section

Table 4 illustrates the power supply connections on the evaluation board. The positive analog (VDDA) for
the CS5490 can be supplied using the +3.3V binding post (J36 and J37) or the onboard +3.3V regulator.
Jumper J38 allows the VDDA supply to be sourced from the +3.3V binding post (J37) or the regulated
+3.3V supply. The DC-DC converter (U8) powers the onboard +3.3V regulator. Jumper J26 allows the
+5V supply to be sourced from either the +5V EXT screw connector (J27) or the +5V USB supply. The
+5V supplies the power for the microcontroller (8051_REGIN) and the DC-DC converter (U8). Jumper J21
is used to measure the CS5490 analog supply current and must be installed.

When connecting the CDB5490U board to the AC line through non-isolated sensors, it is strongly recom­mended that the CS5490 GND reference is connected to the neutral, the non-isolated current sensor is
connected on neutral, and the CS5490 is supplied by +3.3V isolated from AC line. The DC-DC converter
(U8) provides 1kVDC isolation, while no isolation is provided for the 3.3V binding post connections. If
+3.3V is used from the binding post, then the external 3.3VDC power supply must be isolated from the
AC line. To prevent electric shock and damages, always use an isolated power source.

Table 4. Power Supply Selection

DS923DB5 11

CDB5490U

IIN-

IIN+

GND

GND

GND

LINE

CS5490

CDB5490U

PHASE

NEUTRAL

J1

J4

J7

J8

J11

J6

R5
1K

C5

0.033UF

C6

0.033UF

C9

0.027UF

C4

0.027UF

R11

NO POP

R1

100

R2

100

R7

1K

R6

1K

R9

NO POP

R13

NO POP

R8

422K

R12

422K

R14

422K

R15

422K

R49 1K

R50 1K

C34

0.033UF

C35

0.033UF

J44

J46

R51

0

J45

J53

J54

SHUN T

IIN+

IIN-

VIN-

VIN+

Figure 6. Shunt Sensor Power Meter

1.6 Typical Sensor Connections

The CDB5490U evaluation board provides connections directly to several types of sensors. Flexible on­board filter networks provide a convenient configuration for three common transducers: current shunt, cur­rent transformer (CT), or Rogowski coil.

1.6.1 Shunt Power Meter Example

An inexpensive current shunt configuration is easily achievable with the CDB5490U evaluation board.
Figure 6 depicts the voltage and current connections for a shunt sensor and its associated filter configu­rations.

It is strongly recommended that a low-side (neutral path) current shunt is used — especially in high-volt­age situations. Make sure that all signals are well connected before the power source is turned on. Ex­treme care should be taken when connecting high-voltage signals to the CDB5490U evaluation board.

In this configuration it is unnecessary to use a burden resistor. A single anti-alias filter is all that is required
for the current channel. Below the filter corner frequency, the CS5490 inputs will see the same voltage
that is across the shunt. Therefore the shunt voltage should be kept below the maximum of 50mVp with
I-Channel PGA = 50x. A 10% margin is recommended for the shunt voltage (45mVp).

12 DS923DB5

CDB5490U

V

burdenIburdenRburden



I

primary

N

------------------------

R

burden

==

IIN-

IIN+

GND

GND

GND

LINE

CS5490

CDB5490U

PHASE

NEUTRAL

J1

J4

J7

J8

J11

J6

R5
1K

C5

0.033UF

C6

0.033UF

C9

0.027UF

C4

0.027UF

R11

2.2

R1

100

R2

100

R7

1K

R6

1K

R9

1K

R13

1K

R8

422K

R12

422K

R14

422K

R15

422K

R49 1K

R50 1K

C34

0.033UF

C35

0.033UF

J44

J46

R51

0

J45

J53

J54

IIN+

IIN-

VIN-

VIN+

Figure 7. Current Transformer Power Meter

1.6.2 Current Transformer Power Meter Example

A slightly more expensive option is to use a current transformer (CT) to connect the AC current to the
CDB5490U evaluation board. Figure 7 depicts the voltage and current connections for a CT sensor and
its associated filter configurations.

NEVER “open circuit” a CT. Make sure that all signals are well connected before the power source is
turned on. Extreme care should be taken when connecting high-voltage signals to the CDB5490U evalu­ation board.

The burden resistor (R11) is necessary in a CT application to convert the secondary current into voltage.
Knowledge of the current transformer turns ratio (N) is key to determining the proper CS5490 input voltage
(V

) that the meter places on the system. The optimum secondary voltage (V

burden

current input should be 10% less than the maximum channel voltage of 250mVp with I-channel
PGA = 10x. The secondary voltage (V
ondary current. Then the secondary current (I

) is determined by converting the primary current to the sec-

burden

) can be converted into a voltage by Ohm's Law.

burden

) at the maximum

burden

The secondary voltage (V

) is sourced to the CS5490 through a simple low-pass, anti-alias filter, and

burden

this voltage should not exceed the 250mVp.

DS923DB5 13

CDB5490U

IIN-

IIN+

GND

GND

GND

LINE

CS5490

CDB5490U

PHASE

NEUTRAL

J1

J4

J7

J8

J11

J6

R5
1K

C5

0.033UF

C6

0.033UF

C9

0.027UF

C4

0.027UF

R11

NO POP

R1

100

R2

100

R7

1K

R6

1K

R9

NO POP

R13

NO POP

R8

422K

R12

422K

R14

422K

R15

422K

R49 1K

R50 1K

C34

0.033UF

C35

0.033UF

J44

J46

R51

0

J45

J53

J54

IIN+

IIN-

VIN-

VIN+

Figure 8. Rogowski Coil Power Meter

1.6.3 Rogowski Coil Power Meter Example

Rogowski coil power meter can be easily connected to the CDB5490U evaluation board. Figure 8 shows
the voltage and current connections for the Rogowski sensor and its associated filter configurations.

For more information, see AN365: Using the CS5480/84/90 Energy Measurement IC with Rogowski Coil
Current Sensors.

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