Datasheet CT1815FP, CT1815 Datasheet (ACT)

eroflex Circuit T

– Data Bus Modules For The Future © SCDCT1815 REV A 6/12/98

www.aeroflex.com

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CT1815

10MHz Low Level Serial Interface

for MIL-STD-1397 Type D

Features

• Internally set threshold

• Matched to 50 ohm system impedance power on and off

• Operates with ±5 volt supplies

• Power management

• Accepts synchronous input data

• Unique Manchester decoder requires no clock

• Generates one clock per received bit

• May be used for serial decoding of indefinite word lengths

• Other Wire and Fiber Optic types available

General Description

The CT1815 is a single hybrid micro-circuit which incorporates a serial encoder, transceiver, and Manchester decoder
in one package. The encoder accepts serial NRZ data in conjunction with two synchronous clocks. This data stream is
then Manchester encoded and maybe transformer coupled thru an external transformer to a 75 ohm tri-axial cable for
transmission through up to 1000 feet of cable. The CT1815 receiver section accepts bipolar Manchester encoded
signals and passes level detected signals to the serial decoder. The serial decoder reconstructs an NRZ data stream
with derived clock. This allows the data to be processed by our CT2500 monolithic protocol chip for MIL-STD-1397 serial
interfaces. All the input and output signals of the CT1815 are completely compatible with the CT2500. The CT1815 has
a power management function. A transmitter standby mode is available to reduce the overall power consumption of the
CT1815. Aeroflex Circuit Technology is an 80,000ft

2

MIL-PRF-38534 certified facility in Plainview, N.Y.

CIRCUIT TECHNOLOGY

ISO

900

I

1

Serial NRZ Data

10 MHz Shift Clock

20 MHz Gated Clock

Envelope

Master Reset

Encoder Enable

Power Management

Decoded Data Envelope

Clock Regeneration

Clock

R

Decoded Data

Serial

Manchester

Encoder

Power

Management

Manchester

Decoder

and

R

Data

Reconstruction

Figure 1 – Block Diagram

XFMR SEC/DATA Input

XFMR SEC

Primary

+5V

1CT:1

ACT15-1031

XFMR SEC/DATA

Rx Strobe

Data

Output

Primary

Data

Output

XFMR SEC

External to

Hybrid

78Ω

Input

echnology

Transmission

The CT1815 accepts synchronous NRZ Data in
conjunction with two clocks signals. The NRZ data
stream is then converted to Manchester code which
is transformer coupled to a 75 ohm Tri-axial cable for
transmission up to 1000 ft.

The transmitter may be placed into standby
condition. This reduces power consumption by
approximately 600mW. Power management is made
available via two standard TTL input pins. The
Receiver is always active and is not affected by the
power management circuitry.

The transceiver is matched for 75 ohm operation
over a wide band of frequencies. This condition is
maintained with power on and off.

Reception

The CT1815 receiver section accepts a bipolar
signal which is level detected and passed to the
serial decoder. The decoder section reconstructs
the data and strips the clock from the serial stream.
An NRZ decoded data stream is then produced

Encoder Timing / Transmitter Specification

synchronously with a recovered clock. The receiver
is designed to meet the MIL-STD-1397 Type D
requirements.

Electrical Requirements

The specification detailed herein encompasses a
hybrid Transceiver/Encoder-Decoder designed to
meet the requirements of the MIL-STD-1397 Type D.

The transceiver is transformer coupled to the
specified triaxial cable and is screened to the
individual test methods of MIL-STD-883

See Figure 1 for Block Diagram. Inputs and
Outputs are all Synchronous NRZ DATA STREAMS

Transformer Isolation

The CT1815 is connected with pin 3 and pin 32 to
the ACT15-1031 transformer secondary winding.
The center tap of the secondary winding is
connected to +5 volts. For matching 75Ω load
operation, a 78Ω resistor must be placed across the
primary winding of the transformer.

Symbol Parameter / Condition Min Typ Max Unit

Encode Timing

t1 Input data set-up time
t2 Encode clock set-up time
t3 Encode envelope set-up time
t4 Encode envelope turn-off time
t5 Transmitter activation set-up time
t6 Transmitter deactivation hold-time
tw1 20 MHz gated CK pulse width high
tw2 Encoder shift CK pulse width high

Output Signals

Va Output amplitude (see Figure 2)
T Pulse period
Ts Width of 1st positive half bit
Te Width of last half bit
T/2 Half pulse period
Tr Pulse rise time
Tf Pulse fall time
Vs Voltage overshoot
Tos Offset Voltage 2T after last zero crossing
Tdtx Delay from 20 MHz clock input to data output on

transformer secondary

Zo Output Impedance

10 40 ns
10 40 ns
10 40 ns
10 35 ns

150 ns

50 ns
20 30 ns
45 55 ns

2.75 3.25 3.75 V
97 100 103 ns
45 65 ns
47 65 ns
47 50 53 ns

2.0 V/ns

2.0 V/ns
350 mV
150 mV

20 55 ns

70 75 80 Ω

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P1 = 50ns ±0.1%
P2 = 100ns ±0.1%

NRZ

BIT NBIT 2BIT 1BIT 0

t

1

Serial Input

t

Encoder

t

2

W2

Shift Clock Input

P2

t

20 MHz

W1

GATED Clock

P1

t

4

NRZ

t

3

Envelope

t

Encoder Enable

5

t

6

Power Management

Pin

T

f

2T

Transmitter

Output

T

dTX

V

a

V

S

V

US

90%

10%

90%

10%

T

T

OS

T/2

T

r

T

Figure 2 Encoder – Transmitter Timing

T

e

Manchester II

Receiver Data

1st Data

BIT

2nd Data

BIT

3rd Data

BIT

4th Data

BIT

5th Data

BIT

Decoded

Data

Envelope

R

Data

X

Data

CK

t

1

t

7

R

R

t

2

t

3

t

4

t

5

t

6

t

5

Figure 3 Receiver / Decode Timing

Symbol Parameter / Condition Min Nom Max Units

t1 Envelope delay time - 45 100 nsec
t2 Data decode delay - 115 125 nsec
t3 Clock low transition delay - 130 - nsec
t4 Clock
t5 Clock

high time 35 50 65 nsec

R

low time 35 50 65 nsec

R

t6 Envelope off delay 120 - 270 nsec
t7 Receiver strobe enable to input data set-up time 5 - - nsec
t8 Receiver strobe disable to input data hold-time 20 - - ?

Power Management Functional Table

Encoder

Enable

(Pin 10)

Power Management

Input

(Pin 9)

Receiver

Status

0 0 Active Standby
X 1 Active Active
1 X Active Active

Power management timing see Figure 2.

Transmitter

Status

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Functional Description and Pinout

Pin

Pin Name Function

#

Load or

Drive

1 No connection
2 No connection
3 XFMR secondary/

Transmitter-receiver I/O pin

RX data input
4 Test Point No connection permitted
5 Test Point No connection permitted
6 Test Point No connection permitted
7 -5 Volts
8 R
9 Power management

strobe Low level disables receiver 3 S loads

X

Controls transmitter power consumption in conjunction with pin 10 1 S load

input

10 Encoder enable Controls transmitter power consumption in conjunction with pin 9 1 S load
11 Case/signal GND
12 Case/signal GND
13 Decoded data

envelope

High after reception of first half bit; goes low after reception of last
half bit (normally low in inactive state)

4 S drive

14 TP3 test point Alignment point: no electrical connection permitted
15 TP1 test point Alignment point: no electrical connection permitted
16 TP2 test point Alignment point: no electrical connection permitted
17 -5 Volts
18 TP4 test point Alignment point: no electrical connection permitted
19 Clock

R

Reconstructed clock; one clock pulse per input bit received 3 S drive
20 No connection
21 Decoded Data

R

NRZ reconstructed data. Sampled on clockR rising edge 3 S drive
22 No connection
23 +5 volts
24 +5 volts
25 10 MHz encoder shift

One cycle required per data bit. Must be high in first half of bit cell 1 S load

clock
26 NRZ serial input data Serial input to be Manchester encoded with the 20 MHz gated CK 1 S load
27 Encode envelope Must be high to enable transmission; must go low before reception

1 S load

of last 20 MHz positive edge to complete transmission

28 20 MHz gated clock

(encoder)

Each bit to be encoded requires two positive edges of the 20 MHz
CK. These edges must occur at 25ns and 75ns into the bit cell.

1 S load

The end of transmission requires an additional edge in conjunction

29 Master reset

with a logic low on the encode envelope. t
Logic low resets encoder 2 S load

, tF < 5nsec.

R

reset pulse <15 nsec
30 No connection
31 No connection
32 XFMR secondary/

RX DATA
33 XFMR
34 XFMR

TX DATA

input
secondary Secondary isolated winding, same phase as outer conducter
primary/

output

Transmitter-Receiver I/O pin

Transformer lead for connection to outer conductor of tri-axial

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Load and Drive Definitions

1 S load: requires

= -2mA max., VIL = 0.8V max

I

IL

= 50µA max., VIH = 2.5V min CIN < 15 pf

I

IH

1 S drive:

= 50µA min., VOH = 2.5V min

I

OH

= -2 mA min., VOL = 0.5V max

I

OL

Power Consumption

Current (mA)

Typ Max

Standby mode 235 305

I

CC

Standby mode 75 100

I

EE

100% Transmission 447 585

I

CC

100% Transmission 242 315

I

EE

Absolute Maximum Ratings

V

(Pins 23, 24) +7 Volts Max

CC

(Pins 7, 17) -7 Volts Max

V

EE

Logic Input Voltage Applied:

Logic Low -1.2V @ 10mA Max
Logic High +5.5 Volts

Damage will not result from cable open circuits or
short circuits (on the transformer primary) of the
following types:

• Line-to-line

• Line-to-ground

• 120V AC 60Hz common mode signal

Environmental Parameters

Operating Temperature -55°C to +100°C Case
Storage Temperature -55°C to +150°C
Screened per individual test methods of

MIL-STD-883.

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CIRCUIT TECHNOLOGY

Plainview New York 11830

Toll Free Inquiries: 1-(800)THE-1553

Ordering Information

Model Number Package

CT1815
CT1815FP

Plug-In Package Outline

Pin 1 & ESD
Designator

.270 ±.010

.100 ±.005

TYP

Flat Package Outline

.015 ±.003 .100 ±.005

1.810
MAX

.018 ±.002

(17 Pins/Side)

DIA

.200

.120 ±.010

Both Sides

Plug-in Package

Flat Package

1.200 ±.005

.100 TYP

Both Sides

.180 MAX

.400 MIN

1.410
MAX

Lead 1 & ESD
Designator

1.810
MAX

Aeroflex Circuit Technology
35 South Service Road

Specifications subject to change without notice.

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Telephone: [phone]

FAX: [phone]

.010 ±.002