Optically Coupled 20 mA

Current Loop Transmitter

Technical Data

HCPL-4100

Features

• Guaranteed 20 mA Loop

Parameters

• Data Input Compatible with

LSTTL, TTL and CMOS

Logic

• Guaranteed Performance

over Temperature (0

70

• Internal Shield for High

Common Mode Rejection

• 20 kBaud Data Rate at 400

Metres Line Length

• Guaranteed On and Off

Output Current Levels

• Safety Approval

UL Recognized -2500 V rms for

1 minute

CSA Approved

• Optically Coupled 20 mA

Current Loop Receiver,

HCPL-4200, Also Available

Applications

• Isolated 20 mA Current

Loop Transmitter in:

Computer Peripherals

Industrial Control Equipment

Data Communications

Equipment

Description

The HCPL-4100 optocoupler is

designed to operate as a transmit-

ter in equipment using the 20 mA

current loop. 20 mA current loop

systems conventionally signal a

logic high state by transmitting

20 mA of loop current (MARK),

and signal a logic low state by

allowing no more than a few

milliamperes of loop current

(SPACE). Optical coupling of the

signal from the logic input to the

20 mA current loop breaks

ground loops and provides very

high immunity to common mode

interference.

The HCPL-4100 data input is

compatible with LSTTL, TTL, or

CMOS logic gates. The input

integrated circuit drives a GaAsP

LED. The light emitted by the

LED is sensed by a second inte-

grated circuit that allows 20 mA

to pass with a voltage drop of less

than 2.7 volts when no light is

emitted and allows less than 2 mA

to pass when light is emitted. The

transmitter output is capable of

withstanding 27 volts. The input

integrated circuit provides a

controlled amount of LED drive

current and takes into account

any LED light output degrada-

tion. The internal shield allows a

guaranteed 1000 V/

µs common

mode transient immunity.

CAUTION: It is advised that normal static precautions be taken in handling and assembly of this component to

prevent damage and/or degradation which may be induced by ESD.

Functional Diagram

A 0.1

µF bypass capacitor connected between pins 8 and 5 is recommended.