Broadcom Inc. Optically Coupled 20 mA Current Loop Transmitter HCPL-4100

The HCPL-4100 isolated 20 mA currrent loop transmitter is designed to operate as a transmitter 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 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 integrated 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 degradation. The internal shield allows a guaranteed 1000 V/ms common mode transient immunity.

Logic Output Optocouplers 20mA Current Loop

OPTOCOUPLER, TRANSISTOR, 3.75KV, DIP-8; No. of Channels:1 Channel; Optocoupler Case Style:DIP; No. of Pins:8Pins; Forward Current If Max:-; Isolation Voltage:3.75kV; CTR Min:-; Collector Emitter Voltage V(br)ceo:27V; Product Range:- RoHS Compliant: No