BROADCOM HCPL-4200

The HCPL-4200 is an optically coupled Current Loop Receiver designed to operate as a receiver in equipment using the 20mA current loop. The current loop systems conventionally signal a logic high state by transmitting 20mA of loop current (MARK) and signal a logic low state by allowing no more than a few milli-amperes of loop current. Optical coupling of the signal from the current loop to the logic output breaks ground loops and provides for a very high common mode rejection. The buffer circuit on its current loop side provides typically 0.8mA of hysteresis which increases the immunity to common mode and differential mode noise. The buffer also provides a controlled amount of LED drive current which takes into account any LED light output degradation. The internal shield allows a guaranteed 1000V/ms common mode transient immunity.