This design note describes ways to drive an optocoupler. One of the most popular is to use a TL431 Adjustable-Shunt Regulator. However a regulator-control lC-such as the UC3832 UC3833 or UC3836 substituted for the TL43431-provides numerous additional features besides regulating the output. Overcurrent limiting and fault-protection handshaking with external control logic and the introduction of