The LTC®3900 is a secondary-side synchronous rectifier driver designed to be used in isolated forward converter power supplies. The chip drives N-channel rectifier MOSFETs and accepts pulse sychronization from the primary-side controller via a pulse transformer. The LTC3900 incorporates a full range of protection for the external MOSFETs. A programmable timeout function is included that disables both drivers when the synchronization signal is missing or incorrect. Additionally, the chip senses the output inductor current through the drainsource resistance of the catch MOSFET, shutting off the MOSFET if the inductor current reverses. The LTC3900 also shuts off the drivers if the supply voltage is too low.
