Linear Technology's LTC4353 regulates the forward voltage drop across external N-channel MOSFETs to ensure smooth current transfer between supplies in diode-OR applications. In low voltage systems, a slow handoff between controllers results in a voltage droop during supply switchover. The fast <1 µs turn-on time of the LTC4353 ensures smooth switchover from one path to the other without oscillation. In the event the input supply fails or is shorted, a fast turn-off minimizes reverse current. In addition to redundant power supply ORing, the LTC4353 makes an excellent diode replacement in supply holdup applications where momentary collapse of supply voltage is isolated from the load.
The LTC4353 provides individual enable inputs that can be used to ensure priority to the main supply when supply voltages are within a MOSFET body diode drop of each other. With both enable inputs pulled low, the LTC4353 consumes just 75 µA per supply. Individual status outputs indicate whether the MOSFETs are on or off. The controller operates with supplies from 2.9 V to 18 V, and offers additional flexibility to control voltages down to 0 V by applying an external supply.