DC1926A: Dual Ideal Bridge Controller

Demonstration circuit 1926A features the LTC4353, a dual low voltage ideal diode controller, in a typical 12A application. The LTC4353 creates two near-ideal diodes using external N-channel MOSFETs thereby replacing high power Schottky diodes and their associated heat sinks. Ideal diodes enable low loss power ORing and supply holdup applications.

The LTC®4353 controls external N-channel MOSFETs to implement an ideal diode function. It replaces two high power Schottky diodes and their associated heat sinks, saving power and board area. The ideal diode function permits low loss power supply ORing and supply holdup applications.

The LTC4353 regulates the forward-voltage drop across the MOSFET to ensure smooth current transfer in diode-OR applications. A fast turn-on reduces the load voltage droop during supply switchover. If the input supply fails or is shorted, a fast turn-off minimizes reverse-current transients.

The controller operates with supplies from 2.9V to 18V. If both supplies are below 2.9V, an external supply is needed at the VCC pin. Enable inputs can be used to turn off the MOSFET and put the controller in a low current state. Status outputs indicate whether the MOSFETs are on or off.