High power, -ve supply, ideal diode-OR controller stands 300V transients

March 18, 2016 // By Graham Prophet
LTC4371 is a rugged ideal diode-OR controller for dual-feed high power telecom and datacom boards. The LTC4371 provides seamless handoff between redundant power supplies, replacing power Schottky diodes and associated heat sinks with N-channel MOSFETs, significantly reducing power loss, voltage drop and solution size.

The controller is designed to withstand ±300V or higher voltage transients experienced during lightning induced surges, load switching or supply short-circuit, and is presented as the most rugged diode-OR solution available. A built-in shunt-regulated supply with 350 µA quiescent current and high impedance drain pins enables large value external resistors to safely limit device current during such high voltage transients. External transient voltage suppressors are eliminated, saving cost and board area.


The LTC4371 servos a 15 mV forward voltage drop across the ideal diode MOSFETs to minimise power dissipation in high current applications. The linear servo technique blocks DC reverse current while ensuring smooth current transfer during supply switchover. During an input supply short-circuit, transient reverse current is minimised by a 2A gate turn-off current. A strong 5 mA gate pull-up current ensures rapid turn-on of the MOSFET, enabling AC rectification applications. The large gate currents provide ample drive when multiple MOSFETs are paralleled in high current 50A and 100A applications. Operating voltage range extends into the hundreds of volts due to the internal shunt regulator, while a 4.5V minimum supply accommodates low voltage -5V and -12V ORing applications. Open-circuit failure of the MOSFET or a series fuse is detected and signalled by a fault status output.


Specified over the 0°C to 70°C commercial and -40°C to 85°C industrial temperature ranges, the LTC4371 is offered in 10-pin MSOP and 3 x 3 mm DFN plastic packages. Pricing starts at $2.50 (1000).


Linear Technology; www.linear.com/product/LTC4371