Compared with diode-ORing, mosfet-based solutions have a lower voltage drop, but need a control chip to shut the mosfet off against reverse flow should an input power supply fail short circuit.

"State-of-the-art power supplies respond very quickly, but fail very quickly," Picor business development manager Carl Smith told Electronics Weekly. "Our ORing solutions detect in 160ns, faster than competing solutions, and have a higher mosfet discharge current."

In the family there are three bipolar control chips for use with external n-channel mosfets: PI2001 for single-mosfet positive rail high-side switching, PI2002 for back-to-back mosfet pair positive rail switching where complete load disconnect is required under fault conditions, and the PI203 for single-mosfet negative rail low-side switching.

All offer 4A of mosfet gate discharge current to switch the transistor off in a few tens of nanoseconds.
Single mosfet types shut down reverse current; and via a lag pin indicate faults including: reverse current, over and under voltage, over temperature and excessive forward current. The dual mosfet chip flags and shuts down all conditions.

All come in 3x3mm TDFN and 5x6mm SOIC packages.

The integrated mosfet versions have similar functions and all come in 5x7x2mm packages.

Single internal mosfet high-side versions include an 8V 24A 1.5mΩ mosfet variant and a 30V 12A 5.5mΩ variant.

Devices have a 'slave' pin to allow paralleling.

All high-side switching versions need an auxiliary power supply of between 4.5 and 13.2V with respect to the rail they are switching. "We are going to be coming out with some products with integrated charge pumps," said Smith.

See http://www.vicorpower.com/picorpower/