What this ORing controller does on a redundant power rail
The Maxim Integrated MAX8555ETB+ is an N+1 ORing controller designed to drive an external N-Channel MOSFET as the pass element in redundant power-supply architectures. It handles the rail-ORing function without an internal switch — the FET is external, which lets you size the pass device for the load current. The part is aimed at redundant power supplies and telecom infrastructure where a single supply failure must not take down the bus.
When the input rail drops, the controller must turn off the external FET fast enough to prevent reverse current from the healthy rail back-feeding the failed one. The 100 ns off-delay is the propagation time from detecting the fault to the gate drive going low.
No AEC-Q100 listing here, so it is not qualified for under-hood automotive — keep it in the controlled-climate rack.