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.
100 ns off-delay — what it means for 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.
Temperature grade and environment
Rated for -40°C to 85°C ambient, the part covers outdoor telecom cabinets, industrial base-station shelters, and factory-floor redundant supplies. No AEC-Q100 listing here, so it is not qualified for under-hood automotive — keep it in the controlled-climate rack.
Lifecycle and sourcing
No official second-source alternate is listed in the available documentation, so dual-sourcing would require a separate qualification of a functionally equivalent ORing controller from another vendor.