Power Sequencing Device Lets Boards Be Swapped Safely

Providing board-level hot-swap power sequencing, soft turn-on, rapid turn-off and current limiting, the UCC3991 device allows safe insertion and extraction of boards from a powered backplane connector. Two channels are provided for controlling two independent positive supply voltages ranging from 3V to 12V. A third output is also included for activating a power switch for a negative supply.Power sequencing is accomplished by using long and short pins in the board connector to initiate a well-defined turn-on when connected and early power-fail detection and rapid power-down when disconnected. The full-featured 24-pin version is for PCI applications; an 18-pin version eliminates additional status bits and enable functions.