HV312

The HV302 and HV312 Hotswap Controllers perform current limiting, circuit breaker protection, over and under voltage detection power management functions during insertion of cards or modules into live backplanes and connectors. They may be used in systems where active control is implemented in the negative lead of supplies ranging from -10V to -90V or +10V to +90V.

During initial power application the external pass device HV312 is held off by a "normally-on" circuit that clamps its gate low. Thereafter UV/OV and power-on-reset work together to suppress gate turn on due to contact bounce. When stable connection has been established for the duration of a programmed time delay, the inrush current is controlled and limited to a programmed level using one of two possible methods; servo mode or drain to ramp feedback capacitor mode. When charging of the load capacitor is completed, the open drain PWRGD-A flag is asserted. Open drain PWRGD-B, PWRGD-C and PWRGD-D flags are asserted sequentially after the expiration of their respective programmed time delays. Thereafter HV312 transitions to a low power sleep mode and continues to monitor current and input voltage. If full charging of the load capacitor is not achieved within 100ms or the circuit breaker is tripped at any time, the external pass device is turned off and all four PWRGD flags are reset to the inactive state. Thereafter a programmable auto-retry timer will hold the pass device off to allow it to cool before resetting and initiating auto-retry. The auto-retry can be disabled using a single resistor if desired.