Supertex HV300 and HV310, hot-swappable controllers, control the negative supply, when plugged into the power supply to connect to a live backplane card or module. They can be used with conventional "negative 48V" or higher voltages to power system buses up to negative 90V. Prevents spin glitches during initial power-up operation, (typically found and after the load capacitance is fully charged in the input filter of the DC-DC converter) HV300 (and HV310) problems, a power good signal. This signal is usually used to enable DC-DC conversion. The only difference between the HV300 and HV310 is the polarity of the PWRGD signal lines to accommodate different DC-DC converter models. Once the PWRGD signal has been established the device sleeps in a low power state, important for large systems or modules with many single hot-swappable cards. The pass element is required by the external power MOSFET, plus a ramp capacitor and resistor to establish current limit and undervoltage lockout. There is no need for additional external buffer components. Programmable function, over-voltage and under-voltage detection, the load connection of the input voltage locks out if the bus (input) voltage is out of range. An internal voltage regulator creates a stable reference and maintains accurate gate drive voltages. Provides unique control loop scheme for full current control and limiting during start-up.

The initial external N-channel MOSFET is the gate signal off, preventing input glitches. After a delay (while the internal circuitry is activated) the inrush current to the load is limited to the gated output. current may rise and be limited to a maximum value set by an external resistor. The initial delay time to allow contact bounce, charging operation is performed by a single external ramp capacitor connected to the RAMP pin. When the load capacitor is fully charged, the controller enters current limit mode, more time delay occurs before the pass transistor of the external N-channel MOSFET switches to full conduction, and the PWRGD output signal is activated. The controller will then transition to a low-power standby mode.