The S39421 is a fully integrated hot swap controller intended for use on add-in cards that may be inserted into or removed from powered-on host platforms. The S39421 performs a variety of tasks starting with the validation of proper card insertion and the presence of "in-spec" voltages at the host platform interface. Once power is switched on, the S39421 continues to monitor the back-end power to the add-in card and the host power supply. If either the 5V or 3.3V supplies drop below Vtrip the S39421 will immediately assert the RESET outputs and power-down the add-in card. In addition to the power control for the add-in card, the S39421 provides status signals that can be employed by the host and for the control of bus interface components.