The MAX5911/MAX5912 are fully integrated hot-swap switches for negative supply rails. These devices allow the safe insertion and removal of circuit cards into live backplanes or ports without causing problematic glitches on the negative power-supply rail. They also monitor various circuit parameters and disconnect the load if a fault condition occurs, alerting the host with a logic-level FAULT output. The MAX5911/MAX5912 operate over a voltage range of -16V to -65V and are designed to permit hot plugging of an IP phone into a hub, but are not limited to that operation. During startup, an internal power FET regulates the current between the backplane power source and the load to 280mA for MAX5911 and 415mA for MAX5912. After startup, the FET is fully enhanced to reduce its on-resistance. To ensure robust operation, the MAX5911/ MAX5912 contain built-in safety features that prevent damage to the internal FET. They include an enable input, which responds to positive logic signals (+3.3V or +5V), allowing the host system to disconnect the load. ENABLE is also used to reset the device after a latching fault condition occurs.