Linear Technology's LTC4231 is a micropower Hot Swap controller that allows safe circuit board insertion and removal from a live power supply. An internal high-side switch driver controls the gate of an external N-channel MOSFET. Back-to-back MOSFETs can be used for reverse supply protection down to -40 V. The LTC4231 provides a debounce delay and allows the GATE to be ramped up at an adjustable rate. After startup, the LTC4231's quiescent current drops to 4 μA during normal operation with output active. UVL, UVH, OV and GNDSW monitor overvoltage and undervoltage periodically, keeping total quiescent current low. Pulling SHDN low shuts down the LTC4231 and quiescent current drops to 0.3 μA. During an overcurrent fault, the LTC4231 actively limits current while running an adjustable timer. The LTC4231-1 remains off after a current fault while the LTC4231-2 automatically reapplies power after a cool-down period.