The LTC4261/LTC4261-2 negative voltage Hot SwapTM controllers allow a board to be safely inserted and removed from a live backplane. Using an external N-channel pass transistor, the board supply voltage can be ramped at an adjustable rate. The devices feature independently adjustable inrush current and overcurrent limits to minimize stresses on the pass transistor during start-up, input step and output short conditions. The LTC4261 defaults to latch-off while the LTC4261-2 defaults to auto-retry on overcurrent faults. An I2C interface and onboard 10-bit ADC allow monitoring of board current, voltage and fault status. A single-wire broadcast mode is available to simplify the interface by eliminating two optoisolators. The controllers have additional features to interrupt the host when a fault has occurred, notify when output power is good, detect insertion of a board and turn off the pass transistor if an external supply monitor fails to indicate power good within a timeout period.