The LTC4251B/LTC4251B-1/LTC4251B-2 negative voltage Hot Swap™controllers allow a board to be safely inserted and removed from a live backplane. Output current is controlled by three stages of current limiting: a timed circuit breaker, active current limiting and a fast feedforward path that limits peak current under worst-case catastrophic fault conditions.Programmable undervoltage and overvoltage detectors disconnect the load whenever the input supply exceeds the desired operating range. The supply input is shunt regulated, allowing safe operation with very high supply voltages. A multifunction timer delays initial start-up and controls the circuit breaker’s response time.The LTC4251B UV/OV thresholds are designed to match the standard telecom operating range of –43V to –75V. The LTC4251B-1 UV/OV thresholds extend the operating range to encompass –36V to –72V. The LTC4251B-2 implements a UV threshold of –43V only. The LTC4251B improves the ruggedness of the LTC4251 shunt regulator.UV/OVLTC4251–43V/–75VLTC4251-1–36V/–72VLTC4251-2–43V UV OnlyLTC4251B–43V/–75VLTC4251B-1–36V/–72VLTC4251B-2–43V UV OnlyApplicationsHot Board InsertionElectronic Circuit Breaker–48V Distributed Power SystemsNegative Power Supply ControlCentral Office SwitchingProgrammable Current Limiting CircuitHigh Availability ServersDisk Arrays