LTC4251

LTC4251/LTC4251-1/ LTC4251-2 Negative Voltage Hot Swap Controllers in SOT-23 FEATURES n Allows Safe Board Insertion and Removal from a Live –48V Backplane n Floating Topology Permits Very High Voltage Operation n Programmable Analog Current Limit with Circuit Breaker Timer n Fast Response Time Limits Peak Fault Current n Programmable Timer n Programmable Undervoltage/Overvoltage Protection n Low Profile (1mm) ThinSOT™ Package APPLICATIONS n Hot Board Insertion n Electronic Circuit Breaker n –48V Distributed Power Systems n Negative Power Supply Control n Central Office Switching n Programmable Current Limiting Circuit n High Availability Servers n Disk Arrays DESCRIPTION The LTC®4251/LTC4251-1/LTC4251-2 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 LTC4251 UV/OV thresholds are designed to match the standard telecom operating range of – 43V to –75V. The LTC4251‑1 UV/OV threshold...