LTC4252-1

` Allows Safe Board Insertion and Removal from a Live 48V Backplane
` Floating Topology Permits Very High Voltage Operation Programmable Analog Current Limit With Circuit Breaker Timer
` Fast Response Time Limits Peak Fault Current
` Programmable Soft-Start Current Limit
` Programmable Timer with Drain Voltage Accelerated Response
` Programmable Undervoltage/Overvoltage Protection
` LTC4252-1: Latch Off After Fault
` LTC4252-2: Automatic Retry After Fault

The LTC4252-1 negative voltage Hot Swap^TM controller llows a board to be safely inserted and removed from a ive backplane. Output current of LTC4252-1 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 of LTC4252-1 disconnect the load whenever the input supply exceeds the desired operating range. The LTC4252-1's supply input is shunt regulated, allowing safe operation with very high supply voltages. A multifunction timer delays initial startup and controls the circuit breaker's response time. The circuit breaker's response time is accelerated by sensing excessive MOSFET drain voltage, keeping the MOSFET within its safe operating area (SOA). A programmable soft-start circuit controls MOSFET inrush current at startup. A power good status output of LTC4252-1 can enable a power module at start-up or disable it if the circuit breaker trips.

The LTC4252-1 latches off after a circuit breaker fault times out. The LTC4252-2 provides automatic retry after a fault. The LTC4252 is available in either an 8-pin or 10-pin MSOP.