The LT4239 hot swap controller allows a board to be safely inserted and removed from a live backplane. Using external N-channel pass transistors, board supply voltage and inrush current are ramped up at a controlled rate. Dual 12V gate drive supports high current loads by providing a two-stage start-up that first charges the load capacitance followed by enabling a low on-resistance path to the load. The supply output is protected against short-circuit faults with a fast-acting electronic circuit breaker.By placing the sense resistor on the output side and an RC filter at the device’s supply pin, the MOSFET avalanching can suppress the surge voltage when it is abruptly turned off without the additional TVS at the board supply input.The LT4239 features a current monitor that amplifies the voltage across an external sense resistor. It also provides undervoltage protection, and reports fault and power good status for the supply. A boost mode allows the circuit breaker and current limit thresholds to be raised to ride through load surges without generating a fault.APPLICATIONSElectronic Circuit BreakerEnterprise Servers and Data Storage SystemsNetwork Routers and Switches