The LT4250L/LT4250H is a negative 48V hot swap controller that allows a board to be safely inserted and removed from a live backplane. By controlling the gate voltage of an external N-channel pass transistor, inrush current is limited to a programmable value. If the input voltage is less than the programmable undervoltage threshold or greater than the overvoltage threshold, the pass transistor is turned off. A programmable current limit protects the system against shorts. After a 500µs timeout, the current limit activates the electronic circuit breaker. The PWRGD (LT4250L) or PWRGD (LT4250H) signal can be used to directly enable a power module. The LT4250L is designed for modules with a low enable input and the LT4250H for modules with a high enable input. The LT4250L/LT4250H are available in 8-pin PDIP and SO packages.
The LT4250L and LT4250H are 8‑pin negative‑48 V hot‑swap controllers that enable safe board insertion and removal from a live backplane. They limit inrush current, provide programmable over‑voltage, under‑voltage lockout, and a current‑limit that trips an electronic circuit breaker after 500 µs.
The devices include a Power‑Good (PWRGD) output, sense and gate pins for external MOSFET control, and are available in PDIP and SO packages. Typical applications include hot‑swap board insertion, power‑supply ramping, and EMI‑filter integration.
| Supply Voltage Operating Range | 20 V – 80 V |
|---|---|
| Supply Current (UV=3 V, OV=Vpp, SENSE=Vpp) | 1.6 mA – 5 mA |
| Undervoltage Lockout Threshold | 15.4 V |
| Current Limit Trip Voltage | 40 mV – 60 mV |
If the current limit remains active for over 500 µs, the electronic circuit breaker trips, pulling the GATE pin low and turning off the external MOSFET.