The LT ®1640AL/LT1640AH are 8-pin, negative voltage Hot Swap TM controllers that allow a board to be safely inserted and removed from a live backplane
The LT1640AL and LT1640AH are 8‑pin negative‑voltage hot‑swap controllers that enable safe insertion and removal of boards from a live –48 V backplane. They limit inrush current, provide programmable over‑ and undervoltage protection, and include a programmable electronic circuit breaker.
Key features include programmable inrush current control, power‑good output (PWRGD), analog OV and UV inputs for over‑ and undervoltage detection, and a sense pin for circuit‑breaker trip detection. Typical applications are central‑office switching, distributed –48 V power systems, and negative power‑supply control.
The OV pin is the analog over‑voltage input; when it exceeds the 1.223 V low‑to‑high threshold it pulls the GATE pin low to protect the circuit.
Inrush current is limited by programming the gate voltage of an external N‑channel pass transistor, which controls the current when the board is inserted into a live backplane.
The PWRGD pin toggles when the input voltage is within the power‑good threshold, providing a power‑good output that can directly enable a power module.