Negative-rail hot swap for -48V telecom
The MAX5900LAEUT+ is a single-channel hot swap controller from the Simple Swapper™ family, designed to manage inrush current and protect downstream circuitry on negative supply rails ranging from -9V to -100V. Its primary application target is networking equipment, where -48V backplanes are standard; the controller sits between the input connector and the DC-DC converter, ramping the load capacitance up at a controlled slew rate to avoid glitching the shared bus.
Programmable protection and fault handling
The part integrates a programmable circuit breaker, current limit, and slew rate control, plus an undervoltage lockout (UVLO) threshold that can be set with external resistors. Fault behaviour is configurable between auto-retry and latched fault with a timeout — a choice that matters for remote equipment: auto-retry clears a transient overcurrent without a power cycle, while latched fault holds the output off until a supervisor intervenes, preventing repeated stress on the load. Supply current is 500 µA typical, low enough that the controller's own draw does not materially load the -48V rail in a multi-card chassis.
SOT-23-6 footprint and temperature grade
The controller does not contain an internal pass FET (Internal Switch(s): No), so an external N-channel MOSFET is required — the gate drive and fault sense are brought out to the drain and source pins.