Negative-rail hot swap for -48V telecom backplanes
The MAX5901LBEUT is a single-channel hot swap controller from Maxim's Simple Swapper™ family, designed to manage inrush current and protect downstream circuitry when boards are inserted into a live backplane. Its supply range of -9V to -100V targets the -48V telecom rack standard, where a hot-swap controller must handle the full -36V to -72V nominal swing plus transients. The internal switch handles the pass element, so no external MOSFET is needed for the basic function — the part integrates the N-channel FET on-chip.
Programmable protection and fault handling
Programmable features include circuit breaker threshold, current limit, slew rate, UVLO, and fault timeout — the designer sets the inrush profile and overcurrent trip point with external resistors and a capacitor. On a fault, the part can be configured for auto-retry or latched shutdown, and a thermal-limit circuit protects the die if the junction temperature climbs during a sustained overcurrent event. Supply current is 500 µA typical, a low overhead for the -48V rail where the controller's own draw is negligible compared to the load.
Active lifecycle and compliance note
Note that this part is marked RoHS non-compliant — the lead-bearing finish is intentional for applications where tin-whisker risk is unacceptable, such as high-reliability telecom or aerospace assemblies.