What the LTC4371IMS#PBF does in a -48V backplane
The LTC4371IMS#PBF is an N+1 ORing controller designed for -48V distributed power systems and AdvancedTCA® equipment. It drives two external N-channel MOSFETs in a 2:1 input-to-output ratio — two incoming -48V feeds ORed onto a single output bus — so a fault on one feed doesn't drop the load. The controller itself draws 300 µA supply current, which keeps the quiescent overhead on the -48V rail negligible. That matters in telecom line cards where every milliwatt of housekeeping power is budgeted against the rectifier capacity. It operates from a 4.5V to 16V bias supply — not the -48V bus directly. The bias rail powers the gate drive for the external N-FETs, so a 12V auxiliary rail is the typical choice to get full gate enhancement.
External FETs and the BOM footprint
The LTC4371 has no internal switches — you supply the two N-channel MOSFETs. That means the BOM includes the controller plus a matched FET pair with Vds rating above the -48V rail (60V to 100V parts are common). FET selection sets the Rdson and the conduction loss, not the controller. The 10-MSOP package (3.00 mm width) fits on compact line-card layouts. The MSOP pitch is 0.50 mm — doable on a two-layer board with careful fan-out, though a four-layer stack with a dedicated ground plane lowers the noise coupling from the gate drive edges.
No need for the extended -55°C military range unless the equipment sits in an unheated enclosure at extreme altitude.
Lifecycle and compliance
ROHS3 compliant (lead-free).