Single-phase synchronous buck controller — 4V to 38V input range
The LTC3851EUD-1#PBF is a single-output, step-down (buck) switching regulator controller that drives external N-channel MOSFETs in a synchronous-rectifier topology. Its 4V to 38V supply range covers common industrial and intermediate bus rails without a pre-regulator. Switching frequency is programmable from 250kHz to 750kHz via a single resistor, letting the designer trade inductor size against efficiency. The 99% maximum duty cycle supports low-dropout operation near the input rail.
Package and thermal — 16-QFN with exposed pad
The exposed paddle is the primary thermal path and must be soldered to a copper area sized for the expected power dissipation. The ROHS3 compliance means no exemption-based lead in the solder finish.
Control features and output configuration
The controller integrates Enable, Frequency Control, Power Good, Soft Start, and Tracking. The Tracking pin allows the output to follow an external reference ramp during start-up, useful for sequencing multiple rails. Output configuration is positive, single-phase, with a transistor-drive output that directly drives the gates of external N-channel MOSFETs. The synchronous rectifier control outputs are complementary, preventing cross-conduction with proper dead-time selection.
ROHS3 compliant — suitable for EU markets without exemption paperwork.