Synchronous buck controller for 4V to 38V rails
The LTC3851IUD#PBF from Analog Devices is a single-phase synchronous step-down switching regulator controller. It drives external N-channel MOSFETs to deliver a regulated positive output from input rails spanning 4V to 38V, making it suitable for intermediate bus conversion in industrial, telecom, and automotive power systems. The controller operates with a programmable switching frequency from 250kHz to 750kHz, letting the designer trade inductor size against switching losses. The 99% maximum duty cycle allows the output to stay in regulation through input voltage dips nearly down to the output voltage, useful for hold-up or battery-backed designs. Control features include current limit, enable input, frequency control via an external resistor, programmable soft start, and output tracking for supply sequencing. The part is rated for junction temperatures from -40°C to 125°C, covering industrial and under-hood automotive environments.
Package and footprint
Housed in a 16-lead WFQFN with exposed pad (3mm x 3mm body), the LTC3851IUD#PBF is a surface-mount device. The exposed pad must be soldered to a PCB thermal land and connected to the ground plane for adequate heat dissipation, especially at higher switching frequencies or elevated ambient temperatures. The supplier device package is 16-QFN (3x3).
Lifecycle and compliance
The LTC3851IUD#PBF is listed as Active in production status and is ROHS3 compliant.