Three-phase synchronous buck controller for high-current POL rails
The LTC3773EUHF#PBF is a three-phase synchronous step-down (buck) switching regulator controller from Analog Devices, designed for high-current point-of-load (POL) regulation where multiple output phases share the load to reduce input ripple and spread thermal dissipation. Its 3.3 V to 36 V supply range covers common intermediate bus voltages (5 V, 12 V, 24 V) found in industrial and telecom systems, and the 98.5 % maximum duty cycle allows the output to run close to the input rail — useful when the input droops under load.
Switching frequency and control-loop flexibility
The switching frequency is programmable from 220 kHz to 560 kHz via an external resistor — a lower frequency reduces switching losses in the external MOSFETs, while a higher frequency shrinks the output inductor and capacitor footprint. Control features include Enable, Power Good, and Tracking, which allow sequencing of multiple rails during power-up and fault monitoring without external logic. Synchronous rectification is built in, meaning the controller drives both the high-side and low-side external N-channel MOSFETs — this eliminates the Schottky catch diode and improves efficiency above 90 % across most of the load range, though at the cost of needing a bootstrap diode and capacitor for the top gate drive.
Package and layout considerations for the 38-QFN
The tube packaging is typical for prototype and low-volume builds; for reflow assembly the part is also orderable in tape-and-reel under a different suffix.