Three-rail buck for mixed-voltage boards
The TPS65251-3RHAT from Texas Instruments is a triple-output step-down (buck) regulator that takes a 4.5V to 18V input rail and delivers one 3A output and one 2A output, plus a third lower-current rail — all adjustable down to 0.8V. This is the kind of part you reach for when a single board needs 5V for logic, 3.3V for I/O, and 1.2V for a core, all from a common 12V or 5V supply bus. The synchronous rectifier keeps efficiency up, and the 300kHz to 2.2MHz switching range lets you pick between smaller inductors (higher frequency) and better efficiency (lower frequency).
The 3A and 2A outputs are the two you will size the magnetics for. The adjustable output range from 0.8V up to 17V covers most digital rails plus some analog supplies. At the top end, remember the 18V input max: if your input bus is 12V nominal, you have plenty of headroom; if you are running off a 16V rail, you are tight on margin.
Thermal and layout — the exposed pad is not optional
This comes in a 40-VFQFN with an exposed pad, 6x6 mm body. Surface-mount only — no socket, so plan for reflow or hot-air rework.