4 A synchronous buck in a 2×3 mm QFN
The Texas Instruments TPS621351RGXT is a 4 A synchronous step-down (buck) converter with an adjustable output from 0.8 V up to 12 V, supplied from a 3 V to 17 V input rail. It switches at 2.5 MHz, which keeps the inductor and output capacitors small — the whole supply fits in roughly the footprint of a postage stamp when you count the passives. The integrated synchronous rectifier means no external Schottky diode, saving one component and a bit of board area.