The STMicroelectronics ST1PS02B1QTR is a synchronous step-down (buck) DC-DC converter in a tiny 12-TQFN package measuring 1.7x2 mm.
The output is adjustable from 1.8 V up to 2.5 V, which matches the core voltage of many low-power MCUs, FPGAs, and wireless SoCs. Because the output is adjustable via an external resistor divider, you can dial in intermediate voltages like 2.0 V or 2.2 V without changing the part.
400 mA output and synchronous rectification
Rated for 400 mA continuous output, this converter can power a small sensor node, a Bluetooth LE module, or a low-power MCU plus its peripherals.
Housed in a 12-UFQFN (also specified as 12-TQFN 1.7x2 mm), this is a very small package for a 400 mA regulator. The datasheet layout recommendation should be followed closely — the small pitch makes hand-soldering difficult, so reflow assembly is the intended method.