Fixed 2.2 V output — no divider resistors needed
The 1.25 MHz switching frequency lets you use a small inductor — typically 2.2 µH — which keeps the total solution footprint tight on a SOT-23-5 Thin board.
400 mA at 1.25 MHz — inductor sizing and ripple
At 400 mA output, the 1.25 MHz switching rate keeps the inductor ripple current around 120 mA peak-to-peak with a 2.2 µH inductor. That ripple is low enough that output capacitors in the 10 µF range give you under 20 mV ripple at the load — fine for powering a sensor or a small MCU rail. The synchronous rectifier means no external Schottky catch diode, which saves a component and a placement step. The internal low-side FET handles the freewheeling current, so the only external parts are the input cap, output cap, and inductor.
SOT-23-5 Thin — rework and layout notes
The SOT-23-5 Thin (TSOT-23-5) package is a 5-pin body about 2.9 mm × 1.6 mm. The thin profile means the thermal pad area on the PCB is small — the junction-to-ambient thermal resistance is around 250 °C/W, so at 400 mA the die temperature stays well under the 85 °C limit in most indoor environments. Hand-soldering is straightforward: tack the centre tab first, then the pins.