Fixed 1.8V rail at 400 mA — the BOM-fit anchor
The TPS62222DDCR is a fixed 1.8V output, 400 mA step-down (buck) converter from Texas Instruments, switching at 1.25 MHz. The input range spans 2.5 V to 6 V, so it runs cleanly off a single-cell Li-ion (3.0–4.2 V) or a 3.3 V/5 V regulated rail.
SOT-23-Thin package — board area and reflow profile
Housed in a SOT-23-Thin (TSOT-23-5) package, the TPS62222DDCR occupies about 9 mm² of board area. The thin profile (nominal 1.0 mm height) fits into tight enclosures or behind a display bezel. Standard lead-free reflow profile applies; the part is rated MSL-1 per the TI datasheet, so no pre-bake is needed for reels stored dry. The five-pin layout — VIN, GND, EN, SW, FB — is the same as other TPS6222x fixed-output variants, so a single PCB footprint can serve multiple output voltages across the family.