400 mA step-down in a 1.7x2 mm TQFN
The ST1PS02C1QTR is a synchronous buck regulator from STMicroelectronics that delivers up to 400 mA from a 1.8 V to 5.5 V input rail. It switches at 2 MHz, which keeps the external inductor and capacitors small enough to fit a tight layout. The output is adjustable between 2.6 V and 3.3 V, making it a direct fit for powering 2.8 V or 3.3 V sensor rails, wireless modules, or MCU core supplies in battery-powered or portable designs. The part comes in a 12-TQFN package measuring 1.7x2 mm, so board area is the primary constraint this part solves.
Switching frequency and inductor sizing
The 2 MHz switching frequency pushes the fundamental and its harmonics above the AM broadcast band, which simplifies EMI filtering in noise-sensitive analog front-ends. The trade-off is higher switching losses than a 500 kHz part, but at 400 mA output the efficiency curve still peaks above 90% in the mid-load range.
Input and output voltage boundaries
The input range spans 1.8 V to 5.5 V, so it can run from a single Li-ion cell (3.0 V to 4.2 V), two alkaline cells (2.4 V to 3.0 V), or a regulated 3.3 V or 5 V rail. The minimum input of 1.8 V means it will operate deep into battery discharge for a single-cell Li-ion, but not from a near-dead alkaline pair below 1.8 V. If your load needs exactly 3.3 V, the 3.3 V maximum output is the ceiling — no headroom for a 3.6 V or 5 V rail.
It is not qualified for under-hood automotive (no AEC-Q100 claim in the listing) or extended-temperature downhole or avionics applications.
It is ROHS3 compliant. If you are qualifying a new design, this part has no imminent obsolescence risk, but always check the ST product page for PCN notifications before committing a long production run.