STM811SW16F from STMicroelectronics, in a SOT-143. Pinout and pin descriptions extracted from the manufacturer datasheet by ds2sf; symbol, footprint, and 3D from KiCad-official CAD.

Pinout

Pin	Name	Type	Function
1	VSS	power_in	Ground reference for the supervisor. Tie to the system ground plane.
2	RST	output	Active-low reset output (push-pull). Asserted (driven low) whenever VCC is below the reset threshold or MR is held low; remains asserted for at least trec (~140 ms) after the fault clears. Guaranteed valid down to VCC = 1 V; both sources and sinks current.
3	MR	input	Manual reset input, active low. A logic low asserts RST and keeps it asserted for trec after MR returns high. Internally pulled up to VCC via a 20 kΩ resistor, so it may be left open if unused; a normally-open push-button to GND provides a manual reset. Optional 0.1 µF cap from MR to GND for noise immunity.
4	VCC	power_in	Monitored supply voltage input (typ. 3.0/3.3/5 V depending on threshold variant). A 0.1 µF bypass capacitor to VSS mounted close to this pin is recommended for transient immunity.

Key specifications

Parameter	Value
Manufacturer	STMicroelectronics
Package	SOT-143
Category	PMIC
Pins	4

Ordering variants

Same part, different packaging or reel option.

STM811SW16F
STM812SW16F
STM811LW16F
STM811MW16F
STM811RW16F
STM811TW16F
STM809xW16F
STM810xW16F

CAD (KiCad official)

Symbol: STM811SW16F
Footprint: Package_TO_SOT_SMD:SOT-143
3D model: SOT-143 (KiCad packages3D, STEP)

3D model downloads

Two STEP files. Same geometry, different body top:

File	Size	Use it when
`stm811sw16f.step`	75 KB	You want the bare part, or you mark your own boards.
`stm811sw16f-etched.step`	1.9 MB	You want the part with `STM811SW16F` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 482 faces against 87 in the bare model. It survives export, section views, and rendering in any CAD tool, and it drops straight into KiCad or Fusion with no extra setup.

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

Datasheet: STMicroelectronics datasheet (21 pp, sha256 24f3f88facdeb210, retrieved 2026-08-17, tier: manufacturer)
Extractor: ds2sf (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF