LD3985M33R from STMicroelectronics, in a SOT-23-5L. 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	VI	power_in	Input voltage of the LDO. Operating range 2.5 V to 6 V (absolute max -0.3 to 6 V; withstands 6.5 V non-repetitive spike for 200 ms). Decouple with 1 µF ceramic capacitor to GND.
2	GND	power_in	Common ground reference for the regulator.
3	VINH	input	Inhibit (enable) input. ON mode when VINH >= 1.2 V, OFF mode when VINH <= 0.4 V. Absolute max -0.3 V to VI+0.3 V. Input leakage ±1 nA typ. Must not be left floating (no internal pull-up/pull-down).
4	BYPASS	passive	Reference bypass pin. Connect an external capacitor (typically 10 nF) to GND to filter internal reference noise and minimize output noise voltage (30 µVRMS over 10 Hz-100 kHz).
5	VO	power_out	Regulated output voltage of the LDO (3.3 V nominal for the M33 option). Delivers up to 150 mA guaranteed (300 mA min peak, 550 mA typ). Requires a low-ESR ceramic output capacitor (Co >= 1 µF, ESR 5 mΩ-5 Ω).

Key specifications

Parameter	Value
Manufacturer	STMicroelectronics
Package	SOT-23-5L
Category	PMIC
Pins	5

Ordering variants

Same part, different packaging or reel option.

LD3985M33RM
LD3985M33RMTR
LD3985M33RXX
LD3985M33RXXTR
LD3985M33RJ

CAD (KiCad official)

Symbol: LD3985M33R
Footprint: Package_TO_SOT_SMD:SOT-23-5
3D model: SOT-23-5L (KiCad packages3D, STEP)

3D model downloads

Two STEP files. Same geometry, different body top:

File	Size	Use it when
`ld3985m33r.step`	85 KB	You want the bare part, or you mark your own boards.
`ld3985m33r-etched.step`	2.4 MB	You want the part with `LD3985M33R` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 557 faces against 102 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 (22 pp, sha256 c78962c126412ffb, 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