KIA431AF-RTF from KEC Semicon, in a SOT-89-3. 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	REF	input	Reference input. High-impedance input to the internal error amplifier that is compared against the 2.495 V bandgap. Typically tied to the tap of an external R1/R2 divider from cathode to anode to program Vka = Vref x (1 + R1/R2) + Iref x R1. Input current 1.8 uA typ, 4.0 uA max at 25 C.
2	A	power_in	Anode. Common/ground-side terminal of the shunt regulator; the internal reference and error amp are referenced to this pin. For SOT-89 the heat sink tab is electrically common to pin 2 (Anode).
3	K	power_in	Cathode. Regulated shunt output; sinks current through an external series resistor from the supply to hold Vka at the programmed value. Absolute max Vka = 37 V; continuous cathode current range -100 to +150 mA; minimum cathode current for regulation 0.5 mA typ (1.0 mA max).

Key specifications

Parameter	Value
Manufacturer	KEC Semicon
Package	SOT-89-3
Category	PMIC
Pins	3

Ordering variants

Same part, different packaging or reel option.

KIA431AF-RTFF
KIA431AF-RTFZF
KIA431AF-RTF
KIA431AF-RTFBF
KIA431AF-RTF(blank)
KIA431AF-RTFZ
KIA431AF-RTFA
KIA431AF-RTFB
KIA431AF-RTFM
KIA431AF-RTFZM
KIA431AF-RTFAM
KIA431AF-RTFBM

CAD (KiCad official)

Symbol: KIA431AF-RTF
Footprint: Package_TO_SOT_SMD:SOT-89-3
3D model: SOT-89-3 (KiCad packages3D, STEP)

3D model downloads

Two STEP files. Same geometry, different body top:

File	Size	Use it when
`kia431af-rtf.step`	57 KB	You want the bare part, or you mark your own boards.
`kia431af-rtf-etched.step`	1.3 MB	You want the part with `KIA431AF-RTF` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 371 faces against 42 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: KEC Semicon datasheet (7 pp, sha256 b0b1ac14e62a5a3f, retrieved 2026-08-17, tier: lcsc)
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