# LM431ASF

**HTC Korea TAEJIN Tech** · Voltage Regulators - Linear, Low Drop Out (LDO) Regulators · SOT-23

LM431ASF from HTC Korea TAEJIN Tech, in a SOT-23. Pinout and pin descriptions extracted from the manufacturer datasheet (extract_pins, cross-checked by a second model); symbol, footprint, and 3D from KiCad-official CAD.

## Pinout

| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | CATHODE | passive | Cathode of the shunt regulator, which the datasheet's pin table labels as input supply voltage; recommended cathode voltage is VREF to 40 V, recommended cathode current is 0.5 to 100 mA, and absolute maximum cathode voltage is 42 V. |
| 2 | ANODE | power_in | Anode, which the datasheet's pin table labels as ground; the reference is taken relative to this pin. |
| 3 | REFERENCE | input | Reference voltage input, 2.475 to 2.525 V for the LM431A at VKA = VREF and IK = 10 mA, with reference input current range of -0.05 to 10 mA (absolute maximum). |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | HTC Korea TAEJIN Tech |
| Package | SOT-23 |
| Category | Power Management (PMIC) |
| Pins | 3 |

## Electrical characteristics

Limits as printed in the datasheet (page.json `metadata.characteristics` carries them as data).

| Parameter | Symbol | Min | Typ | Max | Unit | Conditions | Page |
|---|---|---|---|---|---|---|---|
| Reference Input Voltage (LM431A) | VREF | 2.475 | 2.5 | 2.525 | V | VKA=VREF, IK=10mA | 4 |
| Deviation of Reference Input Voltage | ΔVREF/ΔT |  | 15 | 30 | mV | VKA=VREF, IK=10mA, TA=Full Range | 4 |
| Ratio of Change in Reference Input Voltage to Change in Cathode Voltage | ΔVREF/ΔVKA |  | -1.4 | -2.7 | mV/V | IK=10mA, ΔVKA=10V to VREF | 4 |
| Ratio of Change in Reference Input Voltage to Change in Cathode Voltage | ΔVREF/ΔVKA |  | -1 | -2 | mV/V | IK=10mA, ΔVKA=36V to 10V | 4 |
| Reference Input Current | IREF |  | 1.8 | 4 | µA | IKA=10mA, R1=10kΩ, R2=∞ | 4 |
| Deviation of Reference Input Current | ΔIREF/ΔT |  | 0.4 | 1.2 | µA | IK=10mA, R1=10kΩ, R2=∞, TA=Full Range | 4 |
| Minimum Cathode Current for Regulation | IK(MIN) |  |  | 0.5 | mA | VKA=VREF | 4 |
| Off-State Cathode Current | IK(OFF) |  | 0.17 | 0.9 | µA | VKA=36V, VREF=0 | 4 |
| Dynamic Impedance | ZKA |  | 0.27 | 0.5 | Ω | VKA=VREF, IK=1mA~100mA, f≤1kHz | 4 |
| Cathode Voltage (recommended) | VKA |  |  | 40 | V |  | 2 |
| Cathode Current (recommended) | IKA | 0.5 |  | 100 | mA |  | 2 |
| Operating Temperature Range | TOPR | -40 |  | 125 | °C |  | 2 |
| Cathode Voltage (absolute maximum) | VKA |  |  | 42 | V |  | 1 |
| Cathode Current Range | IKA | -100 |  | 150 | mA |  | 1 |
| Reference Input Current Range | IREF | -0.05 |  | 10 | mA |  | 1 |
| Junction Temperature Range | TJ | -40 |  | 150 | °C |  | 1 |
| Storage Temperature Range | TSTG | -65 |  | 150 | °C |  | 1 |

## CAD (KiCad official)

- Symbol: `LM431ASF`
- Footprint: `Package_TO_SOT_SMD:SOT-23`
- 3D model: SOT-23 (KiCad packages3D, STEP)
- 3D model files: `lm431asf-etched.step` / `lm431asf-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `lm431asf.step` / `lm431asf.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [HTC Korea TAEJIN Tech datasheet](https://jlcpcb.com/api/file/downloadByFileSystemAccessId/8603086281265979392) (11 pp, sha256 `17dd2d49771567a3`, retrieved 2026-10-18, tier: lcsc)
- **Extractor:** parts-factory `2.0.0` / `extract_pins 0.3`, primary `claude-haiku-5-5` (text), consensus `claude-sonnet-5-5` (agreed), guards: pin_guards 0.1: passed. Pins are checked against the footprint pad set and their cited datasheet pages before publish.
- **CAD:** KiCad official libraries (CC-BY-SA 4.0).

[Datasheet PDF](docs/lm431asf-datasheet.pdf)