# TL431SQ

**PJSEMI** · Voltage Reference · SOT-89-3

TL431SQ from PJSEMI, in a SOT-89-3. 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 | REF | input | Reference input pin; reference input voltage is 2.495V typ (VKA=VREF, IKA=10mA) and reference input current range is -0.05 to +10mA. |
| 2 | ANODE | power_in | Anode pin, the most negative/ground-side terminal of the shunt reference. |
| 3 | CATHODE | passive | Cathode pin; cathode voltage up to 37V absolute max (VREF to 36V recommended) with sink current of 1 to 100mA. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | PJSEMI |
| Package | SOT-89-3 |
| 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 (TL431SQ) | VREF | 2.44 | 2.495 | 2.55 | V | VKA=VREF, IKA=10mA | 2 |
| Deviation of Reference Input Voltage Over Temperature | ∆VREF |  | 4.5 | 17 | mV | VKA=VREF, IKA=10mA, -40°C ≤TA≤+85°C | 2 |
| Ratio of Change in Reference Input Voltage to Change in Cathode Voltage | ∆VREF/∆VKA |  | -1 | -2.7 | mV/V | IKA=10mA, VKA=10V~VREF | 2 |
| Ratio of Change in Reference Input Voltage to Change in Cathode Voltage | ∆VREF/∆VKA |  | -0.5 | -2 | mV/V | IKA=10mA, VKA=36V~10V | 2 |
| Reference Input Current | IREF |  | 1.5 | 4 | µA | IKA=10mA, R1=10kΩ, R2=∞ | 2 |
| Deviation of Reference Input Current Over Full Temperature Range | ∆IREF |  | 0.4 | 1.2 | µA | IKA=10mA, R1=10kΩ, R2=∞, -25°C ≤TA≤+85°C | 2 |
| Minimum Cathode Current for Regulation | IKA(MIN) |  | 0.45 | 1 | mA | VKA=VREF | 2 |
| Off-State Cathode Current | IKA(OFF) |  | 0.05 | 1 | µA | VKA=36V, VREF=0 | 2 |
| Dynamic Impedance | ZKA |  | 0.15 | 0.5 | Ω | VKA=VREF, IKA=1~100mA, f≤1.0kHz | 2 |
| Cathode Voltage (recommended) | VKA |  |  | 36 | V |  | 1 |
| Cathode Current (recommended) | IKA | 1 |  | 100 | mA |  | 1 |
| Cathode Voltage (absolute maximum) | VKA |  |  | 37 | V | Ta=25℃ | 1 |
| Cathode Current Range (Continuous) | IKA | -100 |  | 150 | mA | Ta=25℃ | 1 |
| Reference Input Current Range | IREF | -0.05 |  | 10 | mA | Ta=25℃ | 1 |
| Power Dissipation | PD |  |  | 770 | mW | Ta=25℃ | 1 |
| Operating Junction Temperature | TJ |  |  | 150 | °C |  | 1 |
| Operating Ambient Temperature | TOPR | -40 |  | 85 | °C |  | 1 |
| Storage Temperature | TSTG | -65 |  | 150 | °C |  | 1 |

## CAD (KiCad official)

- Symbol: `TL431SQ`
- Footprint: `Package_TO_SOT_SMD:SOT-89-3`
- 3D model: SOT-89-3 (KiCad packages3D, STEP)
- 3D model files: `tl431sq-etched.step` / `tl431sq-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `tl431sq.step` / `tl431sq.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [PJSEMI datasheet](https://jlcpcb.com/api/file/downloadByFileSystemAccessId/8588886283062427649) (4 pp, sha256 `e6d5ebe44b99276e`, retrieved 2026-10-19, 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/tl431sq-datasheet.pdf)