# TL431U

**CBI** · Voltage References · SOT-89-3

TL431U from CBI, 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 | REFERENCE | input | Reference input that the internal amplifier regulates to Vref of 2.5 V (2.475-2.525 V at IKA = 10 mA), with reference input current of 1.5 µA typ and 4 µA max. |
| 2 | ANODE | passive | Anode terminal, the return path for the cathode current; minimum cathode current for regulation is 0.45 mA typ and 1.0 mA max. |
| 3 | CATHODE | passive | Cathode terminal, rated for a cathode voltage of 37 V maximum and a continuous cathode current range of -100 to +150 mA. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | CBI |
| Package | SOT-89-3 |
| Category | Power Management ICs |
| 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 |
|---|---|---|---|---|---|---|---|
| Cathode Voltage | VKA |  |  | 37 | V |  | 1 |
| Cathode Current Range (Continuous) | IKA | -100 |  | 150 | mA |  | 1 |
| Reference Input Current Range | Iref | 0.05 |  | 10 | mA |  | 1 |
| Power Dissipation | PD |  |  | 500 | mW |  | 1 |
| Operating Ambient Temperature Range | Topr | -25 |  | 85 | ℃ | Operating temperature range applies unless otherwise specified | 1 |
| Storage Temperature Range | Tstg | -65 |  | 150 | ℃ |  | 1 |
| Reference input voltage | Vref | 2.475 | 2.5 | 2.525 | V | VKA=VREF, IKA=10mA; Ta=25℃ | 1 |
| Deviation of reference input voltage over temperature (note) | △Vref /T |  | 4.5 | 17 | mV | △VKA=VREF, IKA=10mA; TMIN≤Ta≤TMAX | 1 |
| Ratio of change in reference input voltage to change in cathode voltage (10V to VREF) | △Vref /△VKA |  | -1 | -2.7 | mV/V | △VKA=10V~VREF | 1 |
| Ratio of change in reference input voltage to change in cathode voltage (36V to 10V) | △Vref /△VKA |  | -0.5 | -2 | mV/V | IKA=10mA; △VKA=36V~10V | 1 |
| Reference input current | Iref |  | 1.5 | 4 | μA | IKA=10mA, R1=10kΩ, R2=∞ | 1 |
| Deviation of reference input current over full temperature range | △Iref /T |  | 0.4 | 1.2 | μA | IKA=10mA, R1=10kΩ, R2=∞ | 1 |
| Minimum cathode current for regulation | IKA(min) |  | 0.45 | 1 | mA | VKA=VREF | 1 |
| Off-state cathode current | IKA(OFF) |  | 0.05 | 1 | μA | VKA=36V, VREF=0 | 1 |
| Dynamic impedance | ZKA |  | 0.15 | 0.5 | Ω | VKA=VREF, IKA=1 to 100mA, f≤1.0kHz | 1 |
| Operating Junction Temperature | Tj |  |  | 150 | ℃ |  | 1 |
| Thermal Resistance from Junction to Ambient | RθJA |  | 250 |  | ℃/W |  | 1 |

## CAD (KiCad official)

- Symbol: `TL431U`
- Footprint: `Package_TO_SOT_SMD:SOT-89-3`
- 3D model: SOT-89-3 (KiCad packages3D, STEP)
- 3D model files: `tl431u-etched.step` / `tl431u-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `tl431u.step` / `tl431u.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [CBI datasheet](docs/tl431u-datasheet.pdf) (4 pp, sha256 `ad1604d4033d3f79`, retrieved 2026-11-05, 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/tl431u-datasheet.pdf)