# UM1550S-33

**Union Semiconductor** · Voltage Regulators - Linear, Low Drop Out (LDO) Regulators · SOT23-3

UM1550S-33 from Union Semiconductor, in a SOT23-3. 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 | GND | power_in | Ground reference for the regulator. |
| 2 | VOUT | power_out | Regulated output voltage, 3.3V fixed for the -33 option, with 300mA guaranteed output current and a 350-550mA current limit. |
| 3 | VIN | power_in | Supply input accepting 1.8V to 8V (absolute maximum -0.3V to +10V). |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | Union Semiconductor |
| Package | SOT23-3 |
| Category | Power Management (PMIC) |
| Pins | 3 |

## CAD (KiCad official)

- Symbol: `UM1550S-33`
- Footprint: `Package_TO_SOT_SMD:SOT-23-3`
- 3D model: SOT23-3 (KiCad packages3D, STEP)
- 3D model files: `um1550s-33-etched.step` / `um1550s-33-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `um1550s-33.step` / `um1550s-33.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [Union Semiconductor datasheet](https://www.onsemi.com/pdf/datasheet/um1550s-33-d.pdf) (24 pp, sha256 `dbe4313ebf61b9cd`, retrieved 2026-10-27, tier: manufacturer)
- **Extractor:** parts-factory `2.0.0` / `extract_pins 0.3`, primary `claude-sonnet-5-5` (text+vision), consensus `claude-opus-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/um1550s-33-datasheet.pdf)