# MF-USML500

**BOURNS** · Resettable Fuses · 1210

MF-USML500 from BOURNS, in a 1210. 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 | 1 | passive | Terminal 1 of an unpolarised fuse; either orientation. |
| 2 | 2 | passive | Terminal 2 of an unpolarised fuse; either orientation. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | BOURNS |
| Package | 1210 |
| Category | Circuit Protection |
| Pins | 2 |

## Electrical characteristics

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

| Parameter | Symbol | Min | Typ | Max | Unit | Conditions | Page |
|---|---|---|---|---|---|---|---|
| Resistance | R | 0.001 |  | 0.012 | Ω | In still air at 23 °C (Rmin / R1max) | 1 |
| Maximum time to trip |  |  |  | 2 | s | At 25 A | 1 |
| Maximum interrupt current | Imax |  |  | 50 | A |  | 1 |
| Resistance change after passive aging | ΔR/R | -10 |  | 10 | % | +85 °C, 1000 hours (typical) | 1 |
| Resistance change after humidity aging | ΔR/R | -15 |  | 15 | % | +85 °C, 85 % R.H., 100 hours (typical) | 1 |
| Resistance change after thermal shock | ΔR/R | -30 |  | 30 | % | -40 °C to +85 °C, 20 times (typical) | 1 |
| Hold current | Ihold |  | 5 |  | A | at 23 °C | 1 |
| Trip current | Itrip |  | 10 |  | A | at 23 °C | 1 |
| Tripped power dissipation |  |  | 1.2 |  | W | at 23 °C | 1 |
| Operating temperature | TA | -40 |  | 85 | °C |  | 1 |
| Storage temperature before opening |  |  |  | 40 | °C | Before opening, 70 % RH max | 1 |

## CAD (KiCad official)

- Symbol: `MF-USML500`
- Footprint: `Fuse:Fuse_1210_3225Metric`
- 3D model: 1210 (KiCad packages3D, STEP)
- 3D model files: `mf-usml500-etched.step` / `mf-usml500-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `mf-usml500.step` / `mf-usml500.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [BOURNS datasheet](https://jlcpcb.com/api/file/downloadByFileSystemAccessId/8589906480217419776) (7 pp, sha256 `86b60882e1aa972e`, retrieved 2026-10-18, tier: lcsc)
- **Extractor:** parts-factory `2.0.0` / `extract_pins`, primary `two-terminal convention` (convention), consensus `off` (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/mf-usml500-datasheet.pdf)