# 0438004.WR

**Littelfuse** · Disposable Fuses · 0603

0438004.WR from Littelfuse, in a 0603. 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 | Fuse terminal 1 (non-polarized, Ag/Ni/Sn termination); 4A rating (amp code 004.), 32V max voltage rating, 50A @ 32VDC/12VAC interrupting rating. |
| 2 | 2 | passive | Fuse terminal 2 (non-polarized, Ag/Ni/Sn termination); 4A rating (amp code 004.), 32V max voltage rating, 50A @ 32VDC/12VAC interrupting rating. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | Littelfuse |
| Package | 0603 |
| 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 |
|---|---|---|---|---|---|---|---|
| Opening time at 100% of ampere rating |  | 4 |  |  | Hours | 100% of ampere rating, at 25ºC | 1 |
| Opening time at 250% of ampere rating |  |  |  | 5 | Seconds | 250% of ampere rating, at 25ºC | 1 |
| Max. voltage rating |  |  |  | 32 | VDC | Amp code 004 (4 A) row | 1 |
| Interrupting rating |  |  |  | 50 | A | 50A @ 32VDC/12VAC, tested at rated voltage (note 1) | 1 |
| Operating temperature |  | -55 |  | 150 | ºC |  | 1 |
| Continuous operation current |  |  |  | 80 | % of rated current | Recommended for continuous operation | 1 |
| Nominal resistance |  |  | 0.017 |  | Ohms | Measured with <10% rated current | 1 |
| Nominal melting I2t |  |  | 0.692 |  | A2Sec. | Measured at 1 msec. opening time | 1 |
| Nominal voltage drop at rated current |  |  | 0.079 |  | V | Measured at rated current after temperature has stabilized | 1 |
| Nominal power dissipation at rated current |  |  | 0.316 |  | W | At rated current | 1 |

## Materials and finish

As the datasheet states them (page.json `metadata.appearance`; the 3D model's colours follow it).

| Part | Material | Colour / plating | Datasheet says | Page |
|---|---|---|---|---|
| contacts |  | tin | Terminations: Ag / Ni / Sn (100% Lead-free) Element Cover Coating: Lead-free Glass | 3 |

## CAD (KiCad official)

- Symbol: `0438004.WR`
- Footprint: `Fuse:Fuse_0603_1608Metric`
- 3D model: 0603 (KiCad packages3D, STEP)
- 3D model files: `0438004-wr-etched.step` / `0438004-wr-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `0438004-wr.step` / `0438004-wr.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [Littelfuse datasheet](https://jlcpcb.com/api/file/downloadByFileSystemAccessId/8588910161280831488) (3 pp, sha256 `a9efab228ef1992a`, retrieved 2026-10-18, tier: lcsc)
- **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/0438004-wr-datasheet.pdf)