# SMF4L28A

**Littelfuse** · TVS · SOD-123FL

SMF4L28A from Littelfuse, in a SOD-123FL. 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 | Cathode | passive | Cathode of the uni-directional TVS diode (marked by the color/cathode band), connected to the protected line, with VR 28 V stand-off, VBR 31.1-34.4 V at 1 mA and VC 45.4 V at 8.8 A Ipp. |
| 2 | Anode | passive | Anode of the uni-directional TVS diode, normally connected to ground/return, for 400 W peak pulse power at 10/1000µs. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | Littelfuse |
| Package | SOD-123FL |
| 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 |
|---|---|---|---|---|---|---|---|
| Breakdown Voltage | VBR | 31.1 |  | 34.4 | V | @ IT = 1 mA, uni-directional | 2 |
| Test Current | IT |  | 1 |  | mA | VBR measured after IT applied for 300µs | 2 |
| Reverse Stand-off Voltage | VR |  | 28 |  | V |  | 2 |
| Maximum Reverse Leakage | IR |  |  | 1 | µA | @ VR | 2 |
| Maximum Peak Pulse Current | Ipp |  |  | 8.8 | A | 10/1000µs exponential wave, derated per Fig.3 | 2 |
| Maximum Clamping Voltage | VC |  |  | 45.4 | V | @Ipp | 2 |
| Peak Pulse Power Dissipation 8/20µs | PPPM |  |  | 2000 | W | TA=25ºC, non-repetitive | 1 |
| Peak Pulse Power Dissipation 10/1000µs | PPPM |  |  | 400 | W | TA=25ºC, non-repetitive | 1 |
| Power Dissipation On Infinite Heat Sink | PD |  |  | 1 | W | TL=50ºC | 1 |
| Thermal Resistance Junction to Ambient | RƟJA |  | 220 |  | °C/W |  | 1 |
| Thermal Resistance Junction to Lead | RƟJL |  | 100 |  | °C/W |  | 1 |
| Operating and Storage Temperature Range | TJ,TSTG | -55 |  | 150 | °C |  | 1 |
| VBR Voltage Tolerance |  | -5 |  | 5 | % | 5% VBR Voltage Tolerance (A suffix) | 6 |

## 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 | • Matte tin lead-free plated • Halogen-free and RoHS | 1 |

## CAD (KiCad official)

- Symbol: `SMF4L28A`
- Footprint: `Diode_SMD:D_SOD-123F`
- 3D model: SOD-123FL (KiCad packages3D, STEP)
- 3D model files: `smf4l28a-etched.step` / `smf4l28a-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `smf4l28a.step` / `smf4l28a.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [Littelfuse datasheet](docs/smf4l28a-datasheet.pdf) (6 pp, sha256 `7971ab636790fc84`, retrieved 2026-10-22, tier: lcsc)
- **Extractor:** parts-factory `2.0.0` / `extract_pins 0.3`, primary `claude-sonnet-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/smf4l28a-datasheet.pdf)