# SZ1SMA18AT3G

**Littelfuse** · ESD And Surge Protection (TVS/ESD) · SMA

SZ1SMA18AT3G from Littelfuse, in a SMA. 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 terminal, identified by the polarity band on the package; this is the cathode of the uni-directional TVS diode. |
| 2 | ANODE | passive | Anode terminal of the uni-directional TVS diode, which clamps transients to the device's working peak reverse voltage and clamping limits. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | Littelfuse |
| Package | SMA |
| 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 | 20 | 21.05 | 22.1 | V | @ IT = 1 mA (Note 7) | 3 |
| Maximum reverse leakage current | IR |  |  | 2.5 | µA | @ VRWM | 3 |
| Forward voltage | VF |  |  | 3.5 | V | @ IF = 30 A, for all types | 2 |
| Peak power dissipation | PPK |  |  | 400 | W | @ TL = 25°C, pulse width = 1 ms (Note 1) | 1 |
| DC power dissipation | PD |  |  | 1 | W | @ TL = 75°C, measured zero lead length (Note 2) | 1 |
| DC power dissipation | PD |  |  | 0.5 | W | @ TA = 25°C (Note 3) | 1 |
| Forward surge current | IFSM |  |  | 40 | A | @ TA = 25°C, 1/2 sine wave, PW = 8.3 ms (Note 4) | 1 |
| Operating and storage temperature range | TJ, Tstg | -65 |  | 150 | °C |  | 1 |
| Maximum reverse peak pulse current | IPP |  |  | 13.7 | A | Column value for this MPN (VC test current) | 3 |
| Clamping voltage | VC |  | 29.2 |  | V | @ IPP = 13.7 A | 3 |
| Working peak reverse voltage | VRWM |  | 18 |  | V | Note 6 | 3 |
| Typical junction capacitance | C |  | 645 |  | pF | Bias voltage = 0 V, F = 1.0 MHz, TJ = 25°C (Note 9) | 3 |
| Thermal resistance junction to lead | RθJL |  | 50 |  | °C/W | Measured zero lead length (Note 2) | 1 |
| Thermal resistance junction to ambient | RθJA |  | 250 |  | °C/W | FR-4 board, minimum recommended footprint (Note 3) | 1 |
| Derating above 75°C (lead) | PD |  | 20 |  | mW/°C | Derate above TL = 75°C | 1 |
| Derating above 25°C (ambient) | PD |  | 4 |  | mW/°C | Derate above TA = 25°C | 1 |

## CAD (KiCad official)

- Symbol: `SZ1SMA18AT3G`
- Footprint: `Diode_SMD:D_SMA`
- 3D model: SMA (KiCad packages3D, STEP)
- 3D model files: `sz1sma18at3g-etched.step` / `sz1sma18at3g-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `sz1sma18at3g.step` / `sz1sma18at3g.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/8588938348836622336) (5 pp, sha256 `0efc269c31859c3d`, retrieved 2026-10-16, 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/sz1sma18at3g-datasheet.pdf)