# SM18C

**MDD Microdiode Semiconductor** · ESD And Surge Protection (TVS/ESD) · SOT-23

SM18C from MDD Microdiode Semiconductor, in a SOT-23. 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 | I/O1 | passive | Protected line 1, a bidirectional TVS channel to pin 3, with VRWM 18 V and breakdown voltage 20.0 V min at 1 mA for SM18C. |
| 2 | I/O2 | passive | Protected line 2, a bidirectional TVS channel to pin 3, with VRWM 18 V and breakdown voltage 20.0 V min at 1 mA for SM18C. |
| 3 | COMMON | passive | Common node of both bidirectional TVS diodes, the shared return for pins 1 and 2 (±30 kV IEC 61000-4-2 air and contact). |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | MDD Microdiode Semiconductor |
| Package | SOT-23 |
| Category | Circuit Protection |
| Pins | 3 |

## CAD (KiCad official)

- Symbol: `SM18C`
- Footprint: `Package_TO_SOT_SMD:SOT-23`
- 3D model: SOT-23 (KiCad packages3D, STEP)
- 3D model files: `sm18c-etched.step` / `sm18c-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `sm18c.step` / `sm18c.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [MDD Microdiode Semiconductor datasheet](https://jlcpcb.com/api/file/downloadByFileSystemAccessId/8590234724930121728) (5 pp, sha256 `deddb74e0c252eba`, retrieved 2026-10-09, 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/sm18c-datasheet.pdf)