# SMF4729A

**Changjing** · Zener Diodes · SOD-123FL

SMF4729A from Changjing, 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 | K | passive | Cathode, marked by the cathode bar on the package; zener voltage VZ for SMF4729A is 3.42V min / 3.47V max per the table at IZT=69mA (nominal 3.3V). |
| 2 | A | passive | Anode; forward voltage VF is max 1.5V at IF=200mA. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | Changjing |
| Package | SOD-123FL |
| Category | Diodes |
| 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 |
|---|---|---|---|---|---|---|---|
| Zener voltage (min/max) | VZ | 3.42 | 3.6 | 3.78 | V | @IZT = 69 mA | 2 |
| Zener voltage tolerance |  | -5 |  | 5 | % | standard tolerance on nominal zener voltage | 2 |
| Test current | IZT |  | 69 |  | mA |  | 2 |
| Maximum Zener impedance | ZZT |  |  | 10 | Ω | @IZT | 2 |
| Maximum Zener impedance (knee) | ZZK |  |  | 400 | Ω | @IZK = 1 mA | 2 |
| Reverse leakage current | IR |  |  | 100 | uA | @VR = 1 V | 2 |
| Maximum DC Zener current | IZM |  |  | 251 | mA |  | 2 |
| Maximum surge current | IRM |  |  | 1255 | mApk | non-repetitive 8.3ms pulse width square wave or equivalent sine-wave | 2 |
| Forward voltage | VF |  |  | 1.5 | V | IF=200mA | 1 |
| Thermal resistance junction to ambient | RθJA |  |  | 170 | ℃/W | Between junction to ambient | 1 |
| Thermal resistance junction to lead | RθJL |  |  | 26 | ℃/W | Between junction to lead | 1 |
| Power dissipation | Pd |  |  | 1 | W | TL=75℃ | 1 |
| Operation junction and storage temperature range | TJ,Tstg | -55 |  | 150 | ℃ |  | 1 |

## CAD (KiCad official)

- Symbol: `SMF4729A`
- Footprint: `Diode_SMD:D_SOD-123F`
- 3D model: SOD-123FL (KiCad packages3D, STEP)
- 3D model files: `smf4729a-etched.step` / `smf4729a-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `smf4729a.step` / `smf4729a.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [Changjing datasheet](docs/smf4729a-datasheet.pdf) (5 pp, sha256 `8f6e4acc3701b115`, 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/smf4729a-datasheet.pdf)