# SZMMBZ5257BLT1G

**onsemi** · Zener Diodes · SOT-23

SZMMBZ5257BLT1G from onsemi, 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 | ANODE | passive | Anode terminal of the Zener diode; the datasheet pinout is 1-Anode, 2-No Connection, 3-Cathode. |
| 2 | NC | unconnected | No connection; the datasheet specifies no electrical function for this pin. |
| 3 | CATHODE | passive | Cathode terminal of the Zener diode, identified by the polarity band on the package. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | onsemi |
| Package | SOT-23 |
| Category | Diodes |
| Pins | 3 |

## Electrical characteristics

Limits as printed in the datasheet (page.json `metadata.characteristics` carries them as data).

| Parameter | Symbol | Min | Typ | Max | Unit | Conditions | Page |
|---|---|---|---|---|---|---|---|
| Peak Power Dissipation (@ TL ≤ 25°C) | Ppk |  |  | 225 | W | @ 20 s (Note 1), @ TL ≤ 25°C | 1 |
| Total Power Dissipation on FR-5 Board (Note 2) | PD |  |  | 225 | mW | @ TA = 25°C | 1 |
| Derating above 25°C, FR-5 Board | PD |  |  | 1.8 | mW/°C | Derated above 25°C, FR-5 board | 1 |
| Thermal Resistance, Junction-to-Ambient, FR-5 Board | RJA |  |  | 556 | °C/W | FR-5 board (Note 2) | 1 |
| Total Power Dissipation on Alumina Substrate (Note 3) | PD |  |  | 300 | mW | @ TA = 25°C, alumina substrate | 1 |
| Derating above 25°C, Alumina Substrate | PD |  |  | 2.4 | mW/°C | Derated above 25°C, alumina substrate | 1 |
| Thermal Resistance, Junction-to-Ambient, Alumina Substrate | RJA |  |  | 417 | °C/W | Alumina substrate (Note 3) | 1 |
| Junction and Storage Temperature Range | TJ, Tstg | -65 |  | 150 | °C |  | 1 |

## CAD (KiCad official)

- Symbol: `SZMMBZ5257BLT1G`
- Footprint: `Package_TO_SOT_SMD:SOT-23`
- 3D model: SOT-23 (KiCad packages3D, STEP)
- 3D model files: `szmmbz5257blt1g-etched.step` / `szmmbz5257blt1g-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `szmmbz5257blt1g.step` / `szmmbz5257blt1g.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [onsemi datasheet](https://jlcpcb.com/api/file/downloadByFileSystemAccessId/8590448108619530240) (7 pp, sha256 `2d00837373f04706`, retrieved 2026-10-18, 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/szmmbz5257blt1g-datasheet.pdf)