# MMBZ5251BLT1G

**onsemi** · Zener Diodes · SOT-23

MMBZ5251BLT1G 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 gives the pinout only (Style 8: pin 1 = Anode) and no pin-specific electrical limits, with the device forward voltage VF specified as 0.95 V max at IF = 10 mA. |
| 2 | NC | unconnected | No connection (Style 8: pin 2 = No Connection); the datasheet pinout lists this pin as not internally connected. |
| 3 | Cathode | passive | Cathode terminal of the Zener diode, identified on the package by the polarity band; the datasheet gives no pin-specific electrical limits beyond the device ratings. |

## 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 |
|---|---|---|---|---|---|---|---|
| Reverse Zener Voltage (22 V nominal, 81B) | VZ | 20.9 | 22 | 23.1 | V | @ IZT 5.6 mA; pulse test at TA = 25°C (Note 3) | 3 |
| Maximum Zener Impedance | ZZT |  |  | 29 | Ω | @ IZT 5.6 mA | 3 |
| Maximum Zener Impedance | ZZK |  |  | 600 | Ω | @ IZK 0.25 mA | 3 |
| Reverse Leakage Current | IR |  |  | 0.1 | µA | @ VR 17 V | 3 |
| Forward Voltage | VF |  |  | 0.9 | V | @ IF 10 mA | 3 |
| Total Power Dissipation on FR-5 Board | PD |  |  | 225 | mW | TA = 25°C; FR-5 board (Note 1) | 1 |
| Derating above 25°C (FR-5 Board) | PD |  |  | 1.8 | mW/°C | Derated above 25°C; FR-5 board (Note 1) | 1 |
| Total Power Dissipation on Alumina Substrate | PD |  |  | 300 | mW | TA = 25°C; alumina substrate (Note 2) | 1 |
| Derating above 25°C (Alumina Substrate) | PD |  |  | 2.4 | mW/°C | Derated above 25°C; alumina substrate (Note 2) | 1 |
| Thermal Resistance, Junction-to-Ambient (FR-5 Board) | RJA |  |  | 556 | °C/W | FR-5 board (Note 1) | 1 |
| Thermal Resistance, Junction-to-Ambient (Alumina Substrate) | RJA |  |  | 417 | °C/W | Alumina substrate (Note 2) | 1 |
| Junction and Storage Temperature Range | TJ, Tstg | -65 |  | 150 | °C |  | 1 |

## CAD (KiCad official)

- Symbol: `MMBZ5251BLT1G`
- Footprint: `Package_TO_SOT_SMD:SOT-23`
- 3D model: SOT-23 (KiCad packages3D, STEP)
- 3D model files: `mmbz5251blt1g-etched.step` / `mmbz5251blt1g-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `mmbz5251blt1g.step` / `mmbz5251blt1g.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/8558971945192103936) (7 pp, sha256 `ab7a3f113b952d5a`, 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/mmbz5251blt1g-datasheet.pdf)