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MMBZ5257BLT1G
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onsemi Zener Diodes, SOT-23. Pinout cross-checked by two models against the datasheet, KiCad symbol/footprint/3D.
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MMBZ5257BLT1G
onsemi · Zener Diodes · SOT-23
MMBZ5257BLT1G 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 of the 33 V Zener diode (MMBZ5257B, VZ 31.35 V min to 34.65 V max at IZT = 3.8 mA). |
| 2 | NC | unconnected | No connection (SOT-23 CASE 318 Style 8). |
| 3 | Cathode | passive | Cathode of the Zener diode, marked by the polarity band, which is the reverse Zener voltage terminal. |
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 |
|---|---|---|---|---|---|---|---|
| Zener Voltage | VZ | 31.35 | 33 | 34.65 | V | @ IZT = 3.8 mA, TA = 25°C | 3 |
| Zener Test Current | IZT | 3.8 | mA | test current for VZ and ZZT | 3 | ||
| Zener Impedance | ZZT | 58 | Ω | @ IZT = 3.8 mA | 3 | ||
| Zener Impedance | ZZK | 700 | Ω | @ IZK = 0.25 mA | 3 | ||
| Reverse Leakage Current | IR | 0.1 | µA | @ VR = 25 V | 3 | ||
| Forward Voltage | VF | 0.9 | V | IF = 10 mA, all types | 3 | ||
| Total Power Dissipation on FR-5 Board | PD | 225 | mW | TA = 25°C, FR-5 board (Note 1) | 1 | ||
| Power Derating above 25°C (FR-5) | PD | 1.8 | mW/°C | FR-5 board, above 25°C | 1 | ||
| Total Power Dissipation on Alumina Substrate | PD | 300 | mW | TA = 25°C, alumina substrate (Note 2) | 1 | ||
| Power Derating above 25°C (Alumina) | PD | 2.4 | mW/°C | Alumina substrate, above 25°C | 1 | ||
| Junction and Storage Temperature Range | TJ, Tstg | -65 | 150 | °C | 1 | ||
| Thermal Resistance, Junction-to-Ambient (FR-5) | RθJA | 556 | °C/W | FR-5 board (Note 1) | 1 | ||
| Thermal Resistance, Junction-to-Ambient (Alumina) | RθJA | 417 | °C/W | Alumina substrate (Note 2) | 1 | ||
| Maximum Case Temperature for Soldering | 260 | °C | 10 seconds | 1 |
CAD (KiCad official)
- Symbol:
MMBZ5257BLT1G - Footprint:
Package_TO_SOT_SMD:SOT-23 - 3D model: SOT-23 (KiCad packages3D, STEP)
- 3D model files:
mmbz5257blt1g-etched.step/mmbz5257blt1g-etched.glbcarry the MPN laser-etched on the die in a toggleableAdom.LaserEtchgroup (Fusion-ready);mmbz5257blt1g.step/mmbz5257blt1g.glbare the bare package body.
Provenance
Data extracted from the manufacturer datasheet, not a distributor listing:
- Datasheet: onsemi datasheet (7 pp, sha256
1e037aa419653ef8, retrieved 2026-10-23, tier: manufacturer) - Extractor: parts-factory
2.0.0/extract_pins 0.3, primaryclaude-sonnet-5-5(text), consensusclaude-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).
# MMBZ5257BLT1G
**onsemi** · Zener Diodes · SOT-23
MMBZ5257BLT1G 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 of the 33 V Zener diode (MMBZ5257B, VZ 31.35 V min to 34.65 V max at IZT = 3.8 mA). |
| 2 | NC | unconnected | No connection (SOT-23 CASE 318 Style 8). |
| 3 | Cathode | passive | Cathode of the Zener diode, marked by the polarity band, which is the reverse Zener voltage terminal. |
## 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 |
|---|---|---|---|---|---|---|---|
| Zener Voltage | VZ | 31.35 | 33 | 34.65 | V | @ IZT = 3.8 mA, TA = 25°C | 3 |
| Zener Test Current | IZT | | 3.8 | | mA | test current for VZ and ZZT | 3 |
| Zener Impedance | ZZT | | | 58 | Ω | @ IZT = 3.8 mA | 3 |
| Zener Impedance | ZZK | | | 700 | Ω | @ IZK = 0.25 mA | 3 |
| Reverse Leakage Current | IR | | | 0.1 | µA | @ VR = 25 V | 3 |
| Forward Voltage | VF | | | 0.9 | V | IF = 10 mA, all types | 3 |
| Total Power Dissipation on FR-5 Board | PD | | | 225 | mW | TA = 25°C, FR-5 board (Note 1) | 1 |
| Power Derating above 25°C (FR-5) | PD | | | 1.8 | mW/°C | FR-5 board, above 25°C | 1 |
| Total Power Dissipation on Alumina Substrate | PD | | | 300 | mW | TA = 25°C, alumina substrate (Note 2) | 1 |
| Power Derating above 25°C (Alumina) | PD | | | 2.4 | mW/°C | Alumina substrate, above 25°C | 1 |
| Junction and Storage Temperature Range | TJ, Tstg | -65 | | 150 | °C | | 1 |
| Thermal Resistance, Junction-to-Ambient (FR-5) | RθJA | | | 556 | °C/W | FR-5 board (Note 1) | 1 |
| Thermal Resistance, Junction-to-Ambient (Alumina) | RθJA | | | 417 | °C/W | Alumina substrate (Note 2) | 1 |
| Maximum Case Temperature for Soldering | | | | 260 | °C | 10 seconds | 1 |
## CAD (KiCad official)
- Symbol: `MMBZ5257BLT1G`
- Footprint: `Package_TO_SOT_SMD:SOT-23`
- 3D model: SOT-23 (KiCad packages3D, STEP)
- 3D model files: `mmbz5257blt1g-etched.step` / `mmbz5257blt1g-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `mmbz5257blt1g.step` / `mmbz5257blt1g.glb` are the bare package body.
## Provenance
Data extracted from the manufacturer datasheet, not a distributor listing:
- **Datasheet:** [onsemi datasheet](https://www.onsemi.com/pdf/datasheet/mmbz5257blt1-d.pdf) (7 pp, sha256 `1e037aa419653ef8`, retrieved 2026-10-23, tier: manufacturer)
- **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/mmbz5257blt1g-datasheet.pdf)