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ZMM5257B
Public Made by Adomby adom
ST Semtech Zener Diodes, MiniMELF. Unpolarised two-terminal part: the datasheet prints no pin numbers, so pins 1 and 2 follow the library convention, KiCad symbol/footprint/3D.
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ZMM5257B
ST Semtech · Zener Diodes · MiniMELF
ZMM5257B from ST Semtech, in a MiniMELF. 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: the banded/marked end per the datasheet; pad 1 of the KiCad diode footprint. |
| 2 | A | passive | Anode. |
Key specifications
| Parameter | Value |
|---|---|
| Manufacturer | ST Semtech |
| Package | MiniMELF |
| 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 tolerance (suffix B) | -5 | 5 | % | Suffix B = ±5% tolerance | 1 | ||
| Zener voltage (VZ at IZT = 3.8 mA) | VZT | 31.35 | 33 | 34.65 | V | at IZT = 3.8 mA; VZnom 33 V | 2 |
| Dynamic resistance | ZZT | 58 | Ω | at IZT = 3.8 mA; tested with pulses tp = 20 ms | 2 | ||
| Dynamic resistance (knee) | ZZK | 700 | Ω | at IZK = 0.25 mA | 2 | ||
| Reverse current | IR | 0.1 | µA | at VR = 25 V | 2 | ||
| Forward voltage | VF | 1.1 | V | at IF = 200 mA | 1 | ||
| Power dissipation | Ptot | 500 | mW | Valid provided that electrodes are kept at ambient temperature | 1 | ||
| Junction temperature | Tj | 175 | °C | 1 | |||
| Storage temperature range | Tstg | -65 | 175 | °C | 1 | ||
| Thermal resistance junction to ambient air | RthA | 0.3 | K/mW | Valid provided that electrodes are kept at ambient temperature | 1 |
CAD (KiCad official)
- Symbol:
ZMM5257B - Footprint:
Diode_SMD:D_MiniMELF - 3D model: MiniMELF (KiCad packages3D, STEP)
Provenance
Data extracted from the manufacturer datasheet, not a distributor listing:
- Datasheet: ST Semtech datasheet (3 pp, sha256
a48a7bc3e88e9776, retrieved 2026-10-16, tier: lcsc) - Extractor: parts-factory
2.0.0/extract_pins, primarycathode-band convention(convention), consensusoff(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).
# ZMM5257B
**ST Semtech** · Zener Diodes · MiniMELF
ZMM5257B from ST Semtech, in a MiniMELF. 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: the banded/marked end per the datasheet; pad 1 of the KiCad diode footprint. |
| 2 | A | passive | Anode. |
## Key specifications
| Parameter | Value |
|---|---|
| Manufacturer | ST Semtech |
| Package | MiniMELF |
| 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 tolerance (suffix B) | | -5 | | 5 | % | Suffix B = ±5% tolerance | 1 |
| Zener voltage (VZ at IZT = 3.8 mA) | VZT | 31.35 | 33 | 34.65 | V | at IZT = 3.8 mA; VZnom 33 V | 2 |
| Dynamic resistance | ZZT | | | 58 | Ω | at IZT = 3.8 mA; tested with pulses tp = 20 ms | 2 |
| Dynamic resistance (knee) | ZZK | | | 700 | Ω | at IZK = 0.25 mA | 2 |
| Reverse current | IR | | | 0.1 | µA | at VR = 25 V | 2 |
| Forward voltage | VF | | | 1.1 | V | at IF = 200 mA | 1 |
| Power dissipation | Ptot | | | 500 | mW | Valid provided that electrodes are kept at ambient temperature | 1 |
| Junction temperature | Tj | | | 175 | °C | | 1 |
| Storage temperature range | Tstg | -65 | | 175 | °C | | 1 |
| Thermal resistance junction to ambient air | RthA | | | 0.3 | K/mW | Valid provided that electrodes are kept at ambient temperature | 1 |
## CAD (KiCad official)
- Symbol: `ZMM5257B`
- Footprint: `Diode_SMD:D_MiniMELF`
- 3D model: MiniMELF (KiCad packages3D, STEP)
## Provenance
Data extracted from the manufacturer datasheet, not a distributor listing:
- **Datasheet:** [ST Semtech datasheet](https://jlcpcb.com/api/file/downloadByFileSystemAccessId/8586193369580654592) (3 pp, sha256 `a48a7bc3e88e9776`, retrieved 2026-10-16, tier: lcsc)
- **Extractor:** parts-factory `2.0.0` / `extract_pins`, primary `cathode-band convention` (convention), consensus `off` (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/zmm5257b-datasheet.pdf)