Post History
I previously had failures where the MOSFET (Q1) got damaged. ESD can damage MOSFETs with an exposed drain. I've seen that before. Is using a PESD18VS1UA (18V TVS) on the drain appropriat...
#3: Post edited
by
Nick Alexeev
·
2025-10-23T00:18:37Z (11 months ago)
- > I previously had failures where the MOSFET (Q1) got damaged.
ESD can damage MOSFETs with eposed drain. I've seen that before.- > 1. Is using a PESD18VS1UA (18V TVS) on the drain appropriate for a 5V LED line, or should I switch to a 5V bidirectional TVS instead?
- Not finding the datasheet for your 18V part. For the purposes of the answer, let's go with the 12V equivalent PESD12VS1UA ([datasheet](https://assets.nexperia.com/documents/data-sheet/PESD12VS1UA.pdf)). It clamps at 27V, and the MOSFET is rated for 30V max V<sub>DS</sub>. There's not a lot of margin left. I'd look for a TVS which clamps at 20V or less.
- You should use a unidirectional TVS. The PESD12VS1UA can clamp negative ESD pulses. See fig. 8 in the datasheet.
- [Please get into a habit of posting datasheet links for the lazy volunteers. ]
- > 2. Do I also need a 5V to GND TVS on the power rail near the connector, or is the drain clamp sufficient?
- Maybe you can survive without a TVS for the 5V rail at the connector. But such TVS wouldn't hurt.
- Capacitors can arrest ESD pulses too. There are ESD-rated ceramic capacitors (some discussion [here](https://electrical.codidact.com/posts/279876/280125#answer-280125)). The capacitor would have to be placed next to the connector. Otherwise the ESD may jump from the power supply rail somewhere more sensitive.
- > [D6 for gate protection] Do we need gate protection?
In this case you don't require ESD protection for the gate. The gate isn't eposed. Drain protection will catch the ESD.
- > I previously had failures where the MOSFET (Q1) got damaged.
- ESD can damage MOSFETs with an exposed drain. I've seen that before.
- > 1. Is using a PESD18VS1UA (18V TVS) on the drain appropriate for a 5V LED line, or should I switch to a 5V bidirectional TVS instead?
- Not finding the datasheet for your 18V part. For the purposes of the answer, let's go with the 12V equivalent PESD12VS1UA ([datasheet](https://assets.nexperia.com/documents/data-sheet/PESD12VS1UA.pdf)). It clamps at 27V, and the MOSFET is rated for 30V max V<sub>DS</sub>. There's not a lot of margin left. I'd look for a TVS which clamps at 20V or less.
- You should use a unidirectional TVS. The PESD12VS1UA can clamp negative ESD pulses. See fig. 8 in the datasheet.
- [Please get into a habit of posting datasheet links for the lazy volunteers. ]
- > 2. Do I also need a 5V to GND TVS on the power rail near the connector, or is the drain clamp sufficient?
- Maybe you can survive without a TVS for the 5V rail at the connector. But such TVS wouldn't hurt.
- Capacitors can arrest ESD pulses too. There are ESD-rated ceramic capacitors (some discussion [here](https://electrical.codidact.com/posts/279876/280125#answer-280125)). The capacitor would have to be placed next to the connector. Otherwise the ESD may jump from the power supply rail somewhere more sensitive.
- > [D6 for gate protection] Do we need gate protection?
- In this case you don't require ESD protection for the gate. The gate isn't eposed. Drain protection will catch the ESD.
- > The LED [which is powered by the MOSFET] is often touched by the human because the led panel has push button also.
- I haven't seen ESD jump from the case of an LED to the pins. Consider grounding the panel to which the LED is attached. A grounded panel will divert the ESD away from the circuit board.
#2: Post edited
by
Nick Alexeev
·
2025-10-22T22:38:07Z (11 months ago)
- > I previously had failures where the MOSFET (Q1) got damaged.
- ESD can damage MOSFETs with eposed drain. I've seen that before.
- > 1. Is using a PESD18VS1UA (18V TVS) on the drain appropriate for a 5V LED line, or should I switch to a 5V bidirectional TVS instead?
- Not finding the datasheet for your 18V part. For the purposes of the answer, let's go with the 12V equivalent PESD12VS1UA ([datasheet](https://assets.nexperia.com/documents/data-sheet/PESD12VS1UA.pdf)). It clamps at 27V, and the MOSFET is rated for 30V max V<sub>DS</sub>. There's not a lot of margin left. I'd look for a TVS which clamps at 20V or less.
- You should use a unidirectional TVS. The PESD12VS1UA can clamp negative ESD pulses. See fig. 8 in the datasheet.
- [Please get into a habit of posting datasheet links for the lazy volunteers. ]
- > 2. Do I also need a 5V to GND TVS on the power rail near the connector, or is the drain clamp sufficient?
- Maybe you can survive without a TVS for the 5V rail at the connector. But such TVS wouldn't hurt.
Capacitors can arrest ESD pulses too. There are ESD-rated ceramic capacitors. Such capacitor would have to be placed next to the connector. Otherwise the ESD may jump from the power supply rail somewhere more sensitive.- > [D6 for gate protection] Do we need gate protection?
- In this case you don't require ESD protection for the gate. The gate isn't eposed. Drain protection will catch the ESD.
- > I previously had failures where the MOSFET (Q1) got damaged.
- ESD can damage MOSFETs with eposed drain. I've seen that before.
- > 1. Is using a PESD18VS1UA (18V TVS) on the drain appropriate for a 5V LED line, or should I switch to a 5V bidirectional TVS instead?
- Not finding the datasheet for your 18V part. For the purposes of the answer, let's go with the 12V equivalent PESD12VS1UA ([datasheet](https://assets.nexperia.com/documents/data-sheet/PESD12VS1UA.pdf)). It clamps at 27V, and the MOSFET is rated for 30V max V<sub>DS</sub>. There's not a lot of margin left. I'd look for a TVS which clamps at 20V or less.
- You should use a unidirectional TVS. The PESD12VS1UA can clamp negative ESD pulses. See fig. 8 in the datasheet.
- [Please get into a habit of posting datasheet links for the lazy volunteers. ]
- > 2. Do I also need a 5V to GND TVS on the power rail near the connector, or is the drain clamp sufficient?
- Maybe you can survive without a TVS for the 5V rail at the connector. But such TVS wouldn't hurt.
- Capacitors can arrest ESD pulses too. There are ESD-rated ceramic capacitors (some discussion [here](https://electrical.codidact.com/posts/279876/280125#answer-280125)). The capacitor would have to be placed next to the connector. Otherwise the ESD may jump from the power supply rail somewhere more sensitive.
- > [D6 for gate protection] Do we need gate protection?
- In this case you don't require ESD protection for the gate. The gate isn't eposed. Drain protection will catch the ESD.
#1: Initial revision
by
Nick Alexeev
·
2025-10-22T22:34:39Z (11 months ago)
> I previously had failures where the MOSFET (Q1) got damaged. ESD can damage MOSFETs with eposed drain. I've seen that before. > 1. Is using a PESD18VS1UA (18V TVS) on the drain appropriate for a 5V LED line, or should I switch to a 5V bidirectional TVS instead? Not finding the datasheet for your 18V part. For the purposes of the answer, let's go with the 12V equivalent PESD12VS1UA ([datasheet](https://assets.nexperia.com/documents/data-sheet/PESD12VS1UA.pdf)). It clamps at 27V, and the MOSFET is rated for 30V max V<sub>DS</sub>. There's not a lot of margin left. I'd look for a TVS which clamps at 20V or less. You should use a unidirectional TVS. The PESD12VS1UA can clamp negative ESD pulses. See fig. 8 in the datasheet. [Please get into a habit of posting datasheet links for the lazy volunteers. ] > 2. Do I also need a 5V to GND TVS on the power rail near the connector, or is the drain clamp sufficient? Maybe you can survive without a TVS for the 5V rail at the connector. But such TVS wouldn't hurt. Capacitors can arrest ESD pulses too. There are ESD-rated ceramic capacitors. Such capacitor would have to be placed next to the connector. Otherwise the ESD may jump from the power supply rail somewhere more sensitive. > [D6 for gate protection] Do we need gate protection? In this case you don't require ESD protection for the gate. The gate isn't eposed. Drain protection will catch the ESD.