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Answer to this question says that the voltage across a capacitor on an ESD event (see the link for used values) would be 8 V. Can I use it to protect MOSFET drain pin that could be touched during manufacturing or repairs (it is connected to a pin header)? I know that a TVS diode would be better, but the 100n capacitor is already on the BOM.

The load is non-inductive and it is switched only on low frequencies.

schematic

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  • \$\begingroup\$ Seems extremely excessive. MOSFETs these days are many orders of magnitude more ESD tolerant than their 1970 grandfathers. \$\endgroup\$
    – winny
    Sep 3, 2022 at 14:21
  • \$\begingroup\$ This one has absolute max. Vds = 20V. \$\endgroup\$
    – jiwopene
    Sep 3, 2022 at 14:25
  • \$\begingroup\$ Or do you think that it would tolerate ESD without the capacitor well? There will be approx. 1ft/30cm wire connected to the connector. \$\endgroup\$
    – jiwopene
    Sep 3, 2022 at 14:27
  • \$\begingroup\$ 99.99 % chance of survival. If you have ESD issues, you be better off with something else, probably a transil. \$\endgroup\$
    – winny
    Sep 3, 2022 at 15:49
  • \$\begingroup\$ How fast is the gate drive (direct wire to logic pin? series resistor, what value? etc.)? \$\endgroup\$ Sep 3, 2022 at 18:08

2 Answers 2

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Can I use it to protect MOSFET drain pin that could be touched during manufacturing or repairs

Nobody should be manufacturing an electronics board or repairing it without anti-static wristbands and a proper anti-static mat. It's not just the MOSFET that could become damaged but any sensitive item on the PCB assembly. That just about includes any IC used (with few exceptions).

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  • \$\begingroup\$ This will be a driver board (transistors + few not-so-much sensitive components) that will get mounted in the place of the final product. I think that it is better to get safer by protecting the FETs. \$\endgroup\$
    – jiwopene
    Sep 3, 2022 at 16:11
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Yes it probably would within the confines of the Human Body Model. Be careful though, the HMB is only a model.

If the capacitor is permanently attached and not removed after assembly, the capacitor will discharge through the FET whenever it turns on. This could easily stress the FET during operation.

You have a trade off. You should heed Andy aka's advice.

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