I have the schematic below.

It works fine and has done so for a few months. However, today, it seems the PIC USB module has died when I powered off/on the board.

Is there more input protection needed? Is the VBUS need some protection as well ?

The board is externally powered through an isolated AC/DC supply.

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  • \$\begingroup\$ Why do you question only your board and not that external supply? I do not understand why on the IC pin 2 is GND while in your circuit pin 2 is one of the signals. \$\endgroup\$ – Bimpelrekkie May 9 at 11:38
  • \$\begingroup\$ I think you are looking at the connector. \$\endgroup\$ – Damien May 12 at 18:02
  • \$\begingroup\$ Indeed, I mistook the connector for the protection device. Then you already have Vbus protection, there's a zener in the protection device between Vbus and GND. In my opinion you have done all that's needed to protect the internal circuit from the USB connector. \$\endgroup\$ – Bimpelrekkie May 12 at 18:43

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