How can I protect MCU pins connected to external circuits from ESD damage?
When traces from MCU pins are routed to external circuits outside the PCB or to headers or connectors, those traces may experience electrostatic discharge (ESD), latch-up, or even possibly share signals with other systems with no common ground potential. MCU pins can be protected from such conditions in many ways:
* Galvanic Isolation
* Transorbs or Schottky Diodes
Each of the above methods of protection and a detailed discussion on latch-up, ESD and ground loops can be found in AN203 'C8051Fxxx Printed Circuit Board Design Notes' in section 5 'Isolation and Protection' and in Appendix A. This application note can be downloaded from here:
For protecting USB D+, D-, and VBUS pins from ESD events, see the article linked in the 'Related Articles' section below.