This is a rather big topic. It is really quite important to consider how static discharge could affect your product through any of its i/o or power inputs or even switches or other openings in the case. I usually employ a combination of a ferrite bead, ceramic capacitor, and tvs diode on every wire which leaves or enters the pub. Sometimes this scheme must be modified because the signal on said wire is too high frequency or carries too much current. But the general strategy is absorb-block-clamp. The capacitor helps to convert a very short high voltage pulse into a longer duration but much smaller amplitude pulse (absorb). The ferrite bead limits the current in the fast pulse so that parasitic inductance in the ground path and in the capacitor do not develop a high voltage drop. (Block= ) Finally, the tvs diode clamps the remaining pulse to no greater than the max rated voltage of the i/o pin. (Clamp) So the ferrite bead would be located nearest the outside world, and then the cap and tvs diode would be in parallel between the signal line and gnd after the ferrite. I also like to maintain a separate ground "ring" around the perimeter of the board which connects to the rest of the ground plane at only one point. The tvs diodes and esd-related caps connect to this ground and this ground is also the only connection to chassis (not always feasible when you have RF signals) This ground ensures that transient high voltage drops due to fast was pulses do not develop between locations on the main ground plane. In the end, all of this must be tested and any remaining vulnerabilities corrected. I have designed 4 or 5 high volume (10k to 200k) industrial products using variations of this strategy with no problems passing esd tests and very few known field esd failures. Sean On Feb 10, 2018 12:44 PM, "Chuck Olson" wrote: > Fellows and Gals - > > It's static season here, had a customer complain about a PIC based > product acting strangely - I *think* it's due to static damage. > > He purchased a replacement PIC, I included some small (180 ohm) series > resistors for a couple of inputs - also a 1n4148 diode to attach, > reversed biased, between the programming voltage pin (pin 4 on an 8 > pin PIC) and VDD. > > Just wondering if there are any other tips or tricks I might suggest > to him to help prevent static damage ? > > Chuck > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .