I've read about ESD protection with capacitors and it seems that if one knows its limitations it could in some cases be a cheap alternative for or addition to designated ESD protection circuits.
The basic idea is that the charge of the ESD source (i.e. Human Body Model) will be shared across the source's capacitor and the "protective capacitor". The final voltage could then be estimated using simple calculations. ()
But what if the "protective capacitor" is already fully charged when the ESD event occurs? For example, let's say it is a charged input capacitor of a voltage regulator and a ESD event occurs at its input connector. Does it then still provide any protection?
Any clarification would be appreciated.