Please i need help : i have two separated electronic cricuit that communicate via uart, see attached, i didn't put directly the RX and TX of the two circuit i added transistor, i need help on how to protect my circuit from ESD or another protection
If you add a pair of diodes to each input and output at the transistor base/collector. one diode anode to ground, cathode to base/collector, another anode to base/collector , cathode to Vcc. This will clamp any incoming voltage on the line to, between, ground-.8V or Vcc +.8V.
Frank
Series resistors (of not too small physical size!) already provide a lot of protection since they help to limit peak currents. Same goes for buffer transistors on inputs & outputs since they provide alternative current paths in case of ESD events. Proper connectors & cabling can make sure that ground points always contact before signal pins, making ESD problems unlikely (at least, from connecting/disconnecting equipment).