MCU protection circuit / IC


#1

Hi

I want to protect digital inputs C0-C3 on electron from over voltage and induction peaks in wire from other controller.

Question: Is solution in attached link (figure 13) with discrete elements only way or are some integrated IC on the market. I would need 4 or more channel protection IC.

Thank you
Primož

https://www.digikey.com/en/articles/techzone/2012/apr/protecting-inputs-in-digital-electronics
image


#2

There are potentially a few things here:

  1. The long wire acts like an ariel and picks up EMC - this can be protected against by using shielded cable grounded at the MCU end.
  2. The switch output signal doesn’t appear to have a common ground with the PCB - this needs to be fixed with a ground wire to the switched otherwise there could be a difference in ground levels.
  3. With a 5V supply from the PCB I would protect from over voltage with a zener diode and a small value resistor for limiting the current 100ohms. The schematic has that but also a lot of other components that may not be necessary.
  4. If the input voltage is 12VDC then you could use a suitable opto coupler - this has the advantage of completely protecting the MCU and could be 3V3 logic level. This also might be a cheaper option.

#3

Thank you for your remarks. I need to study those ground levels.

Electron will be powered from that same controller (control switch) with 35V to 5V via some LDO (not isolated https://www.we-online.de/katalog/en/pm/MAGIC_FDSM_FIXED_OUTPUT_VOLTAGE). So I assume that ground level will be the same for this digital line. Level of signal will be 5V.

If the ground level is same (from power line), can I wire 4 signals without ground wire pair?