Combat ESD for micro on PCB

[cupoftea]

Hi,
If you have a micro on a PCB, and one of its inputs comes from a cable from a different PCB, then how do you combat potential ESD problems to the micro input pin?

As you know, you can do

1...Series resistor into micro pin, and (small) filter cap on micro pin.
2...ESD diodes from the micro input to Vdd and Vss of micro.
3.....TVS on the micro input.

But which of these is the best, and when would you use all of these?

 

[KlausST]

Hi,

It depends on the signal of the line.

If it needs to be low impedance, then you can't use a series resistance.
If it needs to be a very precise analog signal you have to take care of leakage currents of diodes or TVS
If it needs to be a high speed signal, then you have to take care about stray capacitance.
...

Also you may decide the worst case ESD voltage and energy. ...in both directions.

For low energy, low current ESP pulses a (double) diode like BAT54S could be sufficient. I like the idea of a series resistor, it limits the current, dissipates pulse energy and reduces/avoids ringing

Klaus