Electronic – ESD Capacitor Calculation, 330Ohm Series Resistor and ESD Clamp Voltage

capacitoresdhigh voltagestaticvoltage

I have a input power filter circuit.

It has ESD Protection capacitors which help to protect the downstream circuit from ESD Pulses.

enter image description here

ESD Capacitors Specifications :

C0001, C0002, C0003, C0004 = 47nF, 100V, 10%, 0805

My ESD Pulse Specifications :

Contact Discharge : +/-4kV & 150pF / 330Ohms

Contact Discharge : +/-8kV & 150pF / 330Ohms

Air Discharge : +/-15kV & 150pF / 330Ohms

My ESD Calculation:

For example, I take the +/-8kV & 150pF spec

Consider the -8kV pulse

Q=CV ;

8kV * 150pF = 1200nC

This Charge will then get to the input ESD Capacitors :

V=Q/C;

1200nC / 23.5nF = 51.06V —– This is less than 200V (both capacitors are connected in series)

Required Capacitance:

enter image description here

=((8000V*150pF)/40V)-150pF = 29.85nF —- Assume my Clamp voltage is 40V at the cathode of D0002

Therefore, the voltage ratings of the capacitors are satisfied. But the required capacitance is very much higher than 23.5nF which I have.

My questions :

  1. Are my calculations of the Required Capacitance section correct? If they are correct, my circuit will fail at -8kV pulse right? What to do in this scenario?

  2. I have never included the 330ohm series resistance in my theroretical calculations. Should I include the 330ohm series resistor in my calculations? If so, where?

  3. On what should should I set my ESD Clamp voltage? In this case, I have set it to 40V since the absolute maximum ratings of the components present in the downstream is 40V? Is it Ok ? Or on what basis should I select my ESD Clamp voltage?

Best Answer

Related Topic