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Do push button switch signals require aTVS diode in the path?

I have seen TVS diodes for push button switch signals in many circuits along with pull resistor, capacitor (RC for debouncing) as in this image:

enter image description here

What is the exact purpose of TS6 TVS diode? As I understanding it, TVS diodes are used to suppress high voltage spikes.

What condition can cause high voltage spikes in the button signal in the above image?

Even when the switch is pressed , C2 discharges through 1.5K resistor which avoids sudden discharge through low resistance load.

I understood it as high voltage spikes occur only when a capacitor suddenly discharges through a low resistance load, but there is 1.5K resistor present in the discharge path. What is the exact need for a TVS diode here? Please correct me if my understanding is wrong.

JRE
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Sathish
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1 Answers1

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The TVS is there to catch high voltage peaks that can occur when YOU touch the button.

There is no high voltage source in the circuit that could produce high voltage.

The human body is, however, a fairly decent high voltage generator. You can easily build up a potential of several thousand volts just by walking on a dry day.

If your body is charged up, then you can cause damage to the circuit by touching the button.

Actual damage is fairly rare. Many circuits don't bother with a TVS or other over voltage protection.

Whether you need it or not depends on a lot of things.

Is this a hobby project? Well, odds are you don't need the TVS.

Is this part of a control circuit for a medical device that could kill someone if it misbehaves? Probably best include the TVS (and many other things that are required for medical safety.)

There are millions (billions? trillions?) of electronic toys that don't have over voltage protection. We don't have a huge flood of devices dying every day from getting zapped by their users, so the odds are pretty much against it being a problem.

JRE
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    Thanks for the comment! Is there possibility for ESD from human body affects the circuit when using plastic insulated cap on push button switch? – Sathish May 30 '18 at 11:41
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    Yes. Even plastic can act as a conductor if the voltage is high enough - heck, if the voltage is high enough, the air around the switch can be regarded as a conductor. – JRE May 30 '18 at 13:52
  • Thank you very much for the response i feel it very useful! – Sathish May 30 '18 at 13:56