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I have to select the best safe solution to protect a 5V input.

Below are four solutions that I have designed to protect my 5V input against over voltage using a varistor and a TVS.

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Different solutions are available. I'm really confused which solution to choose.

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  • \$\begingroup\$ You have to look at what the source of the overvoltage looks like and what the input looks like that you are trying to protect. None of those looks very useful. \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Jan 24, 2021 at 16:59
  • \$\begingroup\$ @SpehroPefhany: it's an input to connect for example a microcontroller power supply. \$\endgroup\$
    – geek225
    Commented Jan 24, 2021 at 17:10
  • \$\begingroup\$ So what connects where and how much voltage can the input stand without damage (in either polarity) and what is the fault source impedance? For example, if it can withstand 45V then a 26V TVS will (barely) provide protection against a 14A surge. \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Jan 24, 2021 at 17:12
  • \$\begingroup\$ @geek225 that sadly doesn't answer the question of "what's the source of the overvoltage"; what Spehro is telling you: There's different kinds of things that are "overvoltage", which come from different kind of phenomena, and do different kind of damage, and need to be protected against differently. Without knowing against what you're protecting, there isn't an effective protection. \$\endgroup\$
    – Marcus Müller
    Commented Jan 24, 2021 at 17:12
  • \$\begingroup\$ @SpehroPefhany: Thanks for your reply. I want to protect my "5 V " power supply input againt an overvolatge of 26V. e.g a bad connection \$\endgroup\$
    – geek225
    Commented Jan 24, 2021 at 17:20

1 Answer 1

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I wouldn't use a TVS or varistors to protect the 5V from an overvoltage. Instead, I would use a Zener clamping circuit or an IC that provides an overvoltage protection. TVS/varistors are more suited for fast transients. Unlike overvoltages, the voltage would remain for longer period and requires a 'resolve' either through clamping or cutoff when a fault is detected.

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  • \$\begingroup\$ Hi and welcome -- I'm curious, could you explain the distinction between TVS (assuming the common zener/avalanche type) and zener? \$\endgroup\$
    – Tim Williams
    Commented Mar 18, 2023 at 13:55
  • \$\begingroup\$ How precise should the overvoltage protection be? Is 5.01V to much or are 5.5V overvoltage still okay? What type of overvoltage source do you have? \$\endgroup\$
    – MikroPower
    Commented Mar 18, 2023 at 17:19

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