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I am designing a circuit for a microcontroller that has a few 3.3V GPIO pins. I heard from somewhere that adding small resistor of around 100 ohms in series with the GPIO, will add some additional power surge protection, but I am not quite sure how, and have had trouble finding any sources that can back this up.

Schematic with 100 ohm resistor in series with GPIO pins

Is it true that these resistors will help protect the GPIO from power surges, and does this design principle have a name that can be googled?

I assume that using this method, limits the GPIOs to signalling high-impedance inputs, like other MCU's and MOSFETs. Are there any other negatives i should worry about?

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    \$\begingroup\$ Someone once said: "I Do Not Think It Means What You Think It Means"... so what do you think "power surge" means, and how do you think it applies to your GPIO pins? \$\endgroup\$
    – brhans
    Commented Apr 10, 2021 at 15:08
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    \$\begingroup\$ It depends on what you mean by "power surge". They certainly won't provide much protection from overvoltage applied to the pin. For every volt of excess voltage, you'll get another 10 mA of current, and it doesn't take a lot of current to blow a pin. Usually, such resistors are intended to limit the current if the external pin is shorted to ground while the MCU pin is configured as an output. \$\endgroup\$
    – Dave Tweed
    Commented Apr 10, 2021 at 15:09

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Assuming that you mean ESD (electrostatic discharge), then - NO. There are special diodes called "Transil" which suppress transient voltage spikes. (almost) All modern microcontrollers have diodes on input for input protection, so unless you want to protect chip from serious, high energy ESD discharges (like in human body model), than you don't need additional protection.

Assuming that you mean long line driving with digital signal- YES, that will limit surge current. BUT - this will also increase line charging time and spoil shape of your signal.

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    \$\begingroup\$ A lot of good knowledge, concisely written. +1 \$\endgroup\$
    – jonk
    Commented Apr 10, 2021 at 19:02

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