Reverse Polarity Protection Explained: Stop Circuit Damage!

In this video, Tech Consultant Zach Peterson offers an introduction to reverse polarity protection, exploring the best methods to protect your circuits and components from damage. Whether you're a professional PCB designer or an electronics enthusiast, understanding reverse polarity protection is essential.

Zach reviews real-world examples from LinkedIn discussions, covering everything from diodes to P-channel and N-channel MOSFETs, fuses, and resettable protection solutions. You'll learn how to implement these strategies in your own designs, ensuring you safeguard your components and maintain optimal performance.

Plus, Zach explores voltage drop considerations and how to choose the right components for your specific needs. Stay tuned as Zach breaks down the complexities of reverse polarity protection and shows you how to apply these solutions to prevent costly mistakes in your designs.

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0:00 Intro
0:42 Reverse Polarity Protection Community Thoughts
6:12 The Diode & MOSFET Options
10:42 N-Channel MOSFET Option

[mesut]

my lab tests show that doing everything wrong but putting a silkscreen logo of zachs big arms protects my circuit from all evil effects

[miskoLL]

These educational videos are amazing and refreshing! By the way, this is just what I needed as it's a part of my project and Master's thesis as well. Keep it up Zach!

[kiyanvhd]

I'm really glad Zack took my suggestion seriously! 😊

[MrWayneGame]

I am a great fan of reverse polarity tvs diodes, because I once bought a broken device for 80 Euro instead of 400 Euro because the previous owner plugged in the wrong power supply and the tvs diode failed short.
It was an easy repair for me thought.

[hamzakhanrajput]

That's a great video! In my opinion using MOSFETs is the best option in most embedded hardware designs.

[kristianstepancic]

I was just researching this topic to implement on my circuit for the first time, properly.
How did you know??

[FDcombat]

In the case of the P-channel - you mention the leaking current is what makes sure we are in the linear region. What does the calculation actually look like. It is just the leaking current from the mosfet datasheet multiplied with the Resistor (R) to see what the voltage would be - is it that simple? Any other pitfalls to be aware of with this design?

[thomassorensen]

In general I would avoid the N-channel as this puts loss in the common ground. This could lead to a bouncing reference at high current use.

[joemann]

A P-channel MOSFET is usually my favourite but if the input voltage is already on the higher side of what I'd need, a series diode does the trick and is normally a little cheaper for very low cost stuff.

[martinnjoroge]

In the PMOS method, the MOSFET drain terminal is connected to the supply while the source terminal is connected to the circuit. How does this allow current flow yet for MOSFETs, current is from source to drain and not vice-versa?

[carlosfloresmartinez]

Thank You so much for the information! ❤

[yubinator]

I like the n-channel mosfet version since n-channels are the most common mosfets. Some reccomend a mosfet driver if it ever be used on the high(?) side

[boopathimanikandan]

When we using MOSFET for reverse polarity protection, we need to use it for low ampere application. Because when MOSFET is used for DC current, we violating the SOA. For DC current, mosfet will generate lot heat than mosfet used in switching applications. Also from datasheet, 10 to 15% of Id(drain current) will be used to DC application. Its from my experience. Correct me if i am wrong. Also any experts design, pls provide details of selecting mosfet for DC current for 50A DC.

[Shrek_Holmes]

the best way is the P-Channel mosfet because it will disconnect the live voltage side and not ground, so the rest of circuitry beyond it is not live, however in the N channel method, the rest of circuit is actually live it's just that there is no ground path. I wouldn't really consider the other methods at all unless you have size constraints or very very low power and don't mind the voltage drop.

[louisbrown]

What about using a full bridge rectifier for a dc input so that it can also flip to polarity no matter what ?

[johansvideor]

"Canal" or "kanal" is the name for "channel" such as P-channel Mosfet in most western European languages other than English. Including Germanic, Romance and Slavic languages. They don't generally have the word channel, but use canal/kanal instead. Both channel and canal are from Latin and means the same, but in English they are used a bit differently.

[vickykhan]

Zack sir for polarity identification supposed in the Gerber silkscreen layer is not given, we don't have assembly drawing, we don't have a schematic .can we find the polarity any rule by using track or by decoupling capacitors or near components are placed near to ic.any method to find the polarity of ic without data like assembly drawing, schematic diagram, silkscreen not given in the Gerber .

[robertbox]

No mention of using n-channel MOSFETs in the positive side with a gate controller? These are common in automotive as you can easily add isolation with a 2nf FET and n-channel devices are cheaper and better than p.

[Freakingsstein]

I personally use the P-Channel MOSFET almost all the time.
What I don't like with the N-MOSFET option is that it introduces a voltage difference between the circuit GND and the real GND.
I am not sure if that in reality makes a difference, but IMHO this is a headache that I want to avoid.

[ugurkeles]

Hey Zach, I have done research before about the P channel MOSFET type but couldn’t get any information why there would be a resistor. I know diode clamps the voltage for MOSFET but resistor is not explained. Is it for limiting the leakage current? If so, is the leakage current that high to be limited by a resistor? Also, I have seen values such as 1K, 10K, or 100K for the resistor. How do you calculate these values?