Schottky diode for analog input protection

Looking for a good Schottky diode for protection of analog input (A0, A1,...), The source of analog signal that i use can reach high voltages and has the potential to damage the analog input.
The Schottky diode has the ability to rectify such signal when reaching high voltage above certain value, while keeping high response time.
I wonder which diode model fits for this kind of purpose?

FYI

Any off the shelf Schottky diode should suffice.

I’ve used 1N5819.

I looked in to it, according to the datasheet the diode 1N5819 works with voltages in the range of above 10 Volts, it looks like more then what the arduino inputs can resist.
Or am i missing some important details?
The rectifying depends on the voltage that is applied on the diode?
In that case, i can really use any diode for this purpose.
Please correct me of i'm wrong here

Suggest "clamp" in lieu of "rectify". For uC analog, the rectification is a different subject. Agree the two are tightly interwoven with HV AC signals to single-ended analog on Arduino.

You would be using them as a clamp.

image

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Layered defense, I like it!

I checked around a lot and came up with this for protecting my analog inputs.
The cap can be changed to suit your noise immunity/time constant requirements.
The diodes are 1N5819
The voltage divider would need to be adjusted to suit your application.

An external 5v regulated supply is used for sensors and devices, NOT the Arduinos own supply. This eliminates much of the issues with excessive voltages (or shorts) feeding back into the 5v arduino supply and burning out internal components.

image

Here's a good source:

I calculate that you want to measure to 18.75volt. Car battery?

If that analogue voltage is really a voltage (not a ratiometric sensor),
then you should use a voltage divider to 1volt and switch to 1.1volt Aref (code).

With that, and resistors increased to 150k:10k (0-17volt) or 180k:10k (0-20volt), the pin will stay below 5volt to input voltages >80volt before the internal clamping takes over.

With the above, and a 100n cap from pin to ground, you won't need external diodes.
Leo..

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An advantage of using the 1.1v reference is that the input is still protected to 5v .

So if your scaling resistors gave you a full scale voltage of 12v , the input is protected , as is , to around 60volts .

Thanks for the idea Wawa, simplified is often better. I'll see how that fits in with other things I have to measure.

Aref can be switched in loop() between default and 1v1.
Leo..

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