General • Re: ADC creapage on the RP235X

Repeat the test with a resistive divider on Vref feeding the ADC input pin.

I'd rather get to the bottom of this mystery as it is. I don't really care if the issue goes away under other circumstances, I would like to know why it exists for what I have.

Also, at least for the RP2040 the issue also exists when reading the temperature sensor.

What would be the utility of reading a floating input?

None. It's simply curiosity why it happens in this mode, which seems to parallel the RP2040 behaviour, and when reading its temperature sensor.

Also, as I said, I have never observed this behaviour with any other ADC I have used.

The charge creepage will be through the PCB and through the substrate of the die. You need to have some resistance to ground to discharge this charge building up on the stray capacitance on the ADC input pins.

But do you have any explanation of why there is only creepage when the interval is 13 minutes or more, why it's never seen with anything less ?

Would anyone say that what I am seeing is "as expected" and can actually explain why it's to be expected, why it only manifests with 13 minutes or longer intervals between ADC reads ?

Statistics: Posted by hippy — Thu Nov 21, 2024 3:33 am

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