What happens if VADIN > VREFH?

[zingere]

On the K60 datasheet it said VADIN should max out at VREF.

I have an analog input that can connect to different types of sensors external to the board. I want to have a reference voltage of 3.0V but also be able to clamp the analog input signal line to the 3.3V rail to not burn out the MCU pin in case of higher voltage being applied.

In my past experience with ADCs, if the analog signal went above the reference signal, it would just register as the max ADC value. Is that not the case here? Will having VADIN (3.3V) > VREFH(3.0V) cause damage? I don't know why any damage would happen to the pin if they are 3.3 or even 5V tolerant. The only issue i could think of is maybe reverse current flow somehow but I am not at all familiar with the internal circuity...

Also, what is the current draw of the VREFH? I cannot find it in the datasheet.

[miduo]

Hi,

Did you have noticed the errata e3863? I attached the errata below. I was thinking that this is one reason that K60 datasheet said VADIN should max out at VREF.

https://www.nxp.com/docs/en/errata/KINETIS_50MHZ_4N86B.pdf

As for the "damage", actually the capacitors in the ADC's internal DAC will be the weak point in the design as far as over-voltage is concerned. Looking into it a little more closely, it will be able to handle 4V. Where damage will start
to occur is a little harder to say, and we would need to get some more help to figure that out if needed.
 

 

[zingere]

I am going to clamp the signal at 3.3V so it will be ok.

Can you point out where I can find the current draw of the VREFH?

Thank you for your time!