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ADC Input protection in K22 series

Question asked by Nicolas Giussani on Dec 21, 2016
Latest reply on Jan 2, 2017 by Nicolas Giussani

Hi,

 

First of all, I'd been digging around the community and found no specific answer for my concern, so I'm afraid I have to ask for some help.

 

I'm implementing an application around a K22 series microcontroller (most likely the MK22FN128VLL10) We are trying to cut down parts, due to space/cost requirements. One of the most repeated circuits and most space consumming is the precission voltage clamping for the ADC input protection, so that's where we're aiming right now.

 

We are using 3.3V supply and 2.5V VREF, and we are not completely sure about the protection needed. It appears, form the datasheet, that we may have to clamp to VREFH to protect the input (despite the internal protections) and this may not be easy as we are using a voltage reference and not one with great source/sink capabilities. We are trying to implement a simple diode clamping scheme and doing so will end in either 3.3V + Vf or 2.5V + Vf on the input.

 

The main answer we are looking for: exceding this limit in an input is destructive or will only affect meassures?

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