I need to implement the ADC chip MCP3004 in a circuit. The Vref and Vdd are tied to 3V3 rail. According to datasheet of this ic the maximum voltage that an ADC input pin can handle is Vref, so in this case is 3V3.

Because of some things, voltage on any ADC input pin can go as high as 3.5V. Now, according to datasheet of the device on the "Absolute Maximum Ratings" it is stated that:

All Inputs and Outputs w.r.t. VSS ............– 0.6V to VDD + 0.6V

I understand that the variation of +-0.6V on input is related to protection series diodes that are tied to the input pin. So in this case the maximum positive voltage on input will be 3.9V and minimum will be -0.6V which it is on my specs.

My questions are:

  1. Will it be safe to apply 3.5V, for a small amount of time?

  2. What will be ADC output?

Thank you in advance for your answer.


1 Answer 1


Yes, it will be safe and, the digital output will be limited at full scale.

Also be aware that there are offset and gain errors in the ADC that will make the reliable range for extracting a meaningful digital value a few tens of milli volts within the nominal range of 0 volts to 3.3 volts i.e. you can’t rely on the full scale range being perfectly 3.3 volts.

  • \$\begingroup\$ Andy aka thanks a lot. \$\endgroup\$ Sep 21, 2019 at 10:44

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