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If I feed 2.5v to Vref pin on a MCU runs on 3.3v, what is the voltage for Voh?

I though Voh would be around 2.5v but I found the following table for the MCU(http://www.st.com/content/ccc/resource/technical/document/datasheet/03/b4/b2/36/4c/72/49/29/DM00071990.pdf/files/DM00071990.pdf/jcr:content/translations/en.DM00071990.pdf) enter image description here

looks like Voh has nothing to do with Vref, so I am confused.

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    \$\begingroup\$ why do you think it should do anything with Vref? Vref is for ADC. Vohis a parameter of the digital pins. \$\endgroup\$ – Eugene Sh. Aug 16 '17 at 17:16
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Vref is used to set the maximum voltage that the DAC analogue output can provide. It is also used to define the maximum input voltage when making analogue to digital conversions. It has nothing to do with logic levels CMOS, TTL or otherwise.

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  • \$\begingroup\$ I think Vref is for ADC, though got confused myself at first... Maybe for both, though. \$\endgroup\$ – Eugene Sh. Aug 16 '17 at 17:32
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Vref is the reference voltage for the internal ADC. If the ADC reads a maximum value from the input, then the voltage on the input is Vref or higher.

Voh has nothing to do with that, and will be close to VDD.

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