With the ADC using single ended input channel, what is the internal vref, what is the 12 bit voltage range for measurement (is it 0 to 2.5V or 0 to 3.3V)? What is the lowest accurate measurement resolution when we have less than 20mV to measure?

[PRedd.111]

I am trying to work with photo diodes and need to measure 20mV or less with ADC. Whats the best resolution I can get with a single ended ADC (using ADC 3 channel 12 at the moment).

Whats the measurement range on that channel? When we have less than 10mv, Is the ADC likely to give out a 0 value ?

[TDK]

Generally VREF is the same as your VDD voltage, which is usually 3 or 3.3v, but it can be lower. Resolution would be VREF/4095. So 0.8mV or so.

10mV should definitely return a nonzero reading for a 12bit sample. Readings near zero are a bit more stable than higher values, but your resolution will be limited.

[PRedd.111]

Looks like that 0.8mV is true. My VDD is 3.3V and my measurements seems to confirm the same. Thank you.