ADC Differential Inputs

[Amir1]

Hello Community,

Suppose that an ADC is configured to receive a differential input, say PA0 and PA1 as the non-inverting and inverting inputs respectively. Does that mean that the ADC reading can now be a negative number (corresponding to a a negative differential input voltage)? I know that no input voltage can be negative, but how about the differential voltage? What will be the digital reading if the differential input is negative, that is, if PA0<PA1?

My sense is that the differential feature is applicable only to improve the resolution, but is really not to capture negative analog voltage differentials. Correct me if I am wrong.

Amir

[SFeje]

Hi!

I also try to figure out the differential ADC. I think, that it should work like: 0 to refVoltage.

Im my case, I have 1.5V middle value for both channels.

On change: PA0 -> 0 and simultaneously PA1->3V.

And then the value first time PA1-PA0 = 0, and after PA1-PA0 = differential;

But i can't handle that like this.

Fejes

[Uwe Bonnes]

You can capture a negative differential voltage and differential ADC range is +/- VREF, but the absolute voltage at the input pins must stay in the common mode range (0 to VDDA).

[S.Ma]

Single channel measurement means differential with second channel grounded, hence is positive.

In true dual channel differential, yes you should be able to measure positive and negative values.

You can play with the pins pull-up and pull-down to test 3.3V <=> 0V, then swap for 0V <=> 3.3V

Differential mode if typically used to remove common mode noise and typically used in a sensor using wheatstone bridge