Differential ADC output

[Barata]

Hi

Why does making an input differential lose a bit on the nRF52. According to the data sheet, if a channel is 10 bit and using 0.6V reference and gain 1 and input is 100mV differential, then the output will be:

0.1 * 1 / 0.6 * 512 = 85

Where as if it is 100mV single ended the output is:

0.1 * 1 / 0.6 * 1024 = 171

Is this correct?

Just to clarify. When the input is differential, lets say the positive input is 300mV and the negative input is 200mV.

Also if the inputs are differential and 1.5V and 1.4V, on a 3.3V supply, will the differential input still work with a gain of 1 and reference of 0.6V and will it give the same answer?

Thanks again.

[Barata]

Probably because in differential mode the result is signed.

But that doesn't explain why some people are reporting negative values in Single Ended mode due to miss calibration. I don't know what this means.

[run_ar]

More details on negative values in single ended mode here.