ADC question

[Yano]

Hi, are my assumptions below correct?

Measuring a (ratiometric to VCC) analog signal and selecting VDD_1_2_PS as the reference selecting AIN_NO_PS or AIN_2_3_PS will not be able to measure full scale.

Selecting AIN_1_3_PS with VDD_1_2_PS will give a lower resolution?

Is there any problem selecting AREF0 and attaching it to VCCthen selecting AIN_NO_PS? That way we have full resolution and don't need to worry about the 1.7V-2.6V to 2.5V-3.6V supply ranges (3V battery supply)? Thanks

[Stefan Birnir Sverrisson]

Hi

It is not possible to connect VCC directly to AREF0, because the voltage of the AREF0 signal must be in the range 0.83V-1.3V, see the nRF51822_PS v3.1 table 51.

If you have an analog input signal that is ratiometric to VCC and in the range 0V-VCC, then I suspect it is convenient to select VDD 1/3 PS reference and AIN 1/3 PS as the prescaler for the input signal.

If you select AIN 1/3 PS adn VDD 1/2 PS for input signal range of 0V-VCC, then you will not utilize the full resolution of the ADC, only 66% of it.