SAADC external voltage reference

[pazcal]

Hi, 

The Ai0, and Ai1 inputs can be used as voltage references for COMP feature. Is there a way to use input Ai0/Ai1 as reference voltage for SAADC?

Thanks in advance

Regards

Pascal

[Kenneth]

Hi,

You can almost do what you want, but you need to sample both the analog input and analog reference using two analog inputs (e.g. AIN0 and AIN1) using the internal reference first. Assume the following measurements and calculation:

Measure: Analog_in_signal(AIN0) = your_input* gain/internal_ref
Measure: Analog_in_reference(AIN1) = your_reference * gain/internal_ref

Calculate: Din_scaled = Analog_in_signal(AIN0) / Analog_in_reference(AIN1) = your_input / your_reference

Din_scaled is then basically the measurement you then want.

Best regards,
Kenneth

[pazcal]

Hi Kenneth, 

Thanks for your fast feedback.

My initial question was to use Ai0/Ai1 as standard Vref for the SAR, instead of the internal 0.6VDC, or VDD. But the proposed option will do the job as well. thanks a lot

regards

Pascal