ADUCM360/361: ADC ENOB Calculation

Q

In the ADuCM360/361 datasheet - how is the ADC Effective number of bits figure
calculated
from the noise tables?

A

The RMS noise is derived by taking 200 ADC conversion results with an internal
short selected as the ADC input (Same Ain channel selected as the positive and
negative input to the ADC).
The RMS Effective Number of bits is calculated as follows:

            RMS ENOB = log10 (Voltage span/RMS noise)
            _________________________________________

                           log10(2)

The voltage span is 2x VREF when 2's complement ADC output results are selected
via ADCxCON[18]. (Bipolar ADC readings)

     Pk-Pk ENOB = log10 (Voltage span/Pk-Pk noise) where pk-pk noise = RMS
noise x 6.6
                         ________________________________

                                     log10(2)