SBAS991 February 2021 ADC3663
The ADC366x includes a digital channel averaging feature which enables improvement of the ADC dynamic range (see Figure 8-40). The same input signal is given to both ADC inputs externally and the output of the two ADCs is averaged internally. By averaging, uncorrelated noise (e.g. ADC thermal noise) improves 3-dB while correlated noise (e.g. jitter in the clock path, reference noise) is unaffected. Therefore the averaging gives close to 3-dB improvement at low input frequencies but less at high input frequencies where clock jitter dominates the SNR.
The output from the digital averaging block is given out on the digital outputs of channel A or alternatively can be routed to the digital decimation filters using the digital mux.