The AUX ADC path serves as a redundancy path to the Main ADC measurement on VS voltage measurements. It also has the front end filters of a BCI filter and an AAF filter in the AUX ADC path. The AUX channel are multiplexed (shown as the AUX MUX in Figure 8-5) to share a single BCI filter and AAF filter. The AUX MUX output after the front end filters is then going into one of the AUX ADC MUX and to the AUX ADC for measurement.

Because the front end filters are shared, the device has to wait for the AAF filter to settle before making any valid AUX channel measurement. The default AAF fcutoff is 1.6 kHz as in the Main ADC path, which translates to additional 4.3-ms settling time to complete a single AUX channel measurement. The device provides three AAF settling time options, 4.3 ms (default), 2.3 ms, and 1.3 ms, configured by the ADC_CONF1[AUX_SETTLE1:0] bits.