The devices have two separate power supplies: AVDD and DVDD. The device operates on AVDD; DVDD is used for the interface circuits. AVDD and DVDD can be independently set to any value within the permissible ranges.
When using the device with 2 × VREF input range (CFR.B9 = 1), the AVDD supply voltage value defines the permissible voltage swing on the analog input pins. To avoid saturation of output codes, and to use the full dynamic range on the analog input pins, AVDD must be set as shown in Equation 9, Equation 10, and Equation 11:
Decouple the AVDD and DVDD pins with the GND pin using individual 10-µF decoupling capacitors, as shown in Figure 116.