The device uses two separate power supplies: AVDD and DVDD. The internal circuits of the device operate on AVDD; DVDD is used for the digital interface. AVDD and DVDD can be independently set to any value within the permissible range.

The AVDD supply pins must be decoupled with AGND by using a minimum 10-µF and 1-µF capacitor on each supply. Place the 1-µF capacitor as close to the supply pins as possible. Place a minimum 10-µF decoupling capacitor very close to the DVDD supply to provide the high-frequency digital switching current. The effect of using the decoupling capacitor is illustrated in the difference between the power-supply rejection ratio (PSRR) performance of the device. Figure 126 shows the PSRR of the device without using a decoupling capacitor. The PSRR improves when the decoupling capacitors are used, as shown in Figure 127.

Code output near 32,769

Figure 126. PSRR Without a Decoupling Capacitor

Code output near 32,768

Figure 127. PSRR With a Decoupling Capacitor