SBAS825 April 2017 ADS8578S
The ADS8578S uses two separate power supplies: AVDD and DVDD. The AVDD supply provides power to the ADC and internal circuits, and DVDD is used for the digital interface. AVDD and DVDD can be set independently to voltages within the permissible range.
The AVDD supply can be set in the range of 4.75 V to 5.25 V. A low-noise, linear regulator is recommended to generate the analog supply voltage. The device has four AVDD pins. Each AVDD pin must be decoupled with respect to AGND using a 1-µF capacitor. Place the 1-µF capacitor as close to the supply pins as possible.
The DVDD supply is used to drive the digital I/O buffers and can be set in the range of 2.3 V to a maximum value equal to the AVDD voltage. This range allows the device to interface with most state-of-the-art processors and controllers. Place a 1-µF (minimum 100-nF) decoupling capacitor in close proximity to the DVDD supply to provide the high-frequency digital switching current.
There are no specific requirements with regard to the power-supply sequencing of the device. However, issue a reset after the supplies are powered up and are stable to ensure the device is properly configured.
Figure 88 shows a typical PSRR curve with the decoupling capacitors.