I want to build ECG (electrocardiograph) circuit using your ADC AD7172. It has separate power inputs for analog circuit (AVCC, AGND) and for digital (SPI communication) circuit (DVCC, DGND). I am planning to use two completely separate power sources (Li Ion 18650 batteries) for analog (ADC & signal amplifiers) and digital (ADC & microcontroller & Bluetooth) circuits.
Do I need to connect the ground circuits of analog and digital circuits? I do not want to connect it due to high noises in digital circuit.
Please response me asap, so I can make myself proper PCB and start prototyping.