AD7177-2 PCB Layout Recommendation

Hello everyone,

I am currently working on my first mixed-signal pcb project. I will be using the ADXL354 as my sensor and the AD7177-2 as my ADC. I plan to use separate ground planes for my digital and analog circuits.

Based on this article ( the ADCs and DACs (and other mixed-signal ICs) with low digital currents should generally be treated as analog components and also grounded and decoupled to the analog ground plane.

1. How will I know if my ADC of choice have low digital current?

2. What should be the current range of an ADC for it to be considered low digital current?

3. Does the statement above applies to the AD7177-2? If yes, what pins of the AD7177 should be connected to or decoupled to my digital ground plane?

4. In the schematics provided by ADI on their datasheets, what do these grounds symbols below refer to? (Chassis ground, analog ground, digital ground)?

Also for the ADXL354 sensor,

1. I have separate 3.3V supplies for my analog and digital circuits and separate ground planes for analog and digital circuits as well. If I connect my VDDIO to my dedicated 3.3V digital supply, should I decouple it to my digital ground plane and also connect the VSSIO to my digital ground plane? Similarly for the VSUPPLY if i connect it to my dedicated 3.3V analog supply, should I decouple it to my analog ground plane and also connect VSS to my analog ground plane? Would this setup improve noise immunity?

2. Or can i just connect VSSIO and VSS together and connect it my analog ground plane, connect VDDIO and VSUPPLY together and power it using my 3.3V analog supply and decouple these pins to my analog ground plane as well? Which setup is recommended?

revised questions
[edited by: nognog024 at 9:27 PM (GMT -4) on 19 Apr 2021]