Design Considerations for Upgrading to a 6-Layer PCB with Separate Analog and Digital Grounds

I am designing a sensor module using the AD5940 AD5940 Datasheet and Product Info | Analog Devices

I have designed a small module PCB using a 4-layer stack-up. However, after further reading, I understand that it is recommended to separate the analog and digital grounds. Therefore, I am considering upgrading to a 6-layer PCB. The additional layers would provide an extra GND plane and a signal layer, offering greater flexibility in signal routing.

I have a few questions regarding this:

Current 4-Layer Stack-Up
When using 4 layers, my stack-up is as follows:
- Top Layer: Signal
- 2nd Layer: GND
- 3rd Layer: VCC
- Bottom Layer: Signal

Questions

1. Placement of Additional Layers:
With a 6-layer stack-up, where should the additional two layers (the second GND and signal layers) be positioned?

2. Connecting Analog and Digital Ground:
My PCB module has a connector where the VCC and GND enter the circuit. Should the digital and analogue ground planes meet at this entry point?

3. Copper Pour and Via Stitching:

On my signal layers, I typically use a copper pour connected to the GND net via stitching to connect to the GND layer. With the introduction of two separate GND planes (analogue and digital), how should I handle the GND nets?
- Which GND net should be used for the copper pour on signal layers?
- Should via stitching be avoided to prevent reducing copper coverage on the respective GND planes?

4. Best Practices:
What is the best approach for managing the analogue and digital GND separation in a 6-layer PCB?

Looking forward to your insights and recommendations.