I am about to design my first PCB as part of my graduation project. Of course, as the first step, I try to learn as much as possible. A part of the research I found this 3 part article, that suggests that it is not neccessary and in some cases is even harmful to split the ground plane into analog and digital part, which contradicts what I had learned from the prof. I also read all threads on this site that are concerned with the ground planes/pours. Although majority concur with the article, there are still some opinions that advocate split ground plane. eg
As a PCB design novice, I find it confusing and hard to decide who is right and which approach to take. So, should I divide the ground plane into analog and digital parts? I mean physical division, either with a PCB cut or having separate polygons for DGND and AGND (either not connected, or connected in one point)
Perhaps to enable you to make a recommendation, that is tailored to my prospective PCB, I tell you about it.
The PCB will be designed in the free version of Eagle=> 2 layers
The PCB is for testing and precise measurement (current & voltage) of lithium batteries. The board is to be controled from Raspberry Pi over digital interface (GPIO/SPI (40 kHz)). There will be 3 data converters on board (AD5684R, MAX5318, AD7175-2),and connectors for a prebuilt RTC module on the digital side. Analog power comes from external regulated power supply over onboard LT3042 voltage regulator (5.49 V). Additionally there is LT6655B 5 V voltage reference. Analogue part is essentially a DC circuit, the only really HF is internal 16 MHz master clock of the ADC.
Digital 3.3 V (mainly for powering of the digital interfaces) will be sourced from Raspberry PI. Thus, there will be 2 ground connection: external power supply and to digital interface of Raspberry Pi.
In this connection another question: referring to Figure 3, how do I make sure that return currents from the digital interfaces flow to the right ground connection (remember I have 2 of them)?
Additional concern: could the power distribution curcuit disturb sensitive measurements? I was going separate them by routing power on the bottom layer, but that is no longer a good idea in case of monolithic ground plane
And while I am still at asking: Assuming more or less monolithic ground plane on the bottom and signal/component layer on top, what is the best way to connect the negative side of bypass capacitors to the ground plane?