Should I Separate Analog vs. Digital Grounds in a PCB Design?

In circuit designs, the topic of separating ground planes has divided engineers for years. Do I split or not split the ground plane into analog and digital planes? 

Ground planes are used to provide a low-impedance path for the return current of signals. In general, we are prone to categorize these returns into two key types: analog and digital returns. Should these be kept separate?  

Digital return planes are intended for clocked circuitry which includes microprocessors, memory, and other digital logic circuits. These circuits require a ground plane that can handle high frequency switching and the associated transient currents. Analog return planes are often intended for elements such as sensors, amplifiers, and filters. These analog signals have less tolerance for voltage-value fluctuation. Historically, this was achieved by creating a separate analog ground plane isolated from the digital one. It was assumed that the return current of the higher-frequency digital signals would induce noise and interference, impacting the analog values. 

If analog and digital circuits are operating together as one system, their grounds must be connected at some stage to synchronize the base reference. What if there are multiple analog and digital circuits with multiple grounds? In the past, a single connection point was advised, referred to as a "star ground" or "ground node". The idea was to prevent ground loops because multiple ground loops can also induce noise and affect performance. So, this is how it was done. 

However, these days, there are numerous signal-integrity experts who say that we should never split ground planes. They strongly advise that this introduces more problems than it eliminates. Doing so introduces a negative effect due to discontinuous ground return paths of transient currents and their fields. Continuity for these electromagnetic fields is the key, and we should not create obstacles for these fields. 

So, should we separate ground planes sometimes, and if so, when?  

What are the factors that affect your decision to do so? 

Should we connect all grounds immediately to a single plane or isolate portions of the circuit into separate planes, connecting only at a star point? Any experience you could share would be appreciated so that we all might grow our knowledge and improve our design skills.