Splitting voltage of Power Supplies and Grounds in double side PCB

[cefreyle]

Hi everyone.
I write hereby to ask you about splitting voltages and grounds in a double side PCB that I am designing. A colleague at work has adviced me to split the 5V and 3.3V in digital, RF and analog traces as well as the grounds ( I have uCs, opamps and communication modules). He says he has seen it in a Application Note somewhere but he haven't it. I have done and initial separation of the power electronic circuits (+24V, +12V) and now for the rest of circuits I don't have too much space for the traces (The size of the pcb is fixed), so I am struggling with it. I consider it would be necessary to split the ground for each voltage (because of the returning currents) and that seems enough for me. What could you suggest me? Have you any tips to route the voltage supply lines in a double side PCB?
Thank you in advance

[robertferanec]

This is not easy to answer: 2 layer PCB with digital, RF, analogue, .... and to really much information.

What I would be careful about, would be power filtering - good filtering of communication module power, good filtering of Digital power and good filtering of analogue power (means inductors, capacitors, beads etc - I do not know the exact values, you would need to google for more information about filters or ... put there footprints and the exact values you would choose during testing). I do not necessary split grounds (often I use solid ground plane - which you can not use in 2 layer PCB), however if analogue part is too sensitive I may design the analogue part as a completely separated part of PCB (it would be almost like a second board but placed on the same PCB with other circuits).