I have a two layer PCB, where I do not have the liberty of adding power planes. (However, I potentially could add ground or power pours). My issue is that I am trying to decide whether I should use a strict star-topology to route power and ground to each IC, or also add additional ground return paths for the signaling between the ICs.
To illustrate my point:
In the picture, RED corresponds to the power traces, and black corresponds to the ground traces that are currently on the PCB. The gray traces (also highlighted by yellow) are the additional ground traces I am considering adding between the ICs to serve as return paths for the data signaling between the ICs (mainly i2c and spi).
I am torn between adding these additional traces because of the potential of creating a ground loop. However, I may also need to provide a return path for the data lines between the ICs.
What is better? How do I solve this problem of ground loops versus return paths?
As an additional question--while not ecnomocically feasibly, is it worthwhile to try to move to a 4-layer PCB? When do you determine whether you should move up to the 4 layer PCB?