I am desigining a 4-layer PCB with the following stack-up: Signal Top, Ground Plane, Power Plane, Signal Bottom.
This is the first PCB I make like this, which includes a noisy SMPS with a switching frequency of 600KHz, as well as a 32MHz uC and a wireless 2.4GHz module. I wish to isolate the noise of the different blocks and prevent it from interfering in another block, for example, the SMPS and uC noises should not interfere with the wireless module. For that, I am splitting the power plane in three closed areas, one for each voltage (SMPS' generated 5.0V and 3.3V and 5.0V from a very small 50mA linear regulator for the auxiliary turn-on system), but keep the ground plane unsplitted and covering all of the board. The SMPS, the uC and the wireless module blocks are separated from each other's on the board.
The questions are:
- This split up arrangement would help from noise traveling between the modules?
- Would pouring up ground copper in the top and bottom sides help reduce EMI noise external to the board?
- Would be better to also split up the ground plane (and NO ground pouring on top and bottom sides to avoid a loop), and connect it in a star fashion? I heard that is better to keep the ground plane whole, but everyone seems to have his own version.
My understanding is that a ground place should always be below or above the signal and power traces to minimize loops and reduce EMI generated by the board. Also, IF the different blocks are already physically separated on the board, their return currents would flow in the unsplitted ground plane without interfering with each other. Is that correct? But I also read about splitting the ground plane into zones, one for each subsytem and connecting these different blocks in only one point (star connection). Which is better, and why?