Hi guys.
I'm trying to design and understand how to make my first 4-layer PCB.
I was thinking of using this as a starting stackup:

· Signal
· Ground
· Power
· Ground

The PCB will be a small motor and inductor controller with a maximum load of about 2A, but it will also have I2C, SPI, and I2S digital signals, so there will also be analog signals.
However, I'm doubtful about the top layout, as the power plane is usually an inner layer, which limits heat dissipation, and I would like to have the power on the top layer. Is it possible to divide the PCB in two in this way: ¾ reserved for control signals divided into the 4 layers as described above (SIG/GND – PWR/GND) and the other ¼ into two layers. Top layer for 12V power and button layer for a dedicated ground plane? Any advice on this?
Regarding the ground planes, is it advisable to divide the 3 maximum ones distinctly, PGND, DGND, and AGND Or is it sufficient to have the maximum power and digital together and another ground reserved for analog signals?

 

You don't need two ground planes. Keep in mind also that the power plane also serves as ground plane to AC.
Here is a typical 4-layer PCB stackup.
1 - Signal
2 - Power
3 - GND
4 - Signal

Reference: https://www.allaboutcircuits.com/technical-articles/common-layer-stack-ups-for-a-four-layer-board/

 

All of the above as needed. Impossible to say exactly say without knowing the exact component physical placement, signal speed, physical size and grouping. The most important thing is the electromagnetic path separation of motor/inductor controller energy paths (power and I/O connections) from the conventional digital/analog circuit paths.
https://resources.pcb.cadence.com/blog/best-formats-for-4-layer-pcb-stackups
Best Formats for 4-Layer PCB Stackups

I normally use a hybrid of various stacks on one board, depending what's (3.3v controller and circuits or higher power MC parts and paths) on that part of the board with layer 2 being the common GND plane. The stacks are suggestions for starting points, not edicts of actual PCB design and construction.

 

@nsaspook

What is the function of the attached PCB board?

 

@nsaspook

What is the function of the attached PCB board?

Universal Motor controller and Power inverter. A Software Defined 200W power supply/motor controller.

https://github.com/nsaspook/vcan/blob/i400_mcm/MC33932.pdf
https://github.com/nsaspook/vcan/tree/em540_modbus



https://forum.allaboutcircuits.com/threads/pic32mk-mc-qei-example.150351/post-1529419

The controller FOSC is 120MHz but actually more important here is the hardware double precision floating point co-processor and several 32-bit QEI encoder interfaces with rs485 and rs232 serial interfaces for external logging and control.

The PCB has four H-bridges that can be configured in many different ways. One of the pictured testing configurations was the one DC motor per H-bridge (three used with one extra), the other pictured configuration is a three phase motor setup with a H-bridge per phase (3 used with one extra)

400Hz 3-phase inverter

https://forum.allaboutcircuits.com/...r-for-3-phase-115v-supply.181424/post-1665711

400Hz syncro quadrature motor driver configuration.
https://forum.allaboutcircuits.com/...drature-phase-400hz-motor.187708/post-1746642