I'm making a pcb, and I wanted to ask people with more knowledge:
It is a good idea to have a ground plane on one side of the PCB going to batt - and a positive ground plane on the other side of the pcb?

I cant recall ever seeing this done and I'm wondering if I just haven't seen enough PCB's or if there is a valid reason not to do it?

The application is a dc motor controller working at around 25khz.

 

There is no right or wrong answer. It really depends on the application. The reason for requiring a ground plane is if you have a very high frequency analog circuit and you want to reduce the noise level in order to improve performance.

A more important reason for a ground plane, especially if you are going to etch the board yourself, is to minimize the amount of copper you have to etch. For a simple layout, one would choose a single sided copper clad board and use lots of fill or pour on the copper side.

If you must choose a double sided board, you may choose to move the ground to the bottom layer but still use copper fill on the component side.

Or you can run traces on both sides, but again, use lots of copper fill/pour.

(Of course, the other reason for moving to a double sided board is in a complex layout situation where you just cannot get all the traces in on one side without using too many jumpers.)

 

I would perhaps in this case tend more towards a star ground concept. Run the separate cables for the motor and control logic power. And split them at the power power supply. Use a CLC (phi) filter at the control logic positive voltage input.
You give very few details on your setup. And that makes it hard to give a good answer. In this game you can hardly give to much details. So just pour on details in you r first post. Like all about current and voltage specs.
In any case feel free to post your PCB here for comments.

 

One really good reason for having power/ground planes is the reduction of parasitic inductance.

Long, thin traces will have a significant amount of inductance. An infinite plane of copper has practically no inductance. Having power planes on a circuit board is somewhere in between the two.

 

Thanks for the responses guys, I just wasn't sure if it was the done thing...

I ended up putting multiple ground planes on the board. I need to get some boards made to test with, so it'll be interesting to see how it all works.