Power and Ground plane in PCB Design?

Thread Starter

Aashram

Joined Nov 17, 2014
10
Hello,
I am making a 4-Layer PCB.
When I made 2 layer PCB, I put GND plane on Top and bottom layer. But when I am doing 4 layer I have top, bottom, GND and power layer. But I do not know what should I do with the GND and power layer. Do I still have to do GND plane on top and bottom layer?
What is the GND and Power plane for?
Should I make three GND plane: 1 on Top, 2. Bottom and 3. On GND layer?
I am confused?
And what do I do with power plane?
 

dendad

Joined Feb 20, 2016
3,251
I have top layer, then power plane, ground plane then bottom layer.
This way the top and bottom layers are shielded from each other and you can get to the tracks for mods or debugging. Using separate power and ground planed lets you keep the max amount of copper for lower impedance runs, improved bypassing as the planes make a capacitor and also can make it easier to lay out as you have more room for the tracks and just need to include a power/ground via for connection.
 

Thread Starter

Aashram

Joined Nov 17, 2014
10
Thanks,
I have two different voltage in this design. (3,3 and 5 Volts). The Power plane should be having the voltages or something else?
 

kubeek

Joined Sep 20, 2005
5,655
That depends on your circuit. Sure, four layers give you a better layout and performance, but does your circuit really justify the almost double price for the pcb? Maybe if you show what you are doing, you would get better advice.
 

dendad

Joined Feb 20, 2016
3,251
Here is an example of a ground plane of from one of my boards...
gndplane.jpg
You can see the ground plane is split into 3 parts that join in one place. This is to keep the 2 motor currents away from the analog input currents.

And in the power plane...
pwrplane.jpg
There are a number of separate power feeds, like 24V in, 5V, 24V to motors...
Having a ground and power plane does make it easier to run the tracks where you want them, but if you do what I did, and have an artwork error, it can be a new board to fix it!
 
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