GND PLANE UNDER DC to DC CONVERTOR

[tiwari.sachin]

I am using a 4 layer board.

L1: SIGNAL
L2: PWR
L3: GND
L4: SIGNAL

I have a DC to DC Converter on L4 and inductor concerned on L1.

On power plane I am removing the complete etch under the converter.

Should I also remove the GND or stitch the same with vias??

And what if I stitch too and wouldnt that be a return path for DC to DC and that noise has effect on other grounds


If I have a separate power ground plane beneath DC to DC and connect that ground to other digital gnd plane via one or two point connection. Is that a good option

 

[FvM]

On power plane I am removing the complete etch under the converter.

Should I also remove the GND or stitch the same with vias??

Trying to achieve what?

I don't think that the questions can be answered without knowing the circuit details and implemented ground scheme.

I would generally try to keep ground planes continuous, unless the power inductor has an air gap and a respective strong stray field on the bottom side.

It may be appropriate to isolate the commutating current loop, possibly also the first (inner) stage of converter input/output filters from the common ground plane, implementing a local converter power ground, possibly using a small regional plane on L2 with a one-point connection to the global GND plane.

 

[tiwari.sachin]

This is a second proto board. I tried achieving using 2 layer board and saw a lot of ringing. This probably was because the placement and routing was not proper.

I am now using the 4 layer design hoping to minimise the same.

Should i have a global ground connected beneath DC 2 DC and connect it to remaining ground via single point.

 

[FvM]

For standard requirements, it's probably better to use the global ground plane also for the internal DC/DC converter nodes.

The mentioned local DC/DC converter power ground is an option for low noise design. But it can go wrong if you don't consider everything well, and it doesn't have much effect without additional input and output filters for the converter.

A continuous ground plane can be expected to bring large improvements for your design, I suggest to evaluate this technique and proceed step by step.

 

[marce]

The best option for switching convertors is to ensure that the switching loop return (Cin, Coutany Diodes etc.) is a separate copper pour on the same layer as the components and is joined to the main ground by a cluster of via's at one point.
What controller IC are you using?
Have you found any layout guidelines or example PCB design for said controller.

 

[tiwari.sachin]

I did find some layout on datasheets. I have followed the same and designed the board.

I am awaiting for the PCBs and I am really looking forward to see the results