PCB grounding issues

[dm927]

Hello,

My group is working on putting a power inverter on PCB board. While the circuits are connected to seperate grounds (on breadboards), each circuit works properly. However, when all of the grounds are connected to the same point, some of the circuits don't work properly. How can we fix this grounding issue?

 

[John Sorensen]

You're going to have to give more details. You can find good information (App Notes) on most IC mfr's websites about good PCB design. Atmel and Intel both do, for sure, and I'm pretty sure Zilog and National do, too.

j.

 

[ChrisP]

As I replied in that other forum ...

Do the "separate" grounds on the breadboard tie back to a common point somewhere? Or are they maybe from two different supplies?

It almost sounds like the "grounds" aren't at the same potential, and that tying them together is causing the problem...

 

[dm927]

Everything is powered from a single supply.

 

[Optikon]

Everything is powered from a single supply.

Thats doesnt mean the "grounds" are at the same potential.
Remember, the trace that is "ground" that runs in some fashion across the board, has resistance, and parasitic capacitance and inductance associated with it. Long wires that connect board grounds together that have current flowing in them create nice big parasitic inductances (if the path has a large loop area)

If you power inverter has a switching circuit, like a push-pull or buck/boost in it, switching currents may be going where you dont want them to causing problems - especially if they are forced to take inductive paths. Try and post your circuit, the root cause of your problem might be layout related.