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I'm creating an adapter which hosts two connector types and simply routes two connections from one connector into the other.

  • Only two traces/connections are used; Vcc (about 6v) and GND
  • Operating current is up to 1A max
  • Power is DC only, no signals

So my design uses only one "trace", which is for Vcc, while the ground simply uses the entire ground plane, which fills everything on the PCB other than the Vcc trace, as the return path. Both connectors have pins mounted to the ground plane, so it seems to me like it'll be fine (if not best) to just use the ground plane as the return path instead of creating a trace for it which connects to the ground plane at some point anyway. I've never seen a board use a ground plane as the "primary" return path (with no dedicated trace), though, and I'd like to confirm that this isn't some soft of bad design practice.

enter image description here

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  • \$\begingroup\$ Looks ok for me. I will wait for experts to comment though \$\endgroup\$
    – User323693
    Jan 25, 2017 at 13:17
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    \$\begingroup\$ Yes. It's not quite ideal because the VCC track and connector pads nearly cut the ground plane in two. If you could beef up the narrow neck there I would suggest doing so - maybe reduce the width of those thermal relief cuts. But if those 4 pads at the corners of the RH connector are just mounting, and carry no current, then it's fine as it is. \$\endgroup\$
    – user16324
    Jan 25, 2017 at 13:24
  • \$\begingroup\$ A good question with a simple answer. \$\endgroup\$
    – pipe
    Jan 25, 2017 at 13:53
  • \$\begingroup\$ @Brian Drummond, those 4 pads are indeed for mounting and not necessary for grounding. Good point about cutting the plane in two; I overlooked that, though in this case I don't expect it to be a problem as you said. Thanks for the input! \$\endgroup\$
    – Ed Sawden
    Jan 25, 2017 at 14:43

1 Answer 1

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Can a ground plane be used as a current return path?

The major benefit for using ground planes is that they are used for this very reason.

For instance, any circuit using a "perfect" ground plane guarantees that the local return path of current is directly beneath the forward (non ground) current flow: -

enter image description here

The bottom-line is that current takes the path of least resistance and, for AC currents, the path of least resistance is the path of least inductance.

In your situation any current that returns through the ground plane, flows close to the forward current path. This minimizes loop inductance, thus minimizes generated interference and received susceptibility to interference.

It's just what happens when you use a ground plane - instantly EMI problems are reduced by a large factor.

As mentioned in the picture, it's an example of proximity effect: -

enter image description here

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