Re: [SI-LIST] : Differential pairs and place splits

D. C. Sessions (
Wed, 11 Feb 1998 08:32:15 -0700

Young, Randy wrote:

> I understand that in general, routing high-speed digital traces across
> plane splits is a bad idea from both a signal quality perspective and an
> EMI perspective due to return current paths. My question is concerning
> differential pairs - specifically, USB and 1394. Do the same rules
> apply? Is routing a differential pair across a plane split bad from
> either signal quality or EMI perspective? My assumption is that the
> return current path for a differential pair is the other trace of the
> pair, and that this would greatly reduce any signal quality or EMI
> problems associated with crossing splits. Is this correct?

In addition to what others have written (wrt symmetrical current
paths and CM currents) please note that USB, at least, is
intentionally so slow that most of these issues are moot.

D. C. Sessions