Yes, differential. However, we're using edge-coupled pairs, and it's my
understanding, though I've done no analysis, that about 10% - 15% is about
as much coupling as you can get between edge-coupled lines. Thus, there is
still a strong coupling between the trace and it's reference place.
Therefore, I suspect that there's non-ignorable amount of return current in
the reference planes. I'd be interested to see a
return-current-distribution plot for a diff pair both in the reference
planes and the coupled traces.
Eric Goodill Cisco Systems M/S SJ-N2 mailto:email@example.com 170 W Tasman Dr voice: (408) 527-3460 San Jose CA 95134-1706 fax: (408) 527-3460 (yes, the same)
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