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

Mike Jenkins (jenkins@lsil.com)
Tue, 10 Feb 1998 19:08:54 -0800

Vinu Arumugham wrote:
>
> It depends on the amount of coupling between the differential pairs. In
> many implementations of differential pair traces, there is a tighter
> coupling to the reference plane than between the traces. Since the bulk of
> the return current would flow through the lowest impedance path ( in this
> case the plane ), a split in the plane would remain a signal quality and
> EMI concern.
>
> Vinu
>

Vinu,

Even if the ground plane carried significant return current, these
currents
are equal and opposite for the pair. Encountering a split plane causes
the
return current for one line simply to do a U-turn, becoming the return
current for the other line. On the other side of the split, the same
thing
happens. The discontinuity is still MUCH less than for a single-ended
line.

Mike

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