[SI-LIST] Guard traces for differetial pairs

Gurus,

Could you pls make comment on below statement on guard traces for
differential pairs?

Use gnd traces as guard trace is not very effective if there is gnd =
plane
direct underneath the differential pairs. As the current is mostly going
through the plane (lower impedence path), there will be no (or little)
current in the guard traces. When there are not current in the guard =
traces,
the guard traces will only shield electrical field but not magnatic =
field.
So magnatic coupling will not be better with the gnd guard traces.

Thanks


Tonglong Zhang=20
Staff Engineer=20
IC Packaging Engineering=20
Broadcom  Corporation=20








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