Can anyone outline the advantages and disadvantages of using broadside
coupled
vs. edge coupled differential traces?
>Broadside Coupled yields a lowed Zdiff than edge coupled (given the same
dielectrics).
BS coupled pairs need to be on the same core to control front to back reg
better.
If not, the cumulative tolerances can yield a large difference. Also keep in
mind
that small linewidths may also be the same as your lyr-to-lyr registration
overall and
will be very difficult to maintain the BS coupling. Most equations and
software
I've tried are not too accurate for BS coupled stuff. Usable but not to
accurate
(compared to edge coupled).

Is either one better from a signal integrity perspective ( less lossy?
lower crosstalk?).
>Edge coupled may have orthogonal cross overs if dual stripline is used.
However keep in mind that the pairs behave like twisted pair which has a
reduced (better) noise immunity. BS probably would only have it's pairs
together
with no crossovers.

Is it easier to route broadside coupled traces in high density applications?

>This I don't know. (Sorry)

Edge Coupled has less cumulative tolerances to watch out for. Hence easier
to
maintain the Zdiff results. The only real advantage I've seen for BS is for
large extender cards or hugh linewidths (Let's leave that 28 Ohm stuff out
of
this conversation).

Groovy

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