Electronics Forum / CAD / July 2007

Hello,

designing a motherboard featuring a Virtex-4 FX140 FPGA with 24 integrated
RocketIOs (Gigabit SerDes IOs) I am now facing the problem of how to get the
signals off the board in a most space-saving and elegant way?

All 24 differential signals will be connected to some DACs outside the
motherboard to convert the signals into the analog signal domain.

In the definition of the interface I have nearly all effective degrees of
freedom. I once learned that coaxial connections are the most appropriate
way to do so in terms of signal integrity, but with 24 differential signals
and bidirectional connections that would mean at least 96 SMA connectors
(that takes very large board space and implies some skew problems due to the
differences in the line lengths).

I once used the Tyco ZDOK system (plug + receptacle) for board-to-board
connections with up to 80 parallel signals but unfortunately  the
performance was not satisfactory, so I won't be using them again. Are there
any other interface systems for the above described purpose or ways to build
a highly-parallel highspeed  connection between two boards?

I appreciate every kind of suggestion and help. Thanks a lot in advance.

Regards, Maurice