I'm lacking the experience of LVDS over flat ribbon cable that should be twisted, but is not. Different pairs will couple with the next and with the outside depending on frequency and length, but by how much ? The motivation for the question comes from the rather limited number of possible crimping locations a twisted ribbon cable provides. Whereas a flat ribbon cable can be crimped at any arbitrary millimeter.
I'd be using it for short runs, below 0.5m alltogether
Rene
What's your data rate, and what parts will you be using?
That length will be fine for most things short of the ultra-speed stuff. It's recommend 3 or 4 wires per LVDS pair, with a ground between a pair and anything else
gnd a+ a- gnd b+ b- gnd ...
The really fast stuff might get nasty over a half meter of standard ribbon cable.
John
Thanks John, It'll be 20MHz to 60MHz or so. The parts will be
65LVDS1 @ 65LVDS2. They'll synchronize different subsystems in a distributed setup.Rene
Not super fast, so you should be OK. Be careful to keep the pair skew down by routing equal length traces in/out of the ribbon cable connectors. But it's not really hairy... 100 ps or so shouldn't break anything.
Anybody know the differential impedance for a regular Scotchflex type cable in this config, diff pairs with outside grounds? I'm too lazy to TDR it.
John
Could also use that fancy ribbon cable that is wrapped in a flat shield.
[snip]
But you should TDR it, so that you really know, rather than guess ;-)
...Jim Thompson
I didn't guess. But at the moment, I don't need to know.
John
What you don't mean won't hurt you.
Bob
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