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Standard backplanes with full ground plane?

For prototyping a large embedded system I am looking for a card rack with a good backplane. 20 or more slots, 64 or 96 pin DIN connector or similar, single height, maybe Eurocard-size. Preferably not Press-Fit but we can always hand solder, of course. Most of what's available is VME with super-wide power and ground traces but as far as I could make out from the data sheets no full ground plane. We've got analog stuff on most of the cards so a ground plane is important. The bottom (solder-side) layer should be traces so we can cut some for slot ID and analog stuff, can't use 100% internally bussed versions.

Short of laying out our own (again...), is there something with a ground plane that can be had off-the-shelf?

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Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg
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People actually still make backplanes without ground planes in them? You sure about that?

Try buying maybe one of the backplanes made for blade servers. Gotta be generic stuff out there.

You can't even do controlled impedence traces without planes.

del

Reply to
Del Cecchi

Blade servers, good point. I'll look if they have some that are 20-wide or more.

--
Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg

VME backplanes have ground planes, and we do all sorts of analog stuff in VME. Never had a problem we could blame on a backplane, even using a motley collection of ebay crates and a bazillion different customer situations.

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The slot ID thing would be a challenge with 3U VME. No problem in 6U.

John

Reply to
John Larkin

Yes, meantime I found some with planes. But all traces inside, can't unhook some of the DIN pins without major surgery. I guess we'll roll our own again then.

Nice! Interesting that you guys tend not to use the 2nd rail.

6U is too monstrous for this case. It's not just ID we need but also some near-realtime signaling from the boards to a host where the usual IRQ1 arbitration would take too long.

Question: Since you don't seem to use slot ID how do identical boards in one rack know which position they are in? DIP switches? Or maybe they don't have to know in your cases?

--
Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg

I wonder how many backplanes have been invented over the years. I've done a few myself.

The analog stuff is mostly slow, so we don't really need 32 bit transfers. Leaves more room on the board for stuff!

Doesn't CPCI have geographic addressing? Those backplanes are mass produced, too.

Dip switches. Nobody seems to mind.

John

Reply to
John Larkin

In ultrasound we ended up making our own. Every single time. Lack of slot ID was just one reason, there just weren't enough configurable lines, or in cases like VME there were none at all.

But they are overkill with their 220 pin connectors and you can usually only get them with 8 slots. Plus they are, gasp, metric ;-)

In this case that is bound to cause trouble because there will be dozens of boards that are going to be swapped a lot. DIP switches are also not reliable IMHO. When using the ADN8831 eval board for a TEC controller I was almost done tuning the PID when one broke off. Luckily someone had a sewing needle so I could move that position one more time.

--
Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg

The more i read, the more it seems, that what you want is VXI bus instead.

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 JosephKK
 Gegen dummheit kampfen die Gotter Selbst, vergebens.  
  --Schiller
Reply to
joseph2k

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