[SI-LIST] Connection to cable shields
- From: "Chris Chalmers" <cchalmers@xxxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Thu, 19 Aug 2004 16:54:20 +0100
Si list,
Where to ground a cable. I always get mixed up on where. This a
corner case which I am just not sure on and I wondered if someone
could just give me a nudge in the right
direction. The following case is
[ 10m shielded twisted pair [
source [ > -----------------------------------------> [ Load
[ [
[ [
chassis chassis
The signals traveling the cable are LVDS at ~400Mb/s.
They all transmit (no receivers at the source end).
The source's DGND is connected to the Chassis at the
point of exit of the cable. The cable screen is connected
to the chassis. I believe this is right.
At the load end, I don't know whether to ground DGND
to the chassis or not. Or even ground the cable shield
to the chassis. The load end circuitry DOES NOT have
its own GND. The returning current from the receivers at
the load end flows back down the cable to the source. The
chassis at the load end does not have a connection to GND.
For high speed signals I want to create a magnetic
shield so I think I need both ends of the cable shield connected
to the chassis's. I also think I need the source end DGND
connected to the source chassis. However, I am not convinced
I need the load end DGND connected to the load end chassis.
The circuitry at the load end works at 5V.
Any help with this would be most appreciated.
Thanks
Chris
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