[SI-LIST] Re: Termination of unused Ethernet pairs
- From: "Lee " <leeritchey@xxxxxxxxxxxxx>
- To: <james.dowle@xxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Tue, 17 Jun 2014 14:56:43 -0700
No downside I know of.
-----Original Message-----
From: James Dowle
Sent: Tuesday, June 17, 2014 2:37 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Termination of unused Ethernet pairs
Hi
I've got an board with 10/100 Ethernet on it and we have no margin in
conducted emissions tests for the Ethernet port, If I disconnect the
termination on the unused pairs we get 3 dB margin. I don't like the idea
of removing the termination on the unused pairs but it is the only solution
giving us any margin on the conducted emissions test.
The individual pairs are sorted together as we've allow for a variant of
the design that uses PoE each pair is then terminated via a 47 ohm resister
and a 22nF cap, We've tried different resister and capacitor values with no
difference, the active and unused pairs termination are all then tied
together and then grounded to the chassis ground via a 1nF 2kV cap.
What's the downside of removing the termination on these pairs?
Thanks
James
James Dowle
Senior FPGA designer
MimoMax wireless Ltd
540 Wairakei rd
Christchurch
phone +64 3 3586697
james.dowle@xxxxxxxxxxx
http://www.mimomax.com/
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