[SI-LIST] AW: Re: Routing differential lines as single ended traces ?
- From: "Havermann, Gert" <Gert.Havermann@xxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Mon, 26 Sep 2011 09:50:55 +0200
Hi Jerry,
on validation platforms or test fixtures it is beneficial to route single ended
instead of coupled. The reasons are, that the test equipment is single ended,
and that you don't want any PCB effects to mask the DUTs performance.
In Lab environments, you can live with the slightly worse noise performance (in
the lab you will hardly find any performance degradation unless you inject
noise).
I wouldn't use this scheme for anything else but testing as it needs too much
space on the PCB.
BR
Gert
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-----Ursprüngliche Nachricht-----
Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] Im
Auftrag von steve weir
Gesendet: Montag, 26. September 2011 04:23
An: si-list@xxxxxxxxxxxxx
Betreff: [SI-LIST] Re: Routing differential lines as single ended traces ?
On 9/25/2011 6:57 PM, Low Jerry wrote:
> Hi,
> I recently came across a validation platform where the LVDS
> differential lines are routed as single ended traces traces instead of
> tightly coupled differential pairs. The motivation I found was so that
> they could use each of the pairs as single ended traces when needed as
> well. When I probed deeper it seems like the person who proposed this
> scheme has left. So I would like to seek help here on some
> clarification
>
> - Will a scheme like this impact the performance of the
> differential pair
The scheme itself will not.
> ? Since I understand that differential routing is more immune to noise.
That is largely a myth. There are only a few very special circumstances where
tightly coupled pairs exhibit better noise rejection to PCB trace noise
aggressors than reasonably routed, loosely coupled pairs.
> - What are the considerations/feasiblity studies that need to be done
> before implementing a scheme like this ?
They are the same as with any signal integrity requirements. The scheme
doesn't impose anything extra. It does remove some headaches.
> - Since this is a validation platform what measures can be taken ensure
> that the performance seen are similar to a production platform if the
> production platform is routed in differential.
Homework gets done or it doesn't.
Steve
>
> Thanks in advance for the feedbacks. Have a great day.
>
>
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