[SI-LIST] Re: Routing differential lines as single ended traces ?
- From: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
- To: "Danny Damhave" <dd@xxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Mon, 26 Sep 2011 12:45:48 -0700
If you use the right glass weave it is not necessary to be concerned about
skew. No need for tricky routing.
--------------------------------------------------
From: "Danny Damhave" <dd@xxxxxxxxxxx>
Sent: Monday, September 26, 2011 12:24 PM
To: <si-list@xxxxxxxxxxxxx>
Subject: [SI-LIST] Re: Routing differential lines as single ended traces ?
> Hi,
> Routing a LVDS differential pair with a tightly coupling, is sensitive to
> production tolerances/variation eg. etching factor/coating.
> Having a weak coupling or using the not closer than rule (single ended
> traces) is less sensitive.
> If your traces are wide and your timing is very critical is probably best
> to route with a very weak or weak coupling and match the trace to trace
> spacing with the pitch of the glass fibres in your laminate to reduce the
> skew between the signals, but of course this can also be achieved by
> staying away from 90deg routing and using the not closer rule.
> I assume that your signals always have a reference plane, are not close to
> any edge of the PCB, do not leave the board , and are not close to noise
> sources like DC DC switchers and your signals are not influenced by PCB
> resonances or the like.
> BR
> Danny Damhave
>
>
>
> On 26/09/2011, at 03.57, 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
>> ? Since I understand that differential routing is more immune to noise.
>> - What are the considerations/feasiblity studies that need to be done
>> before implementing a scheme like this ?
>> - 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.
>>
>> Thanks in advance for the feedbacks. Have a great day.
>>
>>
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