[SI-LIST] Re: Routing differential lines as single ended traces ?
- From: asparky@xxxxxxxxxxxxxxxxxxxxxxxx
- To: "Danny Damhave" <dd@xxxxxxxxxxx>, si-list-bounce@xxxxxxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Mon, 26 Sep 2011 21:47:57 +0000
Why do you think changing glass weaves increases crosstalk?
Thanks,
Aubrey
Sent from my Verizon Wireless BlackBerry
-----Original Message-----
From: Danny Damhave <dd@xxxxxxxxxxx>
Sender: si-list-bounce@xxxxxxxxxxxxx
Date: Mon, 26 Sep 2011 21:59:31
To: <si-list@xxxxxxxxxxxxx>
Subject: [SI-LIST] Re: Routing differential lines as single ended traces ?
Right, but then we get more crosstalk instead ;-)
BR Danny Damhave
On 26/09/2011, at 21.45, Lee Ritchey wrote:
> 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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