[SI-LIST] Re: Routing differential lines as single ended traces ?
- From: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
- To: "Danny Damhave" <dd@xxxxxxxxxxx>, <si-list-bounce@xxxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>, <asparky@xxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Mon, 26 Sep 2011 15:44:00 -0700
Changing glass weaves has nothing to do with crosstalk. There have been
many papers done on skew induced in differential pairs due to glass weaves
that are not uniform in distribution of glass. Some have tired routing on
an angle, others have tried to route with the pitch of the glass.
The far simpler solution is to use glass weaves with uniform distribution.
Much has been written on this as well.
--------------------------------------------------
From: <asparky@xxxxxxxxxxxxxxxxxxxxxxxx>
Sent: Monday, September 26, 2011 2:47 PM
To: "Danny Damhave" <dd@xxxxxxxxxxx>; <si-list-bounce@xxxxxxxxxxxxx>;
<si-list@xxxxxxxxxxxxx>
Subject: [SI-LIST] Re: Routing differential lines as single ended traces ?
> 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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>>>
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