Re: [SI-LIST] : trace to trace coupling

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From: Muhammad S. Sagarwala (msagarwa@san-jose.tt.slb.com)
Date: Sat Sep 16 2000 - 17:29:15 PDT


Scott,

This explains it. I had the following configuration in mind

===================================== plane

                      =========
trace

===================================== plane

                      =========
trace

=====================================plane

and with this configuration I was really surprised to find 1V crosstalk in
the Z - axis.

Now, I totally agree with your viewpoint.

Thanks again,

Muhammad

-----Original Message-----
From: Scott McMorrow <scott@vasthorizons.com>
To: Muhammad S. Sagarwala <msagarwa@san-jose.tt.slb.com>
Cc: Sean Murray <seandm@mmspec.com>; si-list@silab.eng.sun.com
<si-list@silab.eng.sun.com>
Date: Friday, September 15, 2000 7:26 PM
Subject: Re: [SI-LIST] : trace to trace coupling

>Muhammad,
>
>I just did a "quick" simulation with the following trace configuration:
>
>============================= plane
>
> ===== signal
>
> ===== signal
>
>============================== plane
>
>Er = 4.2
>trace width is 5 mils
>trace to plane spacing is 5 mils
>trace to trace layer seperation is 5 mils
>
>z-axis parallelism is 2 inches
>
>
>The victim net contains a low currentXilinx Virtex 2ma driver on one end
and
>a receiver on the other end.
>
>The aggressor net contains a high current Xilinx Virtex PCI driver on
>one end and a receiver on the other end.
>
>For this particular configuration the simulated crosstalk at the
>receiver is about 700 mV.
>
>In the following configuration the crosstalk is 1000 mV:
>
>============================= plane
>
> ===== ==== Aggressors
>
> ===== Victim
>
>============================== plane
>
>
>It is not unusual to find these sorts of parallelism on boards that
>have been autorouted and not checked for parallel tracks on
>adjacent layers. It is especially hideous if the aggressors have
>strong drivers (like a PCI bus driver) and the victim is senstive
>to noise.
>
>
>regards,
>
>scott
>
>
>--
>Scott McMorrow
>Principal Engineer
>SiQual, Signal Quality Engineering
>18735 SW Boones Ferry Road
>Tualatin, OR 97062-3090
>(503) 885-1231
>http://www.siqual.com
>
>
>
>"Muhammad S. Sagarwala" wrote:
>
>> Hi Sean,
>>
>> Could you quote an example where you saw 1Volt xtalk due to z-axis
>> parallelism on striplines.
>> I mean what was the stackup-like and what was the frequency/magnitude of
the
>> signals.
>>
>> Curious,
>>
>> Muhammmad
>> -----Original Message-----
>> From: Scott McMorrow <scott@vasthorizons.com>
>> To: Sean Murray <seandm@mmspec.com>; si-list@silab.eng.sun.com
>> <si-list@silab.eng.sun.com>
>> Date: Friday, September 15, 2000 2:15 PM
>> Subject: Re: [SI-LIST] : trace to trace coupling
>>
>> >Sean,
>> >
>> >Almost every frequency and edge rate today. I would never ship out
>> >a board without performing a crosstalk analysis on every net, especially
>> >those that are on adjacent stripline layers. We often see more than
>> >1 Volt of crosstalk from z-axis parallelism.
>> >
>> >regards,
>> >
>> >scott
>> >
>> >--
>> >Scott McMorrow
>> >Principal Engineer
>> >SiQual, Signal Quality Engineering
>> >18735 SW Boones Ferry Road
>> >Tualatin, OR 97062-3090
>> >(503) 885-1231
>> >http://www.siqual.com
>> >
>> >
>> >Sean Murray wrote:
>> >
>> >> Does anyone know the formula in order to calculate the coupling
>> percentage
>> >> between two signals seperated by a solid ground plane? At what
>> >> frequency/edge rate does one have to start thinking about staggering
>> their
>> >> traces so that they do not get coupling between two stripline layers..
>> >>
>> >> Regards,
>> >> Sean Murray
>> >> General Manager
>> >>
>> >> M&M Specialties Inc.
>> >> 1236 W. Southern Ave. #106
>> >> Tempe, AZ. 85282-4518
>> >> Phone: (480) 858-0393 x105
>> >> Cell: (602) 684-7859
>> >> Fax: (480) 858-1882
>> >> Email: seandm@mmspec.com
>> >> WWW.mmspec.com
>> >>
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