Re: [SI-LIST] : effect of trace width on the performance

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From: Muhammad S. Sagarwala (msagarwa@san-jose.tt.slb.com)
Date: Tue Oct 31 2000 - 18:33:01 PST


I am sorry...I should be a bit more specific....

Well the board with 7.5 mil wide traces has a lot of ground bounce.....

Hope this would help narrow down the possiblities...

Muhammad

-----Original Message-----
From: Bill Owsley <owsley@cisco.com>
To: Muhammad S. Sagarwala <msagarwa@san-jose.tt.slb.com>;
si-list@silab.eng.sun.com <si-list@silab.eng.sun.com>
Date: Tuesday, October 31, 2000 6:23 PM
Subject: Re: [SI-LIST] : effect of trace width on the performance

>not enough info, to reduce the wide range of possibles. One wild guess
>might be not enough copper...
>such as; what is the bad behaviour? Jus spank'm and send them to the
>corner...
>
>
>At 05:34 PM 10/31/2000 -0800, Muhammad S. Sagarwala wrote:
>>Hi SI Gurus,
>>
>>I am in a big problem. I designed two boards which are pretty much the
same.
>>The changes between them are:
>>
>>(1) One has traces that are 7.5 mils wide and the other has 9 mils wide
>>traces (both have a characteristic impedence of 50 ohms)
>>(2) The one that has 9 mil wide traces has 1 oz copper for the pwr planes
>>and the one with 7.5 mil wide traces has 0.5 oz. copper
>> on pwr planes.
>>
>>The stackup is pretty much the same.
>>The Frequency of signals on the boards is 400 Mhz.
>>The decoupling scheme on both boards is pretty much the same.
>>
>>
>>The problems is the board with 9 mil wide traces and 1oz. copper is
>>performing very good and the other board with 7.5 mil wide
>>traces and 0.5 oz. copper is behaving very very bad.
>>
>>My question is "do you think these changes make a big difference or is
>>there another variable(s) that I am missing?????"
>>
>>Comments suggestions are most welcome....(I need to be sure before I make
>>a decision to respin the board )
>>
>>Muhammad
>>
>>
>>
>>
>>
>>
>>
>>
>>Muhammad S. Sagarwala
>>Schlumberger SABER
>>Ph. (408) 586 7065
>>Fax (408) 586 4668
>
>----------------------------
>Bill Owsley, owsley@cisco.com
>919) 392-8341
>
>TMBU Compliance
>Cisco Systems
>7025 Kit Creek Road
>POB 14987
>RTP. NC. 27709
>
>
>

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