Re: [SI-LIST] : trace width for clock routing- wider/narrower?

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From: S. Weir (weirsp@a.crl.com)
Date: Sun Mar 12 2000 - 17:29:08 PST


John,

Assuming stripline or microstrip construction, set the trace width to get
the required impedance and set the spacing to get the required crosstalk
isolation. The amount of attenuation for a given amount of spacing
required depends largely on the height to the nearest reflection plane, and
the parallelism to other traces. If 5/10 gives you 50 ohms, then 5/25 will
give roughly 6X the attenuation for any amount of parallelism beyond the
critical length that 5/10 gives you and still maintain 50 ohms.

The above does not hold true if you are using coplanar waveguide. There
were various discussions of CPW characteristics on this thread about a
month ago.

Regards,

Steve.
At 09:04 AM 3/13/2000 +0800, you wrote:

>Dear All SI experts,
>
>For clock routing, does wider trace width have more advantage than
>narrower one ,in term of better electrical properties, under the condition
>of same trace to space ratio and good match in impedance with source
>terminators?
>
>For example, 5 mils trace width with 10 mils trace spacing versus 10mils
>trace width with 20 mils trace spacing.
>
>Thank you for your helps in advance.
>
>John Lin
>SI Engineer
>Quanta Computer Inc.,Taiwan, R.O.C.
>Email: John@quantatw.com
>Tel: 886+3+3979000 ext. 5183

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