Re: [SI-LIST] : Terminator location with larger BGA's

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From: Scott McMorrow (scott@vasthorizons.com)
Date: Fri Apr 07 2000 - 16:24:20 PDT


Chris,

Are you asking this question because you can't believe that a
170ps edge can propagate through the package, or that the
drivers in an FPGA can switch that fast?

regards,

scott

Chris Cheng wrote:

> i would love to know what kind of fpga can generate a 170ps edge coming
> out of the package.
> chris
>
> -----Original Message-----
> From: mcgiffb@ttc.com [mailto:mcgiffb@ttc.com]
> Sent: Friday, April 07, 2000 1:17 PM
> To: si-list@silab.eng.sun.com
> Subject: [SI-LIST] : Terminator location with larger BGA's
>
> We are using some 484 pin BGA's (FPGA's), which have edge rates of about
> 170ps.
> Using a series termination, it would have to be placed within 1/10 of the
> transition length according to Howard Johnson. On FR4, the transition length
> would be .98, making the distance from source to termination .098. It is not
> possible to get all of the required termination's within that distance.
>
> Aside from slowing down the edges (not desirable), waiting longer for things
> to
> settle, or going with buried resistance, are there any other solutions for
> placement of termination's? How are other people terminating large, high pin
> count devices?
>
> Thanks
>
> Bill McGiffin
>
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--
Scott McMorrow
Principal Engineer
SiQual, Signal Quality Engineering
18735 SW Boones Ferry Road
Tualatin, OR  97062-3090
(503) 885-1231
http://www.siqual.com

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