Re: [SI-LIST] : Edge Rates

Bill Dempsey (bdempsey@dnaent.com)
Thu, 08 Jul 1999 17:54:04 -0500

I concur with the previous postings on edge rates (see below).

One little side note on all this. To "see" these edge rates you
need the proper equipment AND measurement techniques. Too often I
see and engineer with a 6-8" ground coupled half-way across the board
using a 500MHz scope with a junky probe stating that the output
doesn't have those kind of edge rates. Oh... and that the "noise" he
sees is .... yup... ground bounce.

So make sure you have the proper equip and techniques in use before
you go looking for these edge rates.

Regards,

Bill Dempsey
DNA Enterprises, Inc.

Scott McMorrow wrote:
>
> I concur with Tom. It is highly unusual to see
> a device these days that has an edge rate more
> than 500 ps. This means that almost every pc
> board trace must be considered a transmission line for
> analysis purpose. Most devices manufactured today
> also tend to have lower channel resistance than
> necessary (10 to 25 ohms), which will cause severe
> overshoot and ringback on unterminated nets.
>
> BTW, Tom also gives a great presentation with
> a breakdown of the measured edgerate characteristics
> of various devices.
>
> regards,
>
> scott
>
> tomda wrote:
>
> > Assume 100 to 500 psec for the full transition for any modern logic family
> > unless it has controlled edge rates.
> >
> > Tom Dagostino
> >
> > -----Original Message-----
> > From: Ken Patterson [SMTP:ken.patterson@pathway-inc.com]
> > Sent: Thursday, July 08, 1999 12:07 PM
> > To: si-list@silab.eng.sun.com
> > Subject: [SI-LIST] : Edge Rates
> >
> > I am a newcomer to signal integrity analysis and would like to know how
> > to find out what the typical edge rates (i.e. rise and fall times) of
> > some of the industry standard logic families are. These include FCT
> > logic, SDRAMs and Syncburst SRAMs . I have an upcoming project that
> > will use these devices and would loike to perform some signal integrity
> > analysis.
> >
> > Ken Patterson
> > Electronic Engineer
> > ADC Broadband Communications/Pathway Division
> > email:ken.patterson@pathway-inc.com
> >
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