Re: [SI-LIST] : crosstalk through resistor networks?

Mark McKee (mmckee@cisco.com)
Mon, 17 Aug 1998 15:39:24 -0700

fabrizio zanella wrote:

> Andrew, great timing on your question!
> I was just measuring crosstalk last week on a driver board plugged into a
> backplane with terminator boards on the back side. The terminator boards
> have CMD resistor packs (GTL+ pull up terminations), the input signal is
> GTL+, 1ns rise/fall time, 8 data lines switching, all terminated in same
> resistor pack. I measured the crosstalk attributable to the QSOP resistor
> packs to be ~ 2.5%, or 25mV peak to peak.
> Hope this helps,
> Regards,
> Fabrizio Zanella
> EMC
> fzanella@emc.com
> -------------
> Original Text
> From: "Andrew Phillips" <andrew@scs.ch>, on 8/14/98 9:07 AM:
> To: smtp@Eng@EMCHOP1["SI-LIST" <si-list@silab.Eng.Sun.COM>]
>
> Hello,
>
> I am interested in using some small-package (QSOP) resistor networks for
> terminating a large number of bus-signals in a design. Signal rise-times
> range from ~200ps to 1ns or so.
>
> I have found some devices that look suitable here:
> http://www.bourns.com/cat/MNETXX1.htm
>
> I am wondering whether such an approach will have crosstalk problems.
> Has anyone analysed this and can give me some advice?
>
> I presume that if traces are suitably separated before and after the
> resistor package then the crosstalk induced between adjacent signals
> will be reduced. These signals are very close together for the 3mm or so
> across the resistor package - is this likely to cause problems?
>
> Thanks for any help,
>
> Andrew Phillips
> Supercomputing Systems AG
> Zurich, Switzerland
>
> Need 'C6x DSP info?
> http://www.scs.ch/~andrew/c6x.html
> *
>
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Were the resistor packs the type with the common power pin or was it several discrete resister just packaged in the same QSOP. If it was the latter, was the via-redistribution stitches that connect the pads of the resistor
unique to the power plane (i.e. a one for one via to pad relationship verses a single via for multiple power pin pads. The measurements you are doing are something I've wanted to do for sometime. Thanks for sharing your data
points.

Mark

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