Re: [SI-LIST] : USB Slope matching and RFI/EMI

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From: Yehuda D. Yizraeli (yehuda@zoran.co.il)
Date: Tue Oct 26 1999 - 08:50:49 PDT


Hello D. C.,

        Thanks for the quick answer. I looked at the spec and could not find
out whats the enlarge skew will cause to. Any idea OR any pointer to it..?

                                thanks in advance, yehuda

>
> "Yehuda D. Yizraeli" wrote:
> >
> > Hi,
> >
> > Just wondered if someone knows the nature of the requirement for
> > matching of the rise and fall slope time in the USB spec.
>
> Shalom Yehuda!
>
> The rise and fall times, as well as the crossover point, need to match
> for two reasons:
>
> 1) Receiver performance. Mismatch would take the receiver out of its
> best common-mode range and cause increased jitter. Thanks to SE0
> conditions USB can't require large receiver common-mode ranges.
> 2) EMI. Mismatches between the rise and fall, esp. in unshielded
> cables, result in large common-mode energies that radiate like crazy.
>
> --
> D. C. Sessions
> dc.sessions@vlsi.com
>
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>
>

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-------------------------------------------------------------------
   Yehuda D. Yizraeli

Zoran Microelectronics Ltd. E-mail : yehuda@zoran.co.il Advanced Technology Center Direct Tel: 972-4-85-45-795 P.O.B. 2495, Haifa 31204, Israel Operator : 972-4-85-45-777 http://www.zoran.com Fax : 972-4-8-551-550 -------------------------------------------------------------------

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