I hope this helps the discussion. This is a very important topic for
those of us who are trying to make circuits that both work and comply
to EMI standards at the same time.
regards,
Larry Smith
Sun Microsystems
> From: "Grasso, Charles (Chaz)" <[email protected]>
> To: "'[email protected]'" <[email protected]>
> Subject: RE: [SI-LIST] : Noise Voltage levels vs. EMI levels
> Date: Tue, 27 Jul 1999 07:24:35 -0600
> MIME-Version: 1.0
>
> The most ubiquitous phrase used for noise - EMI levels translation
> is ground bounce. A term the experienced SI folks are very familiar with
> I'm sure. Indeed the EMC folk spend a lot of energy minimizing
> the noise that is developed across the ground plane inductance.
>
> A general rule of thumb is that "noise" on the ground plane should
> not exceed 300mV. (From Henry Ott - Noise Reduction
> Techniques in Electronic Circuits.)
> Thank you
> Charles Grasso
> StorageTek
> 2270 Sth 88th Street
> Louisville CO 80027
> Tel: (303)673-2908
> Fax(303)661-7115
>
>
> > ----------
> > From: Spencer, David H[SMTP:[email protected]]
> > Sent: Monday, July 26, 1999 10:03 AM
> > To: '[email protected]'
> > Subject: [SI-LIST] : Noise Voltage levels vs. EMI levels
> >
> > I'm looking to correlate PCB ground noise voltage to an EMI levels.
> >
> > My understanding goes as far as: the voltage is measured from the PCB
> > ground
> > input to a point on the board differentially. That voltage drop is the
> > noise voltage. The voltage drop tells us that there is common mode
> > current. If we knew the impedance between the two points we could then
> > calculate the common mode current.
> > Since every PCB and has different geometry's and cables (power and I/O),
> > the
> > difficult unknown is the impedance.
> >
> > My questions:
> > Is there is an absolute noise voltage level that should never be exceeded?
> > Is there a way to "accurately" quantify the impedance's of the PCB ground
> > plane and cables?
> > Can noise voltage become a PCB design specification?
> > Most importantly, when all is said and done, is there an "accurate"
> > correlation between noise voltage and EMI levels?
> >
> > Thanks for the input
> >
> > David Spencer
> > Xerox Corporation
> >
> >
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