[SI-LIST] Re: How to measure voltage drop on plane
- From: "Russell D. Moser" <r.moser@xxxxxxxxxxxxxxxxx>
- To: <zhang_kun@xxxxxxxxxx>, <reanderson@xxxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Mon, 19 Jul 2004 19:42:33 -0400
Professor Dr. Swaminathan [?] at the esteemed Georgia Tech Signal Integrity
lab led some excellent research and resultant papers on this subject. I had
the good fortune to fund some research with him several years ago. I hope
that he is still active. He and GT would be a great resource.
Regards,
___________________
Russell D. Moser
Orion Group
r.moser@xxxxxxxxxxxxxxxxx
www.theoriongroup.net
717.914.0116
717.503.6682 (cell)
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> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of zhangkun 29902
> Sent: Monday, July 19, 2004 7:23 PM
> To: reanderson@xxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: How to measure voltage drop on plane
>
> Dear Ray
>
> In Paul's paper "Modeling Electromagnetic Interference
> Properties of Printed Circuit Boards", he proposed how to
> measure the voltage drop on the ground net. I think this
> method is not suitable for the complex PCB.
>
> At one time, we are check one PCB with Intel. The engineer
> said that "the noise on the ground" was too large. I ask them
> how to measure "the noise on the ground". There is no answer.
>
> Is the voltage drop on the ground plane useful?
>
> Best Regards
>
> Zhangkun
> 2004.7.20
>
> ----- Original Message -----
> From: Ray Anderson <reanderson@xxxxxxxxxxxxx>
> Date: Monday, July 19, 2004 11:54 pm
> Subject: [SI-LIST] Re: How to measure voltage drop on plane
>
> > Zhangkun-
> >
> > The measurement of power/ground noise is a differential measurement
> > (even if you use a single-ended probe) of the power voltage
> (Vdd) with
> > respect to the associated ground voltage (Gnd).
> >
> > When making these sort of measurements you need to measure Vdd with
> > respect Gnd at the same XY spatial location for the measurement to
> > make sense. (i.e. vertically coincident). If you measure Vdd with
> > respect to Gnd where the Gnd node is physically offset some
> > significant distance (wrt lambda) then the measurement just doesn't
> > make sense.
> >
> > If the Gnd measurement point is offset from the Vdd
> measurement point
> > by only a small fraction of an inch instead exactly coincident with
> > the measured Vdd location that is probably an acceptably
> small error,
> > however if the offset is on the order of inches or more then the
> > measured voltage doesn't make sense. Why? Because you are measuring
> > voltages 'across time' where the time is the time-of-flight
> from the
> > Gnd node coincident with the Vdd node (which you should be
> using as a
> > reference) to the Gnd node which is distant (which you
> should NOT be
> > using as a reference). Measurements of voltage across time are
> > undefined, at least with respect to the measurement of power/ground
> > noise which you propose.
> >
> > -Ray Anderson
> >
> >
> >
> > Zhangkun wrote:
> >
> > >Dear all
> > >The power ground noise at one location is easy to measure. How to
> > measure voltage drop on plane at different location? Is it
> impossible?
> > There is one method proposed by C. R. Paul. However, the
> structure of
> > Paul's is too simple.
> > >
> > >Best Regards
> > >
> > >Zhangkun
> > >2004.7.19
> > >
> > >
> > >
> > .
> >
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