[SI-LIST] Re: Power plane noise measurement
- From: "istvan novak" <istvan.novak@xxxxxxxxxxxxxxxx>
- To: <vishrampandit@xxxxxxxxxxx>, <Larry.Smith@xxxxxxx>,<si-list@xxxxxxxxxxxxx>, <adsurevv@xxxxxxxxx>
- Date: Tue, 20 May 2003 21:02:56 -0400
Vishram,
Converting S11 values into impedance does work as long as you
dont want to measure impedances below about 0.1 ohms. For
low impedance values you still can use a network analyzer, but
you have to connect both ports. You can search the archives of
the si-list for past threads on the topic. Also, there was a half-day
TecForum at DesignCon 2003 in Santa Clara earlier this year,
where five companies presented power-distribution measurement
techniques. Parts of it are available online, and an updated version
of the TecForum will be presented late June in Boston, at
DesignCon East 2003.
regards,
Istvan Novak
SUN Microsystems
----- Original Message -----
From: "Vishram Pandit" <vishrampandit@xxxxxxxxxxx>
To: <Larry.Smith@xxxxxxx>; <si-list@xxxxxxxxxxxxx>; <adsurevv@xxxxxxxxx>
Sent: Tuesday, May 20, 2003 3:54 PM
Subject: [SI-LIST] Re: Power plane noise measurement
>
>
> Can anyone of you please elaborate about the measurement techniques? If I
> want to measure
>
> 1] Time domain noise between power and ground,
>
> 2] Frequency domain Impedance between power and ground,
>
> what are the best ways of doing that?
>
> If I have a special SMA connector at the point of interest (between power
> andground), I can use a network analyzer, to measure S11. Will this be of
> anyuse? Also, if I want to measure the impedance at different points
> including the BGA pads, where it is very difficult to have special
> connector,what is the best approach?
>
> Thanks for your reply,
>
> Vishram PanditSenior Member Technical Staff SI/EMC Engineering Hughes
> NetworkSystems (301)428-5725
>
>
>
> >Virendra - To get a clean measurement of your power distribution >system,
> you will want to remove the decoupling capacitor from it's pads >before
> probing them. >>If the capacitor is left in place, it will "color" the
> measurement. The >decoupling capacitor mounted on the pads has a resonant
> frequency. The >inductance for this resonant circuit is in the vias and
> mounting pads >and in the height of the capacitor if you attach probes to
> thetop of >it. You will be measuring across the inductance which is highly
> >involved in the resonant circuit and will measure mostly noise at the
> >"selfresonant frequency". >>Usually, there are many small capacitors on a
> product. Pick one out of >a common value. For example, if there are 10 x
.01
> uF caps, remove one >out of the 10. It will not have a large effect on the
> PDS that you are >measuring. >>regards, >Larry Smith >Sun Microsystems
> >>>Delivered-To: si-list@xxxxxxxxxxxxx >>Date: Tue, 20 May 2003 10:28:36
> -0700 (PDT) >>From: Virendra >>Subject: [SI-LIST] Power plane noise
> measurement >>To: si-list@xxxxxxxxxxxxx >>MIME-Version: 1.0
> >>Content-Transfer-Encoding: 8bit >>X-archive-position: 6885
> >>X-ecartis-version: Ecartis v1.0.0 >>X-original-sender:
adsurevv@xxxxxxxxx
> >>X-list: si-list >>>>>>Hi all, >>>>i am trying to measure noise on a PCB
> directly across a decoupling capacitor. >The PCB has buried/ blind vias
and
> has no specific power noise test points. My >question is, will there be a
> difference in the measured noise if i measure noise >across the capacitor
> andif i remove the capacitor and probe at the pads? I >cannot remove the
> capacitor to do a what-if as i have only one board. >>>>thanks in advance,
> >>>>Virendra Adsure >>>>>>>>--------------------------------- >>Do you
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