[SI-LIST] Re: Power plane noise measurement
- From: "Vishram Pandit" <vishrampandit@xxxxxxxxxxx>
- To: Larry.Smith@xxxxxxx, si-list@xxxxxxxxxxxxx, adsurevv@xxxxxxxxx
- Date: Tue, 20 May 2003 19:54:12 +0000
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
Yahoo!? >>The New Yahoo! Search - Faster. Easier. Bingo.
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