[SI-LIST] Re: Stack up for EMI reduction, plane resonance and u-strip radiation etc etc

  • From: "Istvan NOVAK" <istvan.novak@xxxxxxxxxxxxxxxx>
  • To: <Chris.Cheng@xxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
  • Date: Sun, 8 Feb 2004 18:06:30 -0500

Chris,

I am not speaking for Zhangkun, but in many of the real boards I have looked
at by measurements and simulation, you can see the evidence of antiresonance
between the plane capacitance and inductances of capacitors.  Chips (at
least on those boards I have looked at) did SHIFT the resonance frequency
slightly, but did not make the peak go away.  You are correct in saying that
if you sprinkle the board with capacitors, the resonance peak is suppressed.
But as you said in one of your recent postings, the devil is in the details:
sometimes you may need so MANY capacitors over the board area to
sufficiently suppress the resonance that it becomes a pain.

Regards,

Istvan Novak
SUN Microsystems

----- Original Message -----
From: "Chris Cheng" <Chris.Cheng@xxxxxxxxxxxx>
To: <si-list@xxxxxxxxxxxxx>
Sent: Monday, February 02, 2004 10:15 PM
Subject: [SI-LIST] Stack up for EMI reduction, plane resonance and u-strip
radiation etc etc


> Finally......
>
> Zhangkun,
>
> I am also curious about these 200-400MHz plane resonace. If you sprinkle a
> PCB with a wide range of caps with different values and at different
> location and with high power loading (ie real IC chips) at different
> location, do you still see pronounced peaks at 200-400MHz ? I have no
doubt
> a bare power/gnd plane pair can resonate at those frequencies, but I've
> never seen that case once realistic caps and loading (IC chips) is placed
on
> the PCB. Are these simulation results or measurements based on a real
system
> with chips and caps ?
>



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