[SI-LIST] [Fwd: Re: Stack up for EMI reduction,plane resonance and u-s trip radiation etc etc]
- From: Raymond Anderson <Raymond.Anderson@xxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Tue, 10 Feb 2004 13:50:14 -0800
Chris Cheng wrote:
>Istvan,
>You got me on this one, I really need to figure out where can the 200-400MHz
>noise on PCB comes from ?
>Is it :
>a) Core noise, IC internal switch noise which propagate through the package
>power pins to the PCB
>Ans : Beaten to death, package is the choke point. EMI noise radiates from
> ___________________________
>package not PCB
The low-pass characteristics of the package are not "brick-wall" in nature
but have a finite amount of attenuation. You can't really say that the
package attenuates all the noise emanating inside to insignificant levels.
The noise is attenuated, but some is still there and can excite resonant
structures.
-Ray Anderson
Sun Microsystems Inc.
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