[SI-LIST] Re: RE：How can we get the resonance frequency and Q betwee
- From: Istvan Novak <istvan.novak@xxxxxxxxxxx>
- To: liewluping@xxxxxxxxx
- Date: Fri, 07 Dec 2012 08:34:39 -0500
LIU,
Regarding the 'gap', yes, if you have series resonances further away
with non-matched ESR values, the antiresonance peak gets bigger.
You can this gap on either side of a capacitor's series resonance. At
high frequencies, the die-package resonance is usually one order of
magnitude, sometimes up to two order of magnitudes higher than
the series resonance of the bypass capacitors and therefore the
penalty saturates and will not depend on the gap. On the lower-
frequency side having a larger capacitance value actually helps to
shrink this kind of gap.
Regards,
Istvan Novak
Oracle
On 12/6/2012 9:28 AM, Luping LIU wrote:
> Hi Istvan:
> Thank you for your message, both the 0.1uF and 1uF capacitors are 0402
> package, most of time we are using 1uF instead of 0.1uF or 10nF, some chip
> perfomance better,others make no differece. I was thinking that the 1uF
> caps will got a larger peak of anti-resonance with the same package (same
> pcb too )cause the capacitance "gap" is larger,am I right?
> My questions are based on your excellent work before, include the PDN
> impedance mesurement solutions, thin core and the controled ESR capacitors,
> Thanks again.
>
> LIU Luping
>
>
> Msg: #4 in digest
> Date: Wed, 05 Dec 2012 09:28:41 -0500
> From: Istvan Novak
> <istvan.novak@xxxxxxxxxxx<http://cn.mc153.mail.yahoo.com/mc/compose?to=istvan.novak@xxxxxxxxxxx>
> Subject: [SI-LIST] Re: RE：How can we get the resonance frequency and Q
> betwee
>
> LIU,
>
> Unless you use the 0.1uF capacitor in a smaller package, it likely will
> have the same or
> even higher inductance than the 1uF part, so at high frequencies lower
> capacitance
> does not help. You will get a higher-frequency self resonance from the
> 0.1uf part,
> but it is a narrow-band phenomenon, and therefore you will likely get an
> antiresonance.
> For core rails the instantaneous transient noise matters, and it can be
> minimized
> by avoiding peaks and dips in the impedance profile. This is where
> capacitors with
> the proper ESR can help.
>
> Regards,
>
> Istvan Novak
> Oracle
>
>
>
>
>
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