[SI-LIST] Re: UltraCAD ESR and Bypass Capacitor Caculator

  • From: Fred Balistreri <fred@xxxxxxxxxxxxx>
  • To: si-list@xxxxxxxxxxxxx
  • Date: Tue, 12 Aug 2003 09:16:37 -0700

In such an application where you have enough plane capacitance and
the location of the dicretes don't matter then why have them at all?
I presume that one is trying to lower/control the overall impedance of
the
power system. If so then the number of discretes and location may
matter.
What is your opionion Lee?

Best Regards,

Lee Ritchey wrote:
> 
> If capacitors make a difference at these frequencies, it means that you
> have inadequate plane capacitance.  You likely, also have excessive ripple
> which will manifest itself as occasional instabilities.  Specifically, when
> a large data bus switches from all 0 to all 1.
> 
> When you fix this with a good plane capacitor, the location of discretes
> won't matter.
> 
> Lee
> 
> Lee Ritchey
> leeritchey@xxxxxxxxxxxxx
> Why Wait?  Move to EarthLink.
> 
> > [Original Message]
> > From: Zhangkun <zhang_kun@xxxxxxxxxx>
> > To: <si-list@xxxxxxxxxxxxx>
> > Date: 8/4/2003 8:57:58 PM
> > Subject: [SI-LIST] Re: UltraCAD ESR and Bypass Capacitor Caculator
> >
> > Dear All:
> >
> > In our simulation and measurement, we found that power noise of at least
> 400MHz could be decoupled by discrete caps. The placement DOES matter the
> impedance of PDS. The current problem is the anti-resonance between
> different kinds of caps.
> >
> > Best Regards
> >
> > Zhangkun
> > 2003.08.05
> > ----- Original Message -----
> > From: "Juergen Flamm" <jflamm@xxxxxxxxxxx>
> > To: <si-list@xxxxxxxxxxxxx>
> > Sent: Tuesday, August 05, 2003 3:44 AM
> > Subject: [SI-LIST] Re: UltraCAD ESR and Bypass Capacitor Caculator
> >
> >
> > > A tool from Cadence called SPECCTRAQuest with the Power Integrity
> option =
> > > will not only allow you to evaluate various capacitor types and =
> > > quantities, but also include their placement locations, their
> individual =
> > > mounted inductances and a model of the plane pair they are connected
> to. =
> > > The plane model includes skin effect and dielectric losses. It is not =
> > > only pretty cool to use, but very accurate and shares the same database
> =
> > > with the Allegro layout tool.=20
> > >
> > > Check it out if you like. =20
> > >
> > > Regards=20
> > >
> > > Juergen Flamm
> > >
> > > -----Original Message-----
> > > From: Peterson, James F (FL51)
> [mailto:james.f.peterson@xxxxxxxxxxxxx]=20
> > > Sent: Monday, August 04, 2003 12:19 PM
> > > To: si-list@xxxxxxxxxxxxx
> > > Subject: [SI-LIST] Re: UltraCAD ESR and Bypass Capacitor Caculator
> > >
> > > Doug,
> > >
> > > In regards to :=20
> > >
> > > <snip>
> > > 1. The reason we wrote the calculator in the first place was because
> we=20
> > > couldn't figure out how to make the frequency response calculation for =
> > > an=20
> > > arbitrary number of capacitors with arbitrary values, inductance and
> ESR =
> > >
> > > any other way. Then we figured others might have the same problem and =
> > > would=20
> > > like access to the same tool.
> > > <snip>
> > >
> > > We've been having excellent results doing this very thing using PSPICE.
> > >
> > > We get complete control over ESR and ESL values, qty of caps, and their
> > > values.=20
> > >
> > > We plot the results as ohms and freq (log) - which requires a little
> > > config...
> > >
> > > regards,
> > > Jim Peterson
> > >
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: Doug Brooks [mailto:doug@xxxxxxxxxx]
> > > Sent: Monday, August 04, 2003 1:42 PM
> > > To: si-list@xxxxxxxxxxxxx
> > > Subject: [SI-LIST] Re: UltraCAD ESR and Bypass Capacitor Caculator
> > >
> > >
> > > As the author of this calculator, I guess I'd like to throw in my 2 =
> > > cents=20
> > > worth!
> > >
> > > 1. The reason we wrote the calculator in the first place was because
> we=20
> > > couldn't figure out how to make the frequency response calculation for =
> > > an=20
> > > arbitrary number of capacitors with arbitrary values, inductance and
> ESR =
> > >
> > > any other way. Then we figured others might have the same problem and =
> > > would=20
> > > like access to the same tool.
> > >
> > > 2. The calculator helps demonstrate (as does our article) that one
> thing =
> > >
> > > that is REALLY desired for a smooth impedance response is a continuum
> of =
> > >
> > > capacitor self resonant frequencies  (not necessarily simply
> capacitor=20
> > > VALUES). A large number of caps with the same self resonant frequency =
> > > gives=20
> > > you a single deep zero. Many self resonant frequencies spread over a =
> > > range=20
> > > give you multiple zeros, spreading out the response much more =
> > > effectively.=20
> > > MORE IMPORTANTLY, these zeros (and don't forget the poles in between) =
> > > REACT=20
> > > with each other to provide a smoother response. The calculator helps
> you =
> > >
> > > demonstrate and prove that.
> > >
> > > 3. Along the way, the results from the calculator provided the
> evidence=20
> > > (unexpected at the time) that moderate ESR is better than low ESR.
> The=20
> > > reason is that while low ESRs give you very deep zeros, they also lead =
> > > to=20
> > > very high peaks. Moderate ESR gives you an OVERALL better frequency
> > > response.
> > >
> > > 4. Finally, the calculator does not address the issue of placement.
> My=20
> > > input on that question is this: Placement doesn't much matter EXCEPT
> for =
> > >
> > > (a) the electrons must be able to get where they are needed in time=20
> > > (traveling at 6"/ns) and (b) loop areas (including those around and =
> > > through=20
> > > caps) must be minimized for EMI reasons. Most people are aware of
> these=20
> > > issues, and if they are taken care of, THEN placement is no longer an =
> > > issue.
> > >
> > > Hope this helps
> > >
> > > Doug Brooks
> > > >
> > >
> > > Doug Brooks' new book, "Signal Integrity Issues and Printed Circuit =
> > > Board=20
> > > Design" has just been released by Prentice Hall. See details and =
> > > ordering=20
> > > info at www.ultracad.com
> > >
> _________________________________________________________________________=
> > > ___
> > > __
> > >
> > >
> > > ------------------------------------------------------------------
> > > To unsubscribe from si-list:
> > > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
> > >
> > > or to administer your membership from a web page, go to:
> > > //www.freelists.org/webpage/si-list
> > >
> > > For help:
> > > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> > >
> > > List archives are viewable at:    =20
> > > //www.freelists.org/archives/si-list
> > > or at our remote archives:
> > > http://groups.yahoo.com/group/si-list/messages=20
> > > Old (prior to June 6, 2001) list archives are viewable at:
> > >   http://www.qsl.net/wb6tpu
> > >  =20
> > > ------------------------------------------------------------------
> > > To unsubscribe from si-list:
> > > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
> > >
> > > or to administer your membership from a web page, go to:
> > > //www.freelists.org/webpage/si-list
> > >
> > > For help:
> > > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> > >
> > > List archives are viewable at:    =20
> > > //www.freelists.org/archives/si-list
> > > or at our remote archives:
> > > http://groups.yahoo.com/group/si-list/messages=20
> > > Old (prior to June 6, 2001) list archives are viewable at:
> > >   http://www.qsl.net/wb6tpu
> > >  =20
> > >
> > > ------------------------------------------------------------------
> > > To unsubscribe from si-list:
> > > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
> > >
> > > or to administer your membership from a web page, go to:
> > > //www.freelists.org/webpage/si-list
> > >
> > > For help:
> > > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> > >
> > > List archives are viewable at:
> > > //www.freelists.org/archives/si-list
> > > or at our remote archives:
> > > http://groups.yahoo.com/group/si-list/messages
> > > Old (prior to June 6, 2001) list archives are viewable at:
> > >   http://www.qsl.net/wb6tpu
> > >
> > >
> > ------------------------------------------------------------------
> > To unsubscribe from si-list:
> > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
> >
> > or to administer your membership from a web page, go to:
> > //www.freelists.org/webpage/si-list
> >
> > For help:
> > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> >
> > List archives are viewable at:
> >               //www.freelists.org/archives/si-list
> > or at our remote archives:
> >               http://groups.yahoo.com/group/si-list/messages
> > Old (prior to June 6, 2001) list archives are viewable at:
> >               http://www.qsl.net/wb6tpu
> >
> 
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
> 
> or to administer your membership from a web page, go to:
> //www.freelists.org/webpage/si-list
> 
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> 
> List archives are viewable at:
>                 //www.freelists.org/archives/si-list
> or at our remote archives:
>                 http://groups.yahoo.com/group/si-list/messages
> Old (prior to June 6, 2001) list archives are viewable at:
>                 http://www.qsl.net/wb6tpu
> 

-- 
Fred Balistreri
fred@xxxxxxxxxxxxx

http://www.apsimtech.com
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List archives are viewable at:     
                //www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages 
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
  

Other related posts: