Re: [SI-LIST] : A Question About Power Noise.

Ron Miller (rmiller@Brocade.COM)
Thu, 18 Mar 1999 09:55:27 -0800

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A very good source of the s-parameters or impedances of chip caps is American
Technical Ceramics(ATC). Try their website or get their catalog which has impedance
curves vs frequency.

Ron Miller

Pat Zabinski wrote:

> Quite a few years ago, I performed a small study on capacitors
> used for decoupling, and the results showed:
>
> * given the same package style/size, use as large as
> capacitance as available (i.e., decreases impedance)
>
> * use the smallest package size that you can (i.e.,
> extends usable frequency range)
>
> Pat
>
> On Mar 17, 9:39am, Vinu Arumugham wrote:
> > Subject: Re: [SI-LIST] : A Question About Power Noise.
> > Mark,
> >
> > Is a low value of capacitance really important? At 1GHz+, the package
> inductance dominates the characteristics and so the impedance of a 0.1uF and a
> 100pF capacitor in an 0603 package will not be very different. As you point
> out,
> > for better performance at higher frequencies one would need a lower
> inductance 0402.
> >
> > Thanks,
> > Vinu
> >
> > Mark Randol wrote:
> >
> > > SMT 0603 ceramic caps are still pretty good at 1GHz+ as long as you keep
> > > the value under a couple 100pF. 0402's go up through a couple GHz.
> > >
> > > --
> > > ---------------------------------------------------------------
> > > Mark Randol, RF Systems Engineer | Motorola SPS, Inc.
> > > (602)413-8052 Voice | M/S EL379
> > > (602)413-4150 FAX | 2100 E. Elliot Road
> > > ryvw50@email.sps.mot.com | Tempe, AZ 85284
> > > ---------------------------------------------------------------
> > >
> > > **** To unsubscribe from si-list: send e-mail to
> majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list,
> for more help, put HELP. si-list archives are accessible at
> http://www.qsl.net/wb6tpu/si-list ****
> >
> >
> >
> >
> > **** To unsubscribe from si-list: send e-mail to majordomo@silab.eng.sun.com.
> In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP.
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> >
> >-- End of excerpt from Vinu Arumugham
>
> **** To unsubscribe from si-list: send e-mail to majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP. si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list ****

--
Ronald B. Miller  _\\|//_  Signal Integrity Engineer
(408)487-8017    (' 0-0 ') fax(408)487-8017
     ==========0000-(_)0000===========
Brocade Communications Systems, 1901 Guadalupe Parkway, San Jose, CA  95131
rmiller@brocade.com,  rbmiller@sjm.infi.net

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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> A very good source of the s-parameters or impedances of chip caps is American
Technical Ceramics(ATC).  Try their website or get their catalog which has impedance
curves vs frequency.

Ron Miller

Pat Zabinski wrote:

Quite a few years ago, I performed a small study on capacitors
used for decoupling, and the results showed:

        * given the same package style/size, use as large as
          capacitance as available (i.e., decreases impedance)

        * use the smallest package size that you can (i.e.,
          extends usable frequency range)

Pat

On Mar 17,  9:39am, Vinu Arumugham wrote:
> Subject: Re: [SI-LIST] : A Question About Power Noise.
> Mark,
>
> Is a low value of capacitance really important? At 1GHz+, the package
inductance dominates the characteristics and so the impedance of a 0.1uF and a
100pF capacitor in an 0603 package will not be very different. As you point
out,
> for better performance at higher frequencies one would need a lower
inductance 0402.
>
> Thanks,
> Vinu
>
> Mark Randol wrote:
>
> > SMT 0603 ceramic caps are still pretty good at 1GHz+ as long as you keep
> > the value under a couple 100pF.  0402's go up through a couple GHz.
> >
> > --
> > ---------------------------------------------------------------
> > Mark Randol, RF Systems Engineer        | Motorola SPS, Inc.
> > (602)413-8052 Voice                     | M/S EL379
> > (602)413-4150 FAX                       | 2100 E. Elliot Road
> > ryvw50@email.sps.mot.com                | Tempe, AZ 85284
> > ---------------------------------------------------------------
> >
> > **** To unsubscribe from si-list: send e-mail to
majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list,
for more help, put HELP.  si-list archives are accessible at
http://www.qsl.net/wb6tpu/si-list ****
>
>
>
>
> **** To unsubscribe from si-list: send e-mail to majordomo@silab.eng.sun.com.
In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP.
 si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list ****
>
>-- End of excerpt from Vinu Arumugham

**** To unsubscribe from si-list: send e-mail to majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP.  si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list ****

-- 
Ronald B. Miller  _\\|//_  Signal Integrity Engineer
(408)487-8017    (' 0-0 ') fax(408)487-8017                 
     ==========0000-(_)0000=========== 
Brocade Communications Systems, 1901 Guadalupe Parkway, San Jose, CA  95131
rmiller@brocade.com,  rbmiller@sjm.infi.net
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