Re: [SI-LIST] : Stub Capacitance calculation

From: Scott McMorrow ([email protected])
Date: Mon Jul 31 2000 - 01:32:41 PDT

Ron,

I agree. In fact, some packages contain stubs from pin to die which can be
1/4 wavelength.

scott

```--
Scott McMorrow
Principal Engineer
SiQual, Signal Quality Engineering
Tualatin, OR  97062-3090
(503) 885-1231
http://www.siqual.com
Ron Miller wrote:
> There is a problem with this simplistic approach, and that is that the quarter wave effect
> becomes more important than the capacitance as frequencies get into the Gigahertz
> range.  If you must use SPICE then capacitance probably is the best you can do, but
> regardless of the capacitance, as the stub approaches 1/4 wavelength, it approaches a
> short in the frequency domain.  This is real, not just theory.
>
> Ron Miller
>
> > -----Original Message-----
> > From: Mendelsohn, Joseph P (Joseph)
> > Sent: Tuesday, July 25, 2000 12:02 PM
> > To:   'Prasanna S'; '[email protected]'
> > Subject:      RE: [SI-LIST] : Stub Capacitance calculation
> >
> > Check the url below for an Online calculator.  It reports Co/unit length
> >
> > http://www.emclab.umr.edu/pcbtlc/microstrip.html
> >
> >
> > -----Original Message-----
> > From: Prasanna S [mailto:[email protected]]
> > Sent: Tuesday, July 25, 2000 1:23 PM
> > To: '[email protected]'
> > Subject: [SI-LIST] : Stub Capacitance calculation
> > Importance: High
> >
> >
> > Hi All,
> >      How can I  calculate the Capacitance of a Microstrip trace Stub
> > with the trace routed in the component or top layer with a di-electric
> > thickness of 3 mils under the trace.The di-electric constant is Er=4.0.
> > and copper is 0.5 oz Can you give me the formula used for that? I am
> > looking for the answer in pF/inch.
> >
> > Regards,
> > Prasanna
> >
> >
> >
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```

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