FreeLists / si-list / [SI-LIST] Re: Choosing extraction frequency for package RLGC

["Zadehgol, Ata" <ata.zadehgol@xxxxxxxxx>]

Hi Frank,

That is a good question, personally the approach I'd like to take in
choosing the bandwidth for system simulations, model generation, and lab
data collection is to consider three main factors, these are as follows:
1.  The power spectral density of the transmitter device.
2.  The Transmit and Receive compliance requirements such as slew rate,
voltage level, etc..
3.  The protocol spec such as trise10%-90% vs. trise20%-80%, etc...
It is important to keep in mind the derivation of the 0.35/trise found
in Hspice manual or some other books as a quick approximation, which is
basically based on a 1st order approximation of passive system response
and 10%-90% assumptions; however, this may not necessarily apply exactly
to every design/optimization problem.  I personally prefer to take a few
moments up front and hand calculate the bandwidth requirements based on
the three items I outlined above, this will not only give the customized
bandwidth requirements for the specific design, but will also help
define the optimization goals more intuitively as well.  Hope this
helps.

Ata Zadehgol

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On
Behalf Of Frank Dunlap
Sent: Friday, January 02, 2004 1:08 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Choosing extraction frequency for package RLGC


I apologize if my question has been answered in previous postings.  I
searched the archives, yet did not find an answer.

From my understanding, an "extraction" frequency must be specified for
tools
that generate RLGC from package data.  My question is, "how does one
choose
an appropriate frequency?"

Note the excerpt below and take note of the implications of the last
sentence:

******************************************
Pages_5-21_5-22_from hspice_signal_integrity_guide.pdf

Some designers use 0.35/trise to estimate the skin effect frequency.
This
estimate is good for the bandwidth occupied by a transient, but not for
the
clock frequency, at which most of the energy is transferred. In fact, a
frequency of 0.35/trise is far too high and results in excessive loss
for
almost all applications. Simulation computes the skin effect frequency
from
1/(15*trise). If you use precomputed model parameters (ELEV =3D3D 2),
compute
the resistance matrix at the skin effect frequency.

******************************************

I've heard various opinions regarding frequency selection, yet wanted to
gather more opinions from you SI folks.

One other question: when working with a limited budget while dealing
with a
package that supports multiple interfaces that operate at different
frequencies, are there recommendations as to how to determine the best
frequency for RLGC extraction that yields reasonable results for all
interfaces?  Given only one frequency to use for the entire RLGC
extraction,
my choice would be to use an extraction frequency based upon the
requirements of the highest-frequency interface.

Thanks,

Frank

Some more search terms to aid others in finding this e-mail later:

RLC LCR RLGC=3D20
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