[SI-LIST] Re: IBIS package R,L,C values
- From: V S <for_si2003@xxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Fri, 17 Sep 2004 08:17:23 -0700 (PDT)
Mani,
Every chip has two parts the package and silicon. The
silicon occupies a small area, let us say, 200 mils x
200 mils. While the complete package may be 1 inch x 1
inch. There is an interconnect between the silicon and
the package. This package is modeled using package
R,L,C values. The package interconnect can also be
modeled as a distributed element using ebd files. The
silicon itself have parasitics, mostly capacitive
load. Both the Pin R,L,C and the package R,L,C values
are should be taken into account (Most simulators do
it) when simulating.
In your case the package will not be taken into
account in case 2. You should see a box outlining the
driver receive when modeling as "ibis device".
The difference in the two case is usually small -
especially if the mismatch between the package
impedance and the board impedance is not significant.
But it will also depend upon the rise time. The
package impedance must be taken into account if you
are working on simulation correlation. Usually the
measurement are done on the motherboard that is
subtantially far from the actual die ( may be as much
as 1"). In such scenario, the signal at the die is
substantially different from the signal at the die
receiver. In such cases, it may be necessary to take
into account teh package R, L, C values.
Some Comments on Harjeet's replies
The PIN R, L, C values have priority over the
package R,L,C values.
- I do not think there is anything like Pin PIN R, L,
C values having priority over the package R,L,C
values. Both are taken into account.
PS: These R, L, C value are lumped values. For fast
edge rate these may not provide accurate results.
- It it true that these values are lumped valued. But
they are accurate in most cases. The vendors may
provide the ebd files that have distributed R,L,C
values rather than the lumped values. I beleive that,
if a vendor thinks that lumped R,L,C values are
"sufficiently accurate" for the frequency of concern ,
it is ok.
VS
--- Harjeet Randhawa
<harjeet.randhawa@xxxxxxxxxxxxxxxxx> wrote:
> The IBIS model file should have these parameters
> embedded in it.
> Specctraquest's Model GUI picks this information
> from the DML file
> itself.
>
> The PIN R, L, C values have priority over the
> package R,L,C values.
> If PIN R,L,C are not specified then I guess the
> Speectraquest simulator
> will take the Package R,L,C values into account.
>
> You can override the Package as well as Pin R, L, C
> values with your
> defined values.
> But again these should be in line with the package
> used.
>
> PS: These R, L, C value are lumped values. For fast
> edge rate these may
> not provide accurate results.=20
>
> Best Regards,
>
/---------------------------------------------------------/
> Harjeet S Randhawa,
> Nevis Networks India Pvt. Ltd,
> B-101, Bhau Patil Marg,
> 34, Aundh Road, Pune - 411 020.
> Tel: +91-20-403-3900, Xtn:290,
> Fax:+91-20-403-3904,
> Cell: 0-9890130611.
>
/--------------------------------------------------------/
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of sivagurunathan.mani@xxxxxxxxx
> Sent: Friday, September 17, 2004 1:37 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] IBIS package R,L,C values
>
> Hi,
>
> In IBIS model there is package properties where
> package R,L,C values are
> defined. Again in pin declaration for each pin RLC
> values are specified.
> What is the difference ,In specctraquest If we are
> assigning model as
> IBIS devices, And if we apply pin by pin with
> specified pin model as
> like IBIS I/O , IBIS Input etc. Will there be any
> difference in
> simulation results? Will package properties taken in
> to account ,if do
> as per case 2?
>
> Please help in this regard.
>
> Sivagurunathan.M
>
>
>
>
>
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Other related posts:
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