[SI-LIST] Re: IBIS model doubt
- From: "Seshadri Venkataramanan" <jayanth.neo@xxxxxxxxx>
- To: "Canes Venatici" <starsilic@xxxxxxxxx>
- Date: Fri, 17 Oct 2008 02:24:30 -0700
HI Canes,
I have a question that I want to ask you.
Any IBIS Tool basically uses spice or some simulator in the backend to
process the required information for an IO buffer. If you don't connect a
specific load to the IO pin, how can you measure the data? what you say may
be possible for a driver that drives a transmission line, but cannot be said
in general?
And for example, if we have an I-V curve and a V-t curve for a specific
output pin, I think the IBIS Model is validated by comparing the V-t
waveform( rising or falling) for a specific load and the corresponding I-V
point for the same load.
I just wanted to present my view here of what is exactly happening while
developing an IBIS Model.
People here can correct me if am wrong. I am in the learning process.
On Thu, Oct 16, 2008 at 10:52 PM, Canes Venatici <starsilic@xxxxxxxxx>wrote:
> Hi all,
> I have some doubts regarding the usage of IBIS models.
> In the IBIS model,
> 1. Ramp measurement is done with a default value of 50ohms
> (R_load) connected to vref.
> 2. Also Rising/Falling waveforms can be simulated/measured with
> R_/L_/C_fixture/V_fixture.
> 3. Cref and Rref for specifying the way delay was measured by the
> manufacturer.
>
> With the above information incorporated in the IBIS file, if used for
> simulating
> will it be correctly representing the I/O?
> For e.g. with R_/L_/C_fixture/V_fixture/R_load effects included in the
> waveform data, if I make
> some external terminations, it is in addition to the R_fixture/R_load and
> may not correctly represent the system.
>
> Instead, why don't we have only the un-loaded I/O buffer modeled in the
> IBIS so that
> the designer who is using IBIS can put appropriate interface and do the
> simulations.
>
> Regards,
> Canes
>
>
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--
Seshadri Venkataramanan
Graduate Student
MS - Electrical Engineering
( Mixed Signal Circuit Design) / Student Design Intern.
Arizona State University/ NXP Semiconductors.
Lewis Mumford - "Our national flower is the concrete cloverleaf."
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