RE: about IO_Buffer model's ac analysis

> I think that ibs model was generated by spice's dc analysis and transient
> analysis,
> so ibs model don't contain frequency response information.
Frequency response information IS available in an IBIS model for its package
parasitics, and I think that's what matters here.

When I do an AC analysis, I am interested in the transfer function FROM some
point TO some other point in the circuit.

The first thing you need to think about, is where might the FROM and TO
nodes be when you have IBIS models?

It makes sense to look at transfer functions that might involve the device's
pad node, either FROM (driving out) or TO (as an input). The IBIS model
ought to have sufficient information about the device's package parasitics
(between the pad and the pin), for the simulator to be able to do an AC
analysis, within the accuracy limits of that package representation.

For a buffer driving out, you would replace the I/V curves with your AC
source. For a receiver, find the slopes of the I/V curves where they
intercept the DC operating point, and include that resistance, along with
c_comp, as the "load" on the end of the package.

It doesn't make sense to try to analyze THROUGH a buffer that is represented
by an IBIS model. The IBIS model of a buffer has no input, so there is no
such thing as a transfer function that includes that of the buffer itself.

> ----------
> From: Wenqing Zhang[SMTP:wqzhang@avanticorp.com]
> Reply To: wqzhang@avanticorp.com
> Sent: Tue, 27 March 2001, 08:12
> To: ibis-users@vhdl.org
> Subject: about IO_Buffer model's ac analysis
>
> hi, all,
>
> I has a problem.
> I think that ibs model was generated by spice's dc analysis and transient
> analysis,
> so ibs model don't contain frequency response information.
>
> now I want to realize ac analysis to ibs model version3.2 in Star-Hspice
> , but the simulation results
> were very bad.
> perhaps ibs model should contain frequency response information which were
> generated with spice's
> ac analysis.
>
> do you think my idea? pls help me.
>
> I am not a member of ibis-user, so pls email to:
> wqzhang@avanticorp.com
> --
> Thanks
> Wenqing Zhang
> ______________End Forwarded Message_________
> o:62834978-701
> Avant! Shanghai R&D Center, 16th Floor, SunTong InfoPort Plaza
> No.55, West Huaihai Road, Shanghai, 200030, P.R.China
>
>
 
Received on Tue Mar 27 09:17:11 2001