RE: about IO_Buffer model's ac analysis

Why am I receiving this email.... what is it pertaining to?

Keith E. Raymond
Project Manager - Real Estate & Facilities Management
930 Commonwealth Avenue
Boston, MA 02215-1212
617/278-4043
617/593-6396 (Cellular)

> -----Original Message-----
> From: Ingraham, Andrew [SMTP:Andrew.Ingraham@compaq.com]
> Sent: Tuesday, March 27, 2001 12:14 PM
> To: 'wqzhang@avanticorp.com'
> Cc: ibis-users@vhdl.org
> Subject: 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 09:53:14 2001