Re: comparing IBIS model simulation and measurements

Betty,

Is this slewrate measured into a simple test load, or into
a complex circuit on a PCB? A 6ns slewrate seems extremely
slow to me, unless there is a significant capacitive or trace
loading.

If this is truly the edgerate, then your original Spice model
for the buffer is significantly wrong.

regards,

scott

--
Scott McMorrow
Principal Engineer
SiQual, Signal Quality Engineering
18735 SW Boones Ferry Road
Tualatin, OR  97062-3090
(503) 885-1231
http://www.siqual.com
Betty Luk wrote:
> Hi,
>
> 1) simulated slewrate: 2ns (20-80%)
> 2) measured slewrate: 6ns
> 3) scope: Tektronix TDS680B, probe: Tektronix P6245
>
> Thanks,
> Betty
>
> > -----Original Message-----
> > From: Daniel Nilsson [mailto:Daniel.Nilsson@compaq.com]
> > Sent: Monday, November 27, 2000 4:57 PM
> > To: Betty Luk
> > Cc: 'ibis-users@eda.org'
> > Subject: Re: comparing IBIS model simulation and measurements
> >
> >
> > Hi,
> >
> > In order to help you with this I need more information:
> >
> > What is the slewrate you are simulating ?
> > What is the slewrate you are measuring ?
> > What measurement equipment are you using, scope model and
> > probe model ?
> >
> >
> > Regards
> > Daniel Nilsson
> >
> > Betty Luk wrote:
> > >
> > > Hi,
> > >
> > > I've created an IBIS model, and I'm using it with HyperLynx
> > BoardSim.
> > > These results correlate well with Spice simulations, which
> > leads me to
> > > believe that the IBIS model was created correctly from the Spice
> > > model.  On the net that I'm simulating, I'm using some Samsung IBIS
> > > models, and some passive components.
> > >
> > > Now I'm trying to compare the HyperLynx simulation with
> > measurements.
> > > I'm noticing that my simulation has a significantly faster slew rate
> > > than my measurements.  I've checked my scope probe, and they should
> > > have negligible effect on my measurements.  Is this most likely a
> > > deficiency with my original Spice model?
> > >
> > > I would appreciate any feedback!
> > >
> > > Thanks,
> > > Betty Luk
> > >
> >