Alex,
o In Quad, check the tlp and cpl files to make sure they are a
physical realization.
o Use a 5Gs+ scope & a > 1GHZ probe with < 1pf
o Charcterize the load.
o Find out if the clock has more than one VI curve.
o Find out how nonlinear the clock driver is.
o Try comparing to spice.
Richard Mellitz, NCR
On Feb 28, 11:03am, "Hilbers, Alex" wrote:
> Subject: Ibis simulation versus Measurement
>
> Hello,
>
> lately I have been using an Ibis model of a clock. As I use a Quad
> simulator, the Ibis model is converted to a Quad model. Although a V-T
> table is included to describe the waveform, there is a distinct
> difference between the rising and falling edge in simulation and
> measurement. Even when taking into account probe loading and
> oscilloscope filtering, the simulated edges cannot match the
> measurement. The step in the clock output (caused by transmission line
> loading and reflected wave effects), visible in the simulation, is not
> seen on the oscilloscope screen. I tried to modify the waveform, which
> by the way is normalised in Quad, but with unsatisfactory results.
>
> Tested are:
>
> - the waveform supplied with the clock model
> - a straight line
> - a sinusoidal form
> - no waveform at all (deleted)
>
> Especially the straight line shows a sharp step, the worst of all. The
> last one (no waveform at all) shows the least visible step, and thus
> is the best (with respect to the rising/falling edge form). Thus one
> would ask oneself, why taking the trouble of including those
> waveforms?
>
> Is there someone with a similar experience?
> Or does someone have some recommendations?
>
>
> Best Regards
>
> Alex Hilbers
> ahilbers@tulip.nl
>
>-- End of excerpt from "Hilbers, Alex"
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Received on Fri Feb 28 04:34:13 1997
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