[SI-LIST] Re: Correlation to lab measurement
- From: Scott McMorrow <scott@xxxxxxxxxxxxx>
- To: "Santangelo, Steven" <SSantangelo@xxxxxxxxxxxx>
- Date: Tue, 08 Jun 2010 10:33:06 -0400
Steven
It is most likely that the point at which you measuring is different
than the point that you displaying waveforms from in SpectraQuest. If
that is not the case, then it could be that your IBIS model is being
simulated as a discrete RLC, rather than a transmission line. Some
tools automatically convert the IBIS RLC package model into an
equivalent transmission line. If I remember correctly, other tools may
need a "nudge" to do this. SpectraQuest experts here should be able to
help you.
regards,
Scott
On 6/8/2010 10:22 AM, Santangelo, Steven wrote:
> Hi All,
>
>
> I'm trying to correlate some lab measurements to my simulations in
> Cadence PCB SI (SpectraQuest). I have a 400MHz unidirectional LVDS
> interface between two Xilinx devices that is terminated in 100ohms
> inside one of the devices. My lab measurements show a pretty good
> reflection occurring on the rising and falling edges of the waveform.
> I'm trying to determine if this is being caused by the ball to I/O pad
> trace length in the package (plus my BGA breakout). My simulation only
> shows a slight bend in the waveform rather than the non monotonic ring
> that I see in the lab. The bend does correlate well time wise (location
> on the edge) with the lab measurement. I don't really know much about
> the limitations of IBIS models so I'm wondering if some of the
> discrepancy could be due to that.
>
>
>
> FYI: I'm using the models that Xilinx "ibiswriter" puts out. The
> rise/fall times of the waveforms are in the neighborhood of 300pS.
>
>
>
> Thanks
>
>
> Steve
>
>
>
>
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--
Scott McMorrow
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