Subject: Re: [IBIS-Users] damped oscillations in V-T curve
From: Ingraham, Andrew (a.ingraham@ieee.org)
Date: Fri Jun 27 2003 - 08:53:16 PDT
I don't know if this has any bearing on this particular issue, but ...
You noted that the discrepancy was with the first peak, implying that the damped oscillations that followed it were not that bad. This implies a nonlinear effect.
It should also be noted that PECL outputs are very nonlinear, and this is most evident on falling edges.
I wonder how well Spectre handles that much nonlinearity.
Likewise, it might also be that IBIS models, or the HSPICE implementation of IBIS models, do not function all that well when there is that much nonlinearity.
Check to see whether HSPICE has an option to make it use more than just the first V-T curve. Also try changing the order of the V-T curves in the model, to force it to use the R_fixture=70 ohm curve.
Regards,
Andy
----- Original Message -----
From: erik.van.der.ven@philips.com
To: ibis-users@eda.org
Sent: Thursday, June 26, 2003 05:43 AM
Subject: [IBIS-Users] damped oscillations in V-T curve
Hello,
In my V-T curve I see a damped oscillation in the falling waveform (diff PECL).
When I do a HSPICE simulation with different load resistances I observe that the amplitude of the first peak increases dramatically while this is not the case in a simulation of the original buffer in Spectre.
What should I do to model this behaviour correctly. And what causes this increase in amplitude?
With kind regards,
Ir. Erik van der Ven
Room DB1032
Business Line Networking Infrastructure
Philips Semiconductors BV
Gerstweg 2
6534 AE Nijmegen
The Netherlands
Phone: +31-24-3534334
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