Subject: Re: [IBIS-Users] damped oscillations in V-T curve
From: erik.van.der.ven@philips.com
Date: Mon Jun 30 2003 - 01:49:57 PDT
Hello Andrew,
The oscillation/ringing is damped such that the next peaks become
negligible. I cannot image that these calculations are a problem for
Spectre. HSPICE has the possiblity to use 2 waveforms instead of one. But
I get a warning that it only uses one waveform, probably because it is not
needed for ECL according to the IBIS specification.
Do you have any idea how to deal with oscillations/ringing in general and
how simulators deal with it?
With kind regards,
Erik.
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
"Ingraham, Andrew" <a.ingraham@ieee.org>
Sent by:
owner-ibis-users@eda.org
06/27/03 05:53 PM
To: <ibis-users@eda.org>
cc: (bcc: Erik van der Ven/NYM/SC/PHILIPS)
Subject: Re: [IBIS-Users] damped oscillations in V-T curve
Classification:
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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