Subject: RE: [IBIS-Users] Vinh for Differential Part
From: Timothy Coyle (Timothy.Coyle@nsc.com)
Date: Fri Dec 06 2002 - 10:12:42 PST
I think the problem is that the Vth and Vtl defined for the differential
input is being applied to the single-ended signal, and
not the differential signal. A vdiff of +/- 100mV of the common mode input
voltage only applies to the differential signal. For the single-ended
signal,
I believe the threshold should be +/-100mV from what ever voltage the
other pin is tied too. For example, VA VTH is = VB + 0.1V, VTL = VB -
0.1V.
But if I have Vdiff defined, these values shouldn't be used at all. And if
I don't have Vdiff defined, I do not think that these threshold values are
going
to be used for the differential signal. It might also be irreverent because
is there any situations when one would want to do any timing measurements
on the single-ended signal rather than the differential signal? If not,
then the parser and EDA tools need to be informed to correct this.
Regards,
Tim
|---------+---------------------------->
| | hazem@qualim.com |
| | |
| | 12/06/2002 12:27 |
| | PM |
| | |
|---------+---------------------------->
>------------------------------------------------------------------------------------------------------------------------------|
| |
| To: Timothy Coyle/Americas/NSC@NSC |
| cc: ibis-users@server.eda.org@Internet |
| Subject: RE: [IBIS-Users] Vinh for Differential Part |
>------------------------------------------------------------------------------------------------------------------------------|
Well, your observation is right; the parser will not allow not putting
Vinh and Vinl for an input buffer even if the existence of Vdiff will
override the Vinh/Vinl thresholds.
For levels 1.0 ~1.4 with Vdiff=0.1V, the buffer will switch if you apply
differential voltage of at least 100mV around the common mode input
voltage and not 1.1V and 1.3V
I hope it helps,
BR,
Hazem Hegazy, M.Sc.
IBIS Modeling Engineer
QualiM
http://www.qualim.com/
Phone: (+20) 106052154
E-mail: hazem@qualim.com
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