RE: [IBIS-Users] RISING n FALLING

YY,
 
Thank you for your message.  
 
To respond to your first question, why do you expect to a rising
waveform table using a Vcc-terminated load to start at 0 V?  For a
typical push-pull buffer structure, a [Rising Waveform] into a load to
Vcc (assuming your Vcc = 3.0 V) characterizes the *pulldown turning
off.*  The [Rising Waveform] table in this case should end at the
termination voltage (which yours does) and start at a voltage determined
by the voltage divider between the Ron of your buffer's pulldown and the
R_fixture load. 
 
If you want a [Rising Waveform] which starts at 0 V, look at or generate
a [Rising Waveform] table which uses a ground-terminated load.  Such a
table would characterize the *pullup turning on.*
 
Your second question is much harder to answer without additional data.
Are the [Pulldown] and [Pullup] tables *entirely* zero?  If so, did you
enable your buffer's outputs to drive when you collected the data?  If
not, do your [POWER Clamp] and [GND Clamp] tables include valid data?
Were the clamps included in your circuit when you collected the
[Pulldown] and [Pullup] data?  Did you perform any clamp subtraction on
your [Pullup] and [Pulldown] data before including it in your IBIS file?
I would advise checking your circuit simulation setup to ensure that it
makes sense for the data you are trying to collect.
 
- Michael Mirmak
  Intel Corp.
  Chair, EIA IBIS Open Forum

________________________________

From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On
Behalf Of lau yy
Sent: Wednesday, August 03, 2005 5:52 PM
To: ibis-users@eda.org
Subject: [IBIS-Users] RISING n FALLING


Dear ALL,
 
Recently, I building a model and I face aproblem. For my I/O pin, my
rising and falling data show as below
 
[Rising Waveform]
R_fixture = 50.0000
V_fixture = 3.0000
V_fixture_min = 2.7000
V_fixture_max = 3.6000
| time           V(typ)              V(min)              V(max)
|
  0.000S          1.8460V             2.0370V             1.7920V
   2.0000nS       2.1155V             2.1130V             2.2380V
   4.0000nS       2.7760V             2.4780V             3.3855V
   6.0000nS       2.9727V             2.6540V             3.5830V
   8.0000nS       2.9970V             2.6930V             3.5985V
  10.0000nS       2.9990V             2.6975V             3.5995V
  12.0000nS       2.9990V             2.6990V             3.6000V
  14.0000nS       3.0000V             2.6990V             3.6000V
 
Q1 : It looks like not starting from around 0V. And same as Falling, it
wont fall lower than 1.8V. Is that means my model wrong or the
input/output voltage range for the product is small? 
 

Q2: My pullup and pulldown data is started from 0A. But it pass the
ibischk3.
 
[Pulldown]
| voltage     I(typ)              I(min)              I(max)
|
  -3.0000       0.000A              0.000A              0.000A
  -2.8000       0.000A              0.000A              0.000A
  -2.6000       0.000A              0.000A              0.000A

 
Thanks
 
 
rdgs
yylau
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