Re-sending with updated attachment Hi, I am making IBIS models for LVDS (low voltage differential signal) IO buffer. To model an LVDS buffer I created the following test circuit, assigned the generated IBIS model to both buffers, set one buffer as inverted output. *Problem:* In the image below the YELLOW waveform is what I saw and the PURPLE waveform is what I expected to see. YELLOW = IBIS model PURPLE = Spice ( reference ) model Here is combined pullUp (yellow) and pullDown (green) IV curves (actually it is spice curves from which IV tables were derived): Lets assume that simulator tries to find operational point for LVDS buffer driving high. Then for the non-inverted buffer a point (Vp, Ip) will be taken from pullUp table, for the inverted buffer a point (Vn, In) from pullDown table, the following conditions should be satisfied: Ip = In, Vp - Vn = Ip*50. On the image above it is seen that there are 2 points satisfying the condition: Vp =~ 1.45V and Vp =~ 2.2V. Seems that something like that happened during simulation and simulator got to the second point. (BTW, there are 60 points for the region 0.9 - 1.6V and 10 points for the region 1.6-2.5V in the IBIS model IV tables). *Question:* What can be done to resolve this situation? Should IV tables or another IBIS structures be modified and how? I am making *ibis ver. 4.2* models. Thanks, Andrey On 09/18/2013 06:33 PM, Andrey Babintsev wrote: > > *Warning: This message has had one or more attachments removed > (fail.min.png). Please read the "EDA-Attachment-Warning.txt" > attachment(s) for more information.* > > Hi, > > I am making IBIS models for LVDS (low voltage differential signal) IO > buffer. > To model an LVDS buffer I created the following test circuit, assigned > the generated IBIS model to both buffers, set one buffer as inverted > output. > > > *Problem:* > In the image below the YELLOW waveform is what I saw and the PURPLE > waveform is what I expected to see. > > YELLOW = IBIS model > PURPLE = Spice ( reference ) model > > Here is combined pullUp (yellow) and pullDown (green) IV curves > (actually it is spice curves from which IV tables were derived): > > > Lets assume that simulator tries to find operational point for LVDS > buffer driving high. Then for the non-inverted buffer a point (Vp, Ip) > will be taken from pullUp table, for the inverted buffer a point (Vn, > In) from pullDown table, the following conditions should be satisfied: > Ip = In, Vp - Vn = Ip*50. On the image above it is seen that there are > 2 points satisfying the condition: Vp =~ 1.45V and Vp =~ 2.2V. Seems > that something like that happened during simulation and simulator got > to the second point. (BTW, there are 60 points for the region 0.9 - > 1.6V and 10 points for the region 1.6-2.5V in the IBIS model IV tables). > > *Question:* > What can be done to resolve this situation? Should IV tables or > another IBIS structures be modified and how? I am making *ibis ver. > 4.2* models. > > Thanks, > Andrey -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. -------------------------------------------------------------------- |For help or to subscribe/unsubscribe, e-mail mikelabonte@eda-stds.org |or ibis-request@eda-stds.org | |IBIS reflector archives exist under: | | http://www.eda-stds.org/ibis/email_archive/ Recent | http://www.eda-stds.org/ibis/users_archive/ Recent | http://www.eda-stds.org/ibis/email/ E-mail since 1993Received on Wed Sep 18 07:33:25 2013
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