Hi Using ½ of R_diff to ground and simulating the V-T char dos not settle the outputs at required levels. actually according to the termination as shown in attachment the rl =50ohm connected from each differential output to common cap and cap is connected to Vcm_rx w .r.t gnd. How to divide this in to half? And get ibis model correct? What values to be used in the Rfixture , vfixture, Rref ,Vref, Vmeas ,etc in .s2i file Regards Saravanan.G From: Lynne Green [mailto:lgreen22@mindspring.com] Sent: Friday, May 09, 2014 10:39 PM To: Saravanan Ganesh; ibis-users@eda.org Subject: Re: [IBIS-Users] full differential buffer IBIS modeling ---clarification Dear Saravanan, A differential buffer in IBIS 3.2 requires two buffer models, one for each output. To use s2ibis3: -Use the SAME load to ground for EACH output. - Do not use a differential resistor between the two outputs. Use 1/2 of R_diff to ground. - Run s2ibis3 once, using the inverting output pin, and create BUFFER1. Run it again for the non-inverting output pin, and create BUFFER2. Note that no other changes are made between the two runs. - In the models, be sure to label the output type to indicate BUFFER1 is inverting and BUFFER2 is non-inverting. For simulation, assign BUFFER1 to the inverting pin and BUFFER2 to the non-inverting pin. Under [Diff Pin], list the buffers with ZERO time offset (the time offset is captured in the V-t tables). At least one simulation, with R=Rload, should be used to test the model before releasing it for use, another with a different R is recommended.. Hope this helps. PS: if you plan do this often, you can modify the s2ibis3 source to capture both outputs in just one run of s3ibis3. Not sure why no-one has shared their modification with the IBIS Open Forum. Cheers, Lynne Green retired On 5/9/2014 8:20 AM, Lance Wang wrote: Saravanan, The first, s2ibis3 can be used for simple single-end buffer only. It might not be satisfied for differential buffers. The second, R_load in s2i is the same as R_fixture in the IBIS file. The third, full/true differential pair buffer IBIS extraction will not be handled by s2ibis3 correctly. Another word, you will never be able to get correct IBIS models thru s2ibis3 for your full differential buffers. Hope this helps. Lance Wang IO Methodology Inc. 978-266-8981 SimDE MODEL, the best IBIS modeling tool in the market. http://www.iometh.com From: Saravanan Ganesh <Saravanan.Ganesh@onsemi.com<mailto:Saravanan.Ganesh@onsemi.com>> Date: Friday, May 9, 2014 at 9:55 AM To: "ibis-users@eda.org<mailto:ibis-users@eda.org>" <ibis-users@eda.org<mailto:ibis-users@eda.org>> Subject: [IBIS-Users] full differential buffer IBIS modeling ---clarification Hi I want to brief on the R_load I am using I am creating IBIS model (Version 3.2) of a full differential buffer . I have also connected the termination shown in "diffbuff_termination.png" in differential buffer schematic. Even though I have connected the required termination in schematic itself , the .s2i file need R_load value to be supplied. Therefore I have used a High value resistor (R_load=100G ohm) in .s2i file. Hyperlinx "Check file for IBIS spec conformance" gives following error ... ERROR: Model OUTPUT_DIF: The [Rising Waveform] with [R_fixture]=1e+011 Ohms and [V_fixture_max]=0.22V has MAX column DC endpoints of 0.08V and 0.31v, but an equivalent load applied to the model's I-V tables yields different voltages ( 0.08V and 0.35V), a difference of 0.01% and 16.09%, respectively. What could be wrong? What can I do to get rid of these errors and warnings? Please mail me if any more clarification required ,Waiting for your replies. Thanks and regards Saravanan.G From: Saravanan Ganesh Sent: Thursday, May 08, 2014 8:04 PM To: 'ibis-users@eda.org<mailto:%27ibis-users@eda.org>' Subject: full differential buffer IBIS modeling Hi I am creating IBIS model (Version 3.2) of a full differential buffer . I have also connected the termination shown in "diffbuff_termination.png" in differential buffer schematic. Therefore I took R_load = 100G ohm in .s2i file, so that only load in schematic are effective. Hyperlinx "Check file for IBIS spec conformance" gives following error ... ERROR: Model OUTPUT_DIF: The [Rising Waveform] with [R_fixture]=1e+011 Ohms and [V_fixture_max]=0.22V has MAX column DC endpoints of 0.08V and 0.31v, but an equivalent load applied to the model's I-V tables yields different voltages ( 0.08V and 0.35V), a difference of 0.01% and 16.09%, respectively. What could be wrong? What can I do to get rid of these errors and warnings? Thanks and regards Saravanan.G -- This message has been scanned for viruses and dangerous content by MailScanner<http://www.mailscanner.info/>, and is believed to be clean. -- This message has been scanned for viruses and dangerous content by MailScanner<http://www.mailscanner.info/>, and is believed to be clean. -- 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 Tue Jun 10 23:39:37 2014
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