Date: Fri Oct 12 2007 - 13:07:21 PDT
Hi Tim, Sorry for my late reply. I just now had a chance to look at the file you provided. Every IBIS package model has a unique combination of benefits and limitations. Lynne mentioned one of the drawbacks, which is unfortunately common to many of the IBIS package models. Because of this assumption, an IBIS model should only have one logical "pin" for power and one for ground. Multiple RLCs for a single net are dangerous. The major benefit of this model is that coupling can be defined between pwr/sig/gnd. Because of this feature, the coupled RLC matrix format is the best official IBIS package model format for PCB designers wanting to perform system-level SSO analysis. (I emphasize official because many package designers commonly use other types of package models.) However, the model has to be correctly generated and implemented in simulation. Note the attached picture; it shows one of the dangers about many IBIS models. The trouble is in the "ground" pin. See how it can have a capacitance term? That's bad. You may or may not know what the PCB simulator will do with that term. The picture shows how some tools use an "ideal ground" reference node that is different from the GND node shown in the picture. Does your simulator connect "ideal ground" and GND? You need to know this if you want to use models that contain C terms for ground nets (like the model you attached to your original email). This is also dangerous. Thankfully, there are other ways to generate the model that do not require the use of "ideal ground". I prefer those techniques much better because then you do not have to worry as much about what the simulator does with "ideal ground" and GND. In summary, be suspicious of IBIS models that have either of the following: 1) Multiple pin RLCs for a single net [Pin] signal_name model_name R_pin L_pin C_pin 1 VDD POWER 1.1 1.3 1.5 2 VDD POWER 1.2 1.4 1.6 2) RLC entries for "ground" nets 3 VSS GND 1.7 1.8 1.9 Either of these can cause incorrect results in some tools. Thanks, Sam _____ From: owner-ibis-users@server.eda.org [mailto:owner-ibis-users@server.eda.org] On Behalf Of Lynne D. Green Sent: Monday, October 01, 2007 9:42 AM To: 'Ibis Model'; 'Server EDA' Subject: RE: [IBIS-Users] Package Modeling in IBIS -Matrix format Hello, Tim, The IBIS specification has a chapter on the PKG format. The major limitation with PKG format is that it only supports pin-to-pad (no branching). Best regards, Lynne "IBIS training when you need it, where you need it." Dr. Lynne Green Green Streak Programs http://www.greenstreakprograms.com 425-788-0412 lgreen22@mindspring.com _____ From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf Of Ibis Model Sent: Monday, October 01, 2007 2:54 AM To: Server EDA Subject: [IBIS-Users] Package Modeling in IBIS -Matrix format Hi, I have come across this IBIS model with the respective package model file (in .pkg format) and it seem to me that the package information for all RLC is presented in a matrix format. Is there any available document that can explain how this numbers can be useful to the user as well as how they play a role in the simulation? Else, can IBIS open forum helps to explain how these values are being presented and how can the simulation tools use these information to verify whether the simulator already included the package model. I will be glad if you can point me to any document related to this matrix RLC package modeling. Appreciate your reply on this. Please find attachement the package model file. Regards Tim _____ Take the Internet to Go: Yahoo!Go puts the Internet <http://us.rd.yahoo.com/evt=48253/*http:/mobile.yahoo.com/go?refer=1GNXIC> in your pocket: mail, news, photos & more. -- This message has been scanned for viruses and dangerous content by <http://www.mailscanner.info/> MailScanner, and is believed to be clean. -- This message has been scanned for viruses and dangerous content by <http://www.mailscanner.info/> MailScanner, 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 majordomo@eda-stds.org |with the appropriate command message(s) in the body: | | help | subscribe ibis <optional e-mail address, if different> | subscribe ibis-users <optional e-mail address, if different> | unsubscribe ibis <optional e-mail address, if different> | unsubscribe ibis-users <optional e-mail address, if different> | |or e-mail a request to ibis-request@eda-stds.org. | |IBIS reflector archives exist under: | | http://www.eda-stds.org/pub/ibis/email_archive/ Recent | http://www.eda-stds.org/pub/ibis/users_archive/ Recent | http://www.eda-stds.org/pub/ibis/email/ E-mail since 1993
