Hi everyone, I wanted to add a few more words on the differences between the two package models because I've had so many questions on it lately. Michael did me a big favor when he used the word "reference" in his response, and I thank him for it. :-) Defining that "reference" can be very tricky. We know that the [Pin] model cannot include coupling between pins. This restriction limits much more than just signal-signal coupling. Since no mutual terms exist, it's extremely difficult to correctly build a package [Pin] model for the POWER and GND nets of packages that use planes and have many pins. Stated another way, I do not recommend RLC entries in POWER and GND pins of the [Pin] model. No coupling forces many restrictions on the use of [Pin]. Ultimately it comes down to the realization that the [Pin] model should only be used for ideal PDS simulations. Since the POWER, GND, and signal interactions are extremely difficult (if not impossible) to accurately describe with the [Pin] syntax, the signal's RLC should represent the parasitics of the signal path AND its return path. Taking L as an example, it is the "loop inductance" of the signal net and its return path (L_loop=L_sig_parital+L_return_partial-2*L_sig_return_mutual). But what is the return path? Is it the GND net? The POWER net? One pin? Many pins? Due to this ambiguity, a common practice while extracting the [Pin] model in simulation is to ideally short all POWER and GND pins. This yields a [Pin] model that only has RLC entries for the signal pins, and these RLCs model the entire loop. But remember, this model is intended to be subsequently used in ideal PDS simulations only. But if the objective is to model the actual pwr/sig/gnd coupling relationships (typically for SSO analysis, with a realistic PDS and the actual return paths), then the .pkg matrix model is required. And don't forget the on-die capacitance in your SSO sims! :-) Thanks, Sam -----Original Message----- From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On Behalf Of Mirmak, Michael Sent: Sunday, April 22, 2007 5:51 PM To: Yasser Sabry; ibis@server.eda-stds.org Subject: RE: [IBIS] Question in R, L, & C Matrix Yasser, Thanks for your question. R_pin, C_pin, etc. are intended to represent package parasitics where coupling effects are not of interest. The matrix keywords, on the other hand, were added specifically to represent conductor-to-conductor package coupling for a component in an IBIS file. Are you trying to use discrete elements, including the [Pin] package parameters, to represent a coupled transmission line system? You may run into some trouble doing this directly. For example, C_pin is the capacitance of the pin by itself with respect to the (assumed) reference node for the circuit. However, the [Capacitance Matrix] is in Maxwellian format, where Cnn is the sum of the capacitance to the reference plus the mutual capacitance to the surrounding lines (i.e., as if all the other lines were grounded). Cnm is the mutual capacitance between lines n and m (and in Maxwellian format, the off-diagonal capacitances will be negative). Therefore, Cnn and C_pin would not be equivalent. The easiest way to obtain the matrix information would be to use a field solver on the package design and extract the matrices directly. - Michael Mirmak Intel Corp. Chair, EIA IBIS Open Forum -----Original Message----- From: owner-ibis@server.eda.org [mailto:owner-ibis@server.eda.org] On Behalf Of Yasser Sabry Sent: Sunday, April 22, 2007 7:28 AM To: ibis@server.eda-stds.org Subject: [IBIS] Question in R, L, & C Matrix Hi All, I have a question regarding [Resistance Matrix], [Inductance Matrix] and [Capacitance Matrix] Rnn, Lnn and Cnn are equivalent for R_pin, L_pin and C_pin. Right ? Rnm, Lnm and Cnm are connected in parallel between pin n and pin m. Right? -- Thank you and Best Regards, Yasser Sabry ------------------------------------------- Yasser Mohammed Sabry Device Modeling Team Analog/Mixed Signal - DSM Division Mentor Graphics Egypt Tel: (+202) 416 3613 Mob: (+2010) 1834833 Fax: (+202) 418 6945 E-mail: yasser_sabry@mentor.com ------------------------------------------- -- 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 -- 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 -- 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 1993Received on Tue May 1 15:34:46 2007
This archive was generated by hypermail 2.1.8 : Tue May 01 2007 - 15:36:53 PDT