Date: Wed Mar 05 2008 - 09:27:09 PST
Muniswara, You don't always need the series [Model] for a differential buffer. If there is no current flow between the pads, then it is OK not to have them. http://www.vhdl.org/pub/ibis/summits/feb04a/muranyi1.pdf On the other hand, if you don't include it when you need it, you may get miscorrelation, as shown on pg. 5 in the following presentation: http://www.eda.org/pub/ibis/summits/oct02/muranyi.pdf As far as I know, you can only detect the presence of pad-to-pad currents if you sweep the transistor level model's I-V curves in the double sweep mode as described in the cookbook. Once you reduced these I-V curves to just normal single ended models you won't be able to tell whether there was anything between the pins. I hope this helps. Arpad ----------------------------------------------------------------- ________________________________ From: Muniswara Reddy Vorugu [mailto:Muniswarareddy.Vorugu@arm.com] Sent: Sunday, March 02, 2008 5:24 AM To: ibis-users@eda.org; ibis-info@eda.org; ibis@eda-stds.org; michael.miramak@intel.com; Muranyi, Arpad Cc: Nidhir Kumar Subject: please validate the I-V table of the LVDS Buffer Hi, I am validating a differential driver, LVDS buffer. Sections 4.6.1 and 4.6.2 of the COOKBOOK-V4 are insisting on separating Differential current (Idiff) and Common mode current (Icom). Then differential current need to modeled as a series [model] : In my model, I did not find any series [model] key word. Please clear the following queries: 1: What will happen if differential current and common mode currents are not separated? 2: Is it possible to identify (seeing the I-V pull-up/pull-down Curve) that there exists of a resistor (series element) between the pads (pad+ and pad-) and not been modeled. I am attaching the I-V Curves. This Pull-up and Pull-down tables are generation with this algorithm: A1: The sum of potential at the output pads is equal to 2.4. (2 * 1.2) (Vpad+) + (Vpad-) = 2*Vref (here 1.2V) = ( Vref + DeltaV) + ( Vref - DeltaV) I(IVtable) =I(raw) - Iclamp A2: The clamp currents are measured with both the pads being at same potential. V(pad+) = V(pad-) Pull-down curve Pull-up curve related to VCC. Muniswara Reddy . V Design engineer, PIPD-IO group, Bangalore. -- IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you. -- 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
