Date: Fri Feb 29 2008 - 11:07:32 PST
Muniswara, Looks like your V-t curve has an unnecessarily long dead zone at its beginning. It doesn't start switching for almost 400 ps. I would suggest to shift the V-t curve to the right so that it will begin its transition closely after t=0. Beware, you need to do this so that each V-t curve of the same buffer is shifted by the same amount and none of them get chopped off (or start before t=0). This will also effect your 2nd problem, the IBIS waveform will go to the left by the same amount you are shifting your V-t curves in the IBIS model. Arpad ------------------------------------------------------------------- ________________________________ From: Muniswara Reddy Vorugu [mailto:Muniswarareddy.Vorugu@arm.com] Sent: Thursday, February 28, 2008 11:43 PM To: ibis-users@eda.org; ibis-info@eda.org; ibis@eda-stds.org; michael.miramak@intel.com; Muranyi, Arpad Cc: Sivaramakrishnan Subramanian; Vivek kumar Singh; Nidhir Kumar Subject: please validate the VT waveform Hi, Please, help me in resolving following issues faced by me in validating IBIS model for LVDS buffer. ISSUE1 The figure below is the Rising waveform of an LVDS buffer. This buffer operates at 850MHz Frequency, ie.., Time period of 1.176ns. In Section 5.4.2 V-T Table Windowing of COOKBOOK -V4 I have seen the following statements. 1 The transient portion of the waveforms should start and finish within the time dictated by the highest frequency of the buffer (one-half of the period)( here it is 0.588ns). 2 For example, a signal that is anticipated to drive, at maximum, 100 MHz signals should have a V-T table duration no greater than 5 ns. From my understanding of first statement, the transient time (10% to 90% swing) is 0.200ns less than one-half of the periods (0.588ns). But, the V-T table duration is 1.00ns, which is greater than Half time period (0.588ns). I use Hspice to validate models. Can you please help me in validating this model? ISSUE2 IBIS is giving some delay compare to spice. Can you please comment on the reason for this. The VT table is captured with reference to input, as mentioned in COOKBOOK-V4. With regards, 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
