A extra comment to this discussion. The cell technology has changed a lot since the original IBIS specs., likewise has the levels and numbers of power supplies. The '-Vdd to +2Vdd' should not be used headless for modern drivers, but be adjusted to the 'usage/design' of the individual cell. Last year I created some IBIS models for a cell library with the following characteristics * 3.3 V IO voltage supply * 5 V tolerant inputs, max input voltage is 5.5 V * 2.5 V internal ESD/clamp voltage supply. I.e. the driver pad is connected to the internal clamp voltage through 4 diodes. Using the '-Vdd to +2Vdd' could give 3 different options -3.3 V to +6.6 V -5 V to + 10 V -2.5 V to + 5 V Using the '5 V tolerant' level as basic for the range for the clamp curves would not be wise and neither possible to simulate, nor measure. With some difficulties, the models were created with -3.3 V to 6.6 V for the clamp curves. Regards /Henrik G Madsen ________________________________ From: Mirmak, Michael <michael.mirmak_at_.....> Date: Fri Feb 16 2007 - 01:03:35 PST Sudarshan, The idea is to cover doubled-voltage reflections from unterminated lines. For example, PCI bus receivers do not terminate but the bus instead functions using reflected-wave switching. As a result, an old-style 5 V PCI device, if used in a system with little line loss, could drive a 5 V signal and see it reflected back to itself at 10 V off the unterminated end of the line. If you look at the original 5 V PCI specification, the buffer overshoot section allows for something approaching 11 V, if memory serves. Lower speeds of USB have similar tolerance rules. You are correct that more modern drivers, particularly in low-voltage, low-swing serdes terminated environments, are less likely to encounter such harsh conditions. - Michael Mirmak Intel Corp. Chair, EIA IBIS Open Forum ________________________________ From: owner-ibis-users@server.eda.org [mailto:owner-ibis-users@server.eda.org] On Behalf Of Sudarshan Honnudike Sent: Friday, 16 February, 2007 9:16 To: Mirmak, Michael Cc: ibis-users@server.eda.org Subject: [IBIS-Users] RE: Tolerant IO cell's Supply voltage range.? Thanks Michael for the clarifications. But still i want to know what is the point in providing such big ranges of voltage if the cell doesn't work at that voltages. ? Because for a 5V tolerant cell, maximum it can tolerate 5V. So what is the intention of providing the voltage range from -5V to +10V. Definitely at such high voltages the cell will breakdown. Is there any use of providing such tables in application ? The reason for choosing -Vdd and +2Vdd is to take care of short and open circuit conditions. But under those conditions , cell will anyway will not work. So what the whole idea behind it ? Best Regards, Sudarshan HN NXP Semiconductors/CTO /PLT C-4, Manyata Tech Park, Nagawara Bangalore-560 045 , India. Ph:+91-80-40267073 Fax: +91-80-4026 7855 seri:sudarsha@inpsblr E-mail: sudarshan.honnudike@nxp.com "Mirmak, Michael" <michael.mirmak@intel.com> 2007-02-14 11:27 PM To "Sudarshan Honnudike" <sudarshan.honnudike@nxp.com> <ibis-users@server.eda.org> cc Subject RE: Tolerant IO cell's Supply voltage range.? Classification Sudarshan, You are indeed correct. For 5 V tolerant buffers, the clamp tables would cover a range based on a 5 V supply, to withstand any incoming high-voltage signals. The [Pullup] and/or [Pulldown] tables would cover a range based on the 3.3 V supply. - Michael Mirmak Intel Corp. Chair, EIA BIS Open Forum ________________________________ From: Sudarshan Honnudike [mailto:sudarshan.honnudike@nxp.com] Sent: Monday, February 12, 2007 21:56 To: ibis-users@server.eda.org; owner-ibis-users@server.eda.org Subject: Tolerant IO cell's Supply voltage range.? Hello All, I want to know what should be the voltage range for the tolerant cells for I-V curves like [Gnd Clamp], [Power Clamp], [Pull up] & [Pull down]. I read it from one of the presentation that, say for a 3.3 V functional 5 V tolerant cell the voltage range is from -5V to +10V. Do what curves this range applies ?. I dont think this range has to be applied for [Pull u] and [Pull down] curves as these are basically driver characteristics and maximum they can operate under 3.3V. So is it only for Clamp curves ? Please let me know your answers. Best Regards, Sudarshan HN NXP Semiconductors/CTO /PLT C-4, Manyata Tech Park, Nagawara Bangalore-560 045 , India. Ph:+91-80-40267073 Fax: +91-80-4026 7855 seri:sudarsha@inpsblr E-mail: sudarshan.honnudike@nxp.com -- 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 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 Wed Feb 21 08:06:49 2007
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