RE: [IBIS-Users] way to extract rising and falling waveform in differential cells

Are you terminating both sides of the differential driver when you extract
the VT waveforms? Many times differential buffers will not operate properly
if they do not have the proper termination on both outputs.

Tom Dagostino
Teraspeed Consulting Group LLC
503-430-1065
tom@teraspeed.com
www.teraspeed.com

  -----Original Message-----
  From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org]On Behalf
Of Akhilesh CHANDRA
  Sent: Sunday, December 19, 2004 7:40 AM
  To: Andrew Ingraham
  Cc: ibis-users@eda.org; Akhilesh CHANDRA
  Subject: Re: [IBIS-Users] way to extract rising and falling waveform in
differential cells

  Hello Andy,

   That means we can't make IBIS model that work at 1ghz. I think we can
make IBIS models at such high frequency. Now I put both rising and falling
database in my model and it is parsed by golden parser without any problem
but still result are not good at 622Mhz.
    Is this also problem from simulator. I am using eldo (AMS CADENCE)for
validation.

  Regards
  Akhilesh

  Andrew Ingraham wrote:

    Akhilesh,

    In the example you gave earlier, the simulation was at 250 MHz (2 ns
high and 2 ns low) and the waveform had just about reached the other state
when it was being switched again. Attempting to simulate this much faster
(622 MHz or 1 GHz), with IBIS, is probably doomed to failure because of
IBIS's limitations. This is sometimes known as "over-clocking" the IBIS
model, because the model hasn't reached the other state yet when it is being
clocked again in the other direction. Some simulators handle this situation
very poorly, so you could see very poor IBIS vs. SPICE correlation at such
faster frequencies.

    Regards,
    Andy

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Received on Sun Dec 19 13:36:22 2004