In normal usage, the actual load (i.e., traces and other devices) connected to an output device creates a rather complex, frequency dependent load. It's highly unlikely that the output device was characterized with that kind of load. While there may not be a guarantee, one should expect that an IBIS model would produce reasonably good results with such complex loads as well as simple R/C loads (with not unreasonable values), even though they weren't use to generate the VT curves. Anyway, most VT curves are established with resistive loads (zero capacitance), which "never" happens in practice. The VT curves may be used only to "calibrate" the simulator's representation of the ouput device, not to generate actual waveforms. Regards, Andy > A coworker wants to simulate what affect connecting > different capacitors to the output pin of a device > would have on its transtion time. He doesn't have > access to spice models and he asked me if he could use > IBIS models. I told him that since the models are > characterized under a given load, changing that load > in simulation may not give him very accurate results. > Was I correct, or will the simulator use the values of > the IV curves and test fixture to accurately skew the > rise and fall times specified in the VT curves? |------------------------------------------------------------------ |For help or to subscribe/unsubscribe, email majordomo@eda.org |with just 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 email a written request to ibis-request@eda.org. | |IBIS reflector archives exist under: | | http://www.eda.org/pub/ibis/email_archive/ Recent | http://www.eda.org/pub/ibis/users_archive/ Recent | http://www.eda.org/pub/ibis/email/ E-mail since 1993Received on Mon Jan 30 19:53:24 2006
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