The other thing you might want to add to the impedance you determined by
examining the [Pullup] and [Pulldown] I-V curves, is the package
resistance. It ought to be relatively insignificant, but that doesn't
preclude someone from being "creative" by manipulating the IBIS model's
output impedance using a larger package resistance than that
attributable to the package alone.
Package resistance appears in two places, a Typ/Min/Max default value
(R_pkg) that applies to all pins, and a pin-by-pin override (R_pin). If
the latter is absent ("NA"), the former should be used.
At higher frequencies, of course, parasitics such as C_comp, C_pkg,
C_pin, L_pkg, and L_pin alter the output impedance that you get from the
I-V curves alone.
As you probably know already, IBIS files can contain multiple models
(for each buffer type of the IC it represents), and you have to be
careful to separate the file into each [Model] first, so that you don't
inadvertently apply a parameter from one [Model] to a different [Model].
Regards,
Andy
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List archives are viewable at:
http://www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu