All
BIRD113.1 is up for discussion of Friday, October 1.
Some Weak tie-up or tie-down components look resistive. Others
formed from internal FET devices look more like constant
current sources over most of the range.
This distinction makes a difference if one is to use the Weak_*
information to determine the overall state of a particular
net.
We suggest adding Weak_I as an optional alternative to Weak_R.
The rules would be:
Weak_I and Weak_V (for supply reference information)
or
Weak_R and Weak_V
The current conventions for Weak_I are:
Positive for tie-down (similar to [Gnd Clamp]
Negative for tie-up (similar to [Power Clamp]
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Example 1.
Vdd is 5 V. Net has one device with 100 k to GND, and the other with
100 k to Vdd.
The resistor divider DC voltage is estimated to be 2.5 V and
state of the net is ambigous.
Example 2.
Same situation, except the device with a FET tie-up device is better
looks more like a -50 uA current source over most of its
range (instead of a 100 k resistor)
The DC output state is held High at 5 V.
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So the approximate shape has an impact on the calculated
DC state.
Bob
-- Bob Ross Teraspeed Consulting Group LLC Teraspeed Labs 121 North River Drive 13610 SW Harness Lane Narragansett, RI 02882 Beaverton, OR 97008 401-284-1827 503-430-1065 http://www.teraspeed.com 503-246-8048 Direct bob@teraspeed.com Teraspeed is a registered service mark of Teraspeed Consulting Group LLC -- 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 Mon Sep 27 19:51:39 2010
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