Subject: RE: [IBIS-Users] FW: Modelling an open drain driver
From: Henrik G. Madsen (hgm@vitesse.com)
Date: Mon Nov 25 2002 - 00:06:08 PST
An extra comment
Andrew Ingraham made the following comment, and I think he might be right.
"When the driver initially switches, and until the round-trip delay of the attached transmission line, the driver effectively sees a load of Rpullup in parallel with 60 ohms. After reflections on the transmission line have died out, it sees mostly just the Rpullup. So maybe you should provide waveforms for both values of R_fixture in the model file, and hope that the simulator knows how to figure it out and interpolate between them."
Currently, I just have the following 4 waveforms
[Rising waveform] 60 3.3 3.0 3.6 NA NA NA NA NA
[Falling waveform] 60 3.3 3.0 3.6 NA NA NA NA NA
[Rising waveform] 60 2.5 2.3 2.7 NA NA NA NA NA
[Falling waveform] 60 2.5 2.3 2.7 NA NA NA NA NA
The final value for the high voltage is dependent on Vpullup and Rpullup and not the transmission line.
As Andy suggest, should I also include some extra waveforms, which shows this situation and do the simulators have the ability to use these anyway?
******** Original circuit ********************
Vpullup is either 2.5V or 3.3V. Rpullup > 1.5k ohm
___Vpullup
|
|
/
\ Rpullup __________
OD driver / | |
\ ____________ | |
______.___|____| 60 ohm |_____| Receiver |
| |____________| | |
_| | |
-|_ |__________|
|
|
|__ VSS
|
-----Driver---|-----------normal use circuit--------------
_____________________________________
Henrik G Madsen
Sr. HW Engineer
Vitesse Semiconductor Corporation A/S
Ethernet Products Division
Hoerkaer 16, DK-2730 Herlev, DENMARK
Direct: +45 4485 5920
Phone: +45 4485 5900, Fax: +45 4485 5901
mail: hgm@vitesse.com
web: http://www.vitesse.com
_____________________________________
|------------------------------------------------------------------
|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 1993
This archive was generated by hypermail 2b28 : Mon Nov 25 2002 - 00:16:47 PST