Subject: RE: [IBIS-Users] (lv)pecl
From: Tom Dagostino (tom@teraspeed.com)
Date: Mon May 12 2003 - 09:41:02 PDT
Erik
Fred is right that for an ECL model that the voltage range that has to be
characterized is over the 0 to Vcc - 2V range in the table. I like to see
at least the active region between 0 and Vcc modeled. There are some ECL
parts that will not be adequately characterized by only going from 0 to
Vcc - 2V. If I remember correctly ON Semi makes some ECL line drivers that
have about twice the swing of normal ECL.
Fred, the garbage Erik referred to was multiple lines in the tables that
have the same voltage values and zero current. I've seen models with this
before but I don't remember the cause of it.
Yes, IBIS likely goes too far into the clamp regions for characterization.
If your clamp currents are extreme it is likely that the clamp diodes have
not been properly characterized in their SPICE models. If you are seeing
more than a few amperes in the clamps you can assume the intrinsic
resistance of the diodes, the metal, etc. have not been fully characterized.
To eliminate this try adding a few hundred milli Ohms in series with the
clamps to bring the currents down to a more realistic level.
Tom Dagostino
Teraspeed Consulting Group LLC Teraspeed Consulting Group LLC
2926 SE Yamhill St. Device Modeling Division
Portland, OR 97214 13610 SW Harness Lane
Beaverton, OR 97008
http://www.teraspeed.com 503-430-1065
tom@teraspeed.com
-----Original Message-----
From: owner-ibis-users@server.eda.org
[mailto:owner-ibis-users@server.eda.org]On Behalf Of
erik.van.der.ven@philips.com
Sent: Monday, May 12, 2003 1:44 AM
To: ibis-users@server.eda.org
Subject: Re: [IBIS-Users] (lv)pecl
Dear Fred,
Thank you for your reply. About the garbage; I explained it in an email I
just sent (directed to Tom).
The s2ibis program does not generate IV- tables from 0-2.2V, but the
program that has been modified by my collegue does do this (apart from the
"garbage" that both programs produce).
Is this range enough? According to Tom it should be -3.3-6.6V. Where is
this range for ECL/PECL defined? I cannot find it in the specification.
When the voltage is out of the normal operating range the currents can be
very high, even so high that the transistor models are not valid anymore.
What is the use of specifying these currents? Can they be left out? If not,
what is done with this information.
I have the same question for the clamp currents. The output can be
disabled, so this is a kind of tri-state (not really high impedant). Also
here the currents are unrealistically high. What is done with this
information? Why must it be specified? The PECL voltage swing is such that
even a fully reflected signal will not cause the output to be outside the
supply range.
With kind regards,
Ir. Erik van der Ven
Room DB1032
Business Line Networking Infrastructure
Philips Semiconductors BV
Gerstweg 2
6534 AE Nijmegen
The Netherlands
Phone: +31-24-3534334
Fred Balistreri <fred@apsimtech.com>
Sent by:
fred@interjet.apsimtech.com
05/09/03 07:10 PM
To: Erik van der Ven/NYM/SC/PHILIPS@EMEA2
cc:
Subject: Re: [IBIS-Users] (lv)pecl
Classification:
Erik, you need to define what convention you are
using when you say voltage range. Remember that
for ECL and PECL both the pullup and pulldown
reference is the same. If the voltage range
you refer to is the IBIS Vtable then your
range is not correct. Under the IBIS conventions
for ECL or PECL type Vtable= Vcc - Vout.
This is true for both pullup/pulldown for PECL/ECL.
IBIS further explains that for ECL, PECL the
range should be VCC - 2.2 volts. Under the
IBIS rules then the range should always be
0 - 2.2 volts for both pullup and pulldown.
Note that 0 really means 3.3 at the output
for your case and 2.2 really means 1.1 at the
output.
I don't quite understand your problem. You state
garbage. It's probably not quite descriptive
enough to understand your issue. Although the
meaning is clear.
Best Regards,
erik.van.der.ven@philips.com wrote:
>
> Part 1.1Type: Plain Text (text/plain)
--
Fred Balistreri
fred@apsimtech.com
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