Subject: RE: [IBIS-Users] (lv)pecl
From: erik.van.der.ven@philips.com
Date: Mon May 12 2003 - 00:36:49 PDT
Tom,
About the garbage lines:
I use s2ibis for model type output_ECL.
Voltage range has been left out (since this created a voltage source of
1.9V to the ground node in the spectre simulation files).
Pull-up and pull-down references have been set to 3.3V.
The result is an IBIS file that contains a pulldown-curve starting at 1.1V
and continuing up to 3.3V.
Then the next voltages are: 2.05, 9 times 0V and 3.3V. Most currents are
equal to the 3.3V current except for the max current, which is increasing
for every line (note that I filled in the typical values for the the min
and max cases).
The pull-up curve ranges from 0V to 2.2V and is then followed by 10 times
0V and 2.2V. The current for the 0V lines is always 0.000A, except for the
first one.
So I get some strange values and the range is from 0-2.2V instead of -3.3
to 6.6V.
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
"Tom Dagostino" <tom@teraspeed.com>
05/09/03 07:11 PM
Please respond to tom
To: Erik van der Ven/NYM/SC/PHILIPS@EMEA2
cc:
Subject: RE: [IBIS-Users] (lv)pecl
Classification:
Erik
In the old days (in the 60s) when Motorola first developed ECL They found
that running ECL from 0 to -5.2 volts worked better because the ground
planes on boards at the time was cleaner. ECL is referenced to the most
positive supply, thus a clean reference was important. In those days the
ground could have been a complete plane of the board but power was in many
cases distributed via traces on one of the layer. In today's modern
circuit boards both the power and ground are distributed in planes so this
is not an issue.
The voltage difference you see is not important. When you are running the
SPICE simulation you just need to connect the Vcc to 3.3 and the Vee to
ground to get the PECL model. Remember the 50 Ohm termination needs to be
connected to Vcc - 2 volts or 1.3 for the typical case when running the AC
simulations.
I do have concerns about the table range you are seeing. It should be
between -3.3 and +6.6 Volts for all the IV tables.
The simulator does several things with the data. First of all it will
check the data to ensure it is at least consistent, has not syntax issues,
etc. Then, for outputs, it builds a set of coefficients that describes
how the buffer transitions from pullup to pulldown and from pulldown to
pullup. This table is based on the VT waveforms and the IV curves.
The output impedance of the buffer is composed of the sum of the pullup or
pulldown IV table plus the power and ground clamps plus the component of
C_comp.
If the buffer is an input the the power and ground clamps are summed and
put in parallel with C_comp.
Because the model is designated ECL, the simulator makes one different
calculation for the pulldown table than it does for CMOS, see below.
What is the 10 lines of garbage you are seeing?
Hope that helps.
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: Friday, May 09, 2003 12:41 AM
To: ibis-users@server.eda.org
Subject: RE: [IBIS-Users] (lv)pecl
Tom,
Thank you for your reply. I am starting with a Spectre netlist. I have
tried s2ibis to make a model for LVPECL.
I noticed some differences. ECL has a supply of 0V (plus) and -5.2V (neg).
My circuit has a supply of 3.3V (plus) and 0V (neg).
The pulldown table ranges from 1.1V to 3.3V (the pull down reference has
been set to 3.3V, the pull-up reference as well), followed by ten lines of
garbage. A collegue of mine has changed to pragram a bit so the pull down
curve starts at 0V and ends at 2.2V (still followed by ten lines of
garbage).
Is this a correct range?
What does the simulator that uses the IBIS model do with the information
that it is an output-ECL model type? And how are the data tables
interpreted in conjunction with the ECL_model type?
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
"Tom Dagostino" <tom@teraspeed.com>
05/08/03 07:16 PM
Please respond to tom
To: Erik van der Ven/NYM/SC/PHILIPS@EMEA2
cc:
Subject: RE: [IBIS-Users] (lv)pecl
Classification:
Erik
What are you starting with? A SPICE description or are you going to make
the model from measurements? If you start with SPICE there is a spice to
ibis program that you can download from the ibis home page. If you are
starting from measurements then you will need a lot of equipment to make
the measurements. You will have to manually convert the measurements to
the ibis data.
Simulators use the output_ecl line to know how to handle ECL. In IBIS ECL
models are slightly different than standard CMOS or TTL drivers. In CMOS
or TTL the pulldown current is sunk into the ground plane and the pullup
current is sourced from the supply. With PECL both the pullup and
pulldown are sourced from the supply. So in PECL the pulldown is
referenced to the supply, not ground. The simulator needs to know this
when it is using the IV tables.
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: Thursday, May 08, 2003 12:04 AM
To: ibis-users@server.eda.org
Subject: [IBIS-Users] (lv)pecl
Dear all,
I think I mailed my question too early since I subscribed to the user
group at the same time. So I'll post it again, please see below.
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
----- Forwarded by Erik van der Ven/NYM/SC/PHILIPS on 05/08/03 09:03 AM
-----
Erik van der Ven
05/06/03 02:01 PM
To: ibis-users@eda.org
cc:
Subject: (lv)pecl
Classification: Unclassified
1. How can I make an IBIS model of a (LV)PECL model?
2. What does an IBIS simulator do with the model type information (like
output_ECL)?
Can anyone help me?
Thanks.
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
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