Subject: RE: [IBIS-Users] LVDS RECEIVER TERMINATION Question
From: Hassan Ali (Hassan.Ali@fidus.ca)
Date: Tue Jul 23 2002 - 09:31:13 PDT
Hi Peter,
I had the same situation a few months ago and I only had to go with an
adhoc solution.
Yes indeed most simulators do not have good support for differential
models with [R Series] termination. I ended up creating a single-ended
input buffer model (same for the P and N side) with no termination
between P and N sides. This only captured the clamping function.
In my simulation I had to recreate the terminated differential input
buffer by using two single-ended buffers (one for the P and one for the
N pin) with a termination resistor tied between them. The package
parasitics were also tied to the two pins. I manually changed the values
of the termination resistor and package parasitics to cover their
variation in the typical, minimum and maximum corners.
Probably there is a better solution, but that's what I did as a
quick-and-dirty work-around.
Regards.
Hassan.
Hassan Ali, Ph.D.
Signal Integrity Specialist -Talented, innovative designers
Fidus Systems Inc. -Highly competitive rates
Tel: (613) 828-0063 Ext.342 -Fixed-price business model
Fax: (613) 828-3113 -State-of-the-art design tools
http://www.fidus.ca -Customer-friendly attitude
-----Original Message-----
From: Peter LaFlamme [mailto:plaflamm@amcc.com]
Sent: Tuesday, July 23, 2002 9:01 AM
To: ibis-users@eda.org
Subject: [IBIS-Users] LVDS RECEIVER TERMINATION Question
Hi All,
I am tasked with creating an IBIS model for an LVDS receiver cell that
has an internal 100 ohm termination between the P and N nodes. I had
asked Bob Ross about this a while ago and as usual he was very helpful.
From his response I used the following
implementation:
|****************************************************************
| Component: LVDSRCV
|****************************************************************
|
[Component] LVDSRCV
[Manufacturer] AMCC
|
|
|
[Package]
| variable typ min max
R_pkg 1E-3 NA NA
L_pkg 1E-9 NA NA
C_pkg 1E-12 NA NA
|
[Pin] signal_name model_name R_pin L_pin C_pin
1 PAD lvdsrcv NA NA NA
2 PADN lvdsrcv NA NA NA
|
[Series Pin Mapping] pin_2 model_name function_table_group
1 2 rterm_100
|
[Diff_pin] inv_pin vdiff tdelay_typ tdelay_min
tdelay_max
|
1 2 0.2 0 0 0
[Model] rterm_100
C_comp 0.1pF 0.1pF 0.1pF
Model_type Series
|variable R(typ) R(min) R(max)
[R Series] 100 80 120
[Temperature Range] 25.00 125.00 0.00
[Voltage Range] 1.800 1.650 1.950
************************************************************************
****************
I was able to get the model past the IBIS checker but my simulations did
not show the 100 ohm terminator. I was using a tool which I believe does
not support this implementation (no need to mention names). I have seen
other implementations where I believe
a "Dynamic clamp" is used to model the termination behavior, but I am
unsure. Can anyone guide me to some reference material or weigh in with
your experience or help.
Thanks alot,
Peter
-- Peter LaFlammeApplied Micro Circuits Corp. System Applications Engineer 200 Minuteman Rd, 3rd Floor Andover, MA 01810
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