[ibis-macro] Re: Question on dividing up the Tx behavior between the AMI and analog portions of the model

  • From: James Zhou <james.zhou@xxxxxxxxxx>
  • To: "Terry.Chen@xxxxxxxxxx" <Terry.Chen@xxxxxxxxxx>, "DBanas@xxxxxxxxxx" <DBanas@xxxxxxxxxx>, 'IBIS-ATM' <ibis-macro@xxxxxxxxxxxxx>
  • Date: Mon, 12 Mar 2012 14:10:57 -0700

Hi David and Terry,

Both of your emails mentioned "analog IBIS model" and "IBIS-analog portion" 
represented by [Ramp] and/or [Rising/Falling Waveform] keywords in IBIS file.  
However, these "analog" IBIS models only take digital input signals,  as stated 
in IBIS Specification 5.0, page 71-72 and section 6b. The output of the 
"analog" IBIS model is not capable of tracking the amplitude changes in the 
input (other than a rise/fall transition). It would not make sense to feed the 
Tx AMI output to such digital inputs based on IBIS Specification 5.0.

If this approach of using [Ramp] and/or [Rising/falling Waveform] keywords to 
represent "analog IBIS model" is adopted by IBIS AMI flow, some clarification 
is needed on how to interpret and implement it.

Regards,
James Zhou
QLogic Corp.


From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] 
On Behalf Of Chen, Terry
Sent: Thursday, March 08, 2012 10:33 AM
To: DBanas@xxxxxxxxxx; 'IBIS-ATM'
Subject: [ibis-macro] Re: Question on dividing up the Tx behavior between the 
AMI and analog portions of the model

Hi David,

Actually I am interested in other's response to this question as well...

But, for the TX Driver I am currently modeling, I am doing exactly what you 
have prescribed and using the IBIS-analog portion as effectively an ideal step 
function (by setting my ramp with extremely high rise/fall dv/dt) and letting 
the step response filter inside my AMI model to shape my output waveform. Now, 
I am not sure if this is the "right" or "ideal" way to do it, but I am getting 
a reasonably good correlation in my Re-driver model with the actual lab 
measurements (the max jitter mismatch is < 8ps).

I hope this is at least an useful data point for you.

Regards,
Terry

From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] 
On Behalf Of David Banas
Sent: Thursday, March 08, 2012 1:15 PM
To: 'IBIS-ATM'
Subject: [ibis-macro] Question on dividing up the Tx behavior between the AMI 
and analog portions of the model

Hi all,

Is it customary to split up the Tx behavior, such that the FFE is modeled in 
the AMI model and the pulse shaper in the analog model?
Or, is there a different dividing line that has been identified as "best 
practice".
(Or, am I completely off in the weeds?)

The context for this question: I just managed to get good correlation between 
our latest Tx AMI model and the HSPICE model.
And then I realized that, having dumped all of the behavior into the AMI model, 
I would need to put an ideal step function into the V-T curves of the analog 
IBIS model. And I wasn't sure that would be a good idea. (I'm guessing that 
that would reek havoc in most simulators; is that correct?)

Thanks,

David Banas
Sr. Member Technical Staff
Altera<http://www.altera.com/>
+1-408-544-7667 - desk

Did you know Altera offers over 150 free online technical training 
courses<http://www.altera.com/servlets/searchcourse?coursetype=Online&WT.mc_id=t9_ot_mi_mi_tx_a_311>?
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