[ibis-macro] Response to my action item: on-die interconnect Touchstone to include a.c. behavior of final drive stage?

  • From: David Banas <DBanas@xxxxxxxxxx>
  • To: "'ibis-interconn@xxxxxxxxxxxxx'" <ibis-interconn@xxxxxxxxxxxxx>, "'ibis-macro@xxxxxxxxxxxxx'" <ibis-macro@xxxxxxxxxxxxx>
  • Date: Mon, 25 Feb 2013 16:37:01 -0800

Hi all,

With regard to the action item I took at last week's ICM meeting:

Find out if Altera's on-die interconnect Touchstone files include any of the 
driver's a.c. behavior.

The answer is:

No, they do not. They are a "pure" description of the actual passive physical 
structure lying between the drains of the final drive totem pole and the point 
of die attach. They are generated using 3D extraction tools, as opposed to 

In my discussion with my ICD folks, someone made a very interesting point:

The manufacturing variation of the on-die interconnect response characteristics 
is typically the result of physical dimension variance, which in turn is caused 
by the inherent tolerances of the photo-lithography process. Conversely, the 
variation in the driver output stage characteristics are most often primarily 
due to voltage, temperature, and process variation. So, if we were to include 
the driver output stage a.c. behavior in the Touchstone file representing the 
on-die interconnect, we would be hard pressed to adequately describe typ., min. 
and max. behaviors for the combined entity, and the range of validity of a 
Touchstone file so constructed might be very limited. (This sounds a lot like 
what Brad was saying, last week.)

Also, in order to ensure that I was making myself understood, I asked them, 
"Which of the following is the correct source to drive our on-die interconnect 
Touchstone files: an ideal step, or a model of the driver?" They answered, 
unequivocally, "A model of the driver."

Looking forward to hearing everyone's thoughts on this, although I won't be 
able to attend this week.


David Banas
Sr. Member Technical Staff
+1-408-544-7667 - desk

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