Assura Extraction

  • Thread starter sridhartv25@gmail.com
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sridhartv25@gmail.com

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Hello all,

I am unable to findout the values of parasitic resistances after
running the Assura RC extraction. I am getting the values of
parasitic capacitances but for the parasitic resistance the output
form is giving the result as NA. So please can someone suggest me the
procedure of finding the parastic resistances.
Cheers,
Sridhar.
 
sridhartv25@gmail.com wrote, on 01/29/09 05:42:
Hello all,

I am unable to findout the values of parasitic resistances after
running the Assura RC extraction. I am getting the values of
parasitic capacitances but for the parasitic resistance the output
form is giving the result as NA. So please can someone suggest me the
procedure of finding the parastic resistances.
Cheers,
Sridhar.
Click to expand...
It would help to most people if you gave more detail of precisely what you were
looking at. I'm assuming you're using the parasitic probing? Or the Show Parasitics?

Anyway, if you want to show the lumped R parasitics, you need to have done a DC
simulation of the circuit - this is the method it uses to lump the R.

If you want to just simulate with the extracted view, then nothing special is
needed - the netlist will contain all the R and C devices with the values netlisted.

Regards,

Andrew.
 
Hello Andrew,

Thanks for your reply,

It's not in the simulation Andrew.

After the layout is completed I had extracted the layout from Assura -
Run RCX....
And then in the extracted view window , I had used the option Tools -
Click to expand...
Parasitics
and then in the Parasitics menu Parasitics -> Report Parasitics -> All
nets.
Then a form is displayed showing the parasitics of all the nets. In
this form I could see the value of parasitic capacitance. But for
resistance it's showing as NA.
I had run RC extraction and also I could see parasitic resistors
symbols in the extarcted view
but I could not get the values in the Report parasitics form.
Cheers,
Sridhar.
 
By the way I am trying to attach the form to be more clear but I could
not see any attach option in this forum.
How could I do this.
 
sridhartv25@gmail.com wrote, on 01/30/09 04:53:
Hello Andrew,

Thanks for your reply,

It's not in the simulation Andrew.

After the layout is completed I had extracted the layout from Assura -
Run RCX....
And then in the extracted view window , I had used the option Tools -
Parasitics
and then in the Parasitics menu Parasitics -> Report Parasitics -> All
nets.
Then a form is displayed showing the parasitics of all the nets. In
this form I could see the value of parasitic capacitance. But for
resistance it's showing as NA.
I had run RC extraction and also I could see parasitic resistors
symbols in the extarcted view
but I could not get the values in the Report parasitics form.
Cheers,
Sridhar.
Click to expand...
Sridhar,

As I said in my previous post, you need to do a DC simulation. Create a
testbench with an instantiation of your block that you have the extracted view
for, connect up all the supplies, and do a DC analysis in spectre. You may want
to use a config view to pick the extracted view for the block...

Then descend down into the extracted view (from the testbench) and do
Tools->Parasitics. In the Parasitics->Setup form you'll see that it's referring
to some simulation results.

Then you can do the Report Parasitics->All Nets and it should show resistances
for each net.

Essentially the DC simulation is needed for the method used to compute the
lumped resistances for each net, as I said before.

Best Regards,

Andrew.
 
Andrew thanks for your reply,
Yes , I had run a dc simulation of the ckt, and the results are fine.
But the problem is in the parasitics -> Setup menu still itis not
referring to the spectre , its referring to the schematic itself.
I had tried hard but I couldnot get what's the probllem is.

Cheers,
Sridhar.
 
On Jan 30, 11:57 pm, "sridhart...@gmail.com" <sridhart...@gmail.com>
wrote:
Andrew thanks for your reply,
Yes , I had run a dc simulation of the ckt, and the results are fine.
But the problem is in the parasitics -> Setup menu still itis not
referring to the spectre , its referring to the schematic itself.
I had tried hard but I couldnot get what's the probllem is.

Cheers,
Sridhar.
Click to expand...
Try to check the postlayout simulation netlist, the parasitic
resistance should be shown there. If you check the parasitics view in
Parasitics->Setup, I found it generally wouldn't give you the value of
resistance as well (I think this might be the parasitic resistance
nets are too complicated). If you check the parasitic resistance
between two points, it may give the value.
 
On Jan 30, 6:57 am, "sridhart...@gmail.com" <sridhart...@gmail.com>
wrote:
Andrew thanks for your reply,
Yes , I had run a dc simulation of the ckt, and the results are fine.
But the problem is in the parasitics -> Setup menu still itis not
referring to the spectre , its referring to the schematic itself.
I had tried hard but I couldnot get what's the probllem is.

Cheers,
Sridhar.
Click to expand...
You need to descend into the schematic for which you want to
backannotate parasitics from the testbench and then select the spectre
results from Parasitics->Setup.
 
Thanks Andrew I got it,
Before I was simulating the ckt without creating the config view.
But in the output form of the parasitics I got the values of the
resistances some thing like ~300m , ~20.
I think ~300m indicates 300 milli ohms but what does this symbol ~
refers to .

Cheers,
Sridhar.
 
sridhartv25@gmail.com wrote, on 02/02/09 05:39:
Thanks Andrew I got it,
Before I was simulating the ckt without creating the config view.
But in the output form of the parasitics I got the values of the
resistances some thing like ~300m , ~20.
I think ~300m indicates 300 milli ohms but what does this symbol ~
refers to .

Cheers,
Sridhar.
Click to expand...
It means "approximately".

Andrew.
 
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