How to determine capacitance of input pin with spectreS

Hello,

Can anyone give me a hint how I determine the capacitance of an input
pin of a standard cell (extracted netlist) with spectreS?

Thanks in advance for any help.

Thomas

 

watch the net-list and add all capacitances connected to that node.

 

You mean I have to do it by hand??? Or is there a function in spectreS
(OCEAN) which does the trick automatically? I've heard that a typical
SPICE simulator is able to calculate the capacitance of every node of a
given netlist. So I strongly presume this is also possible with spectreS...

-Thomas

 

don't know any special function. However, if you want to compute
the parasitic capacitance at the input of a cell, you can do the following.

open layout & schematic views
run extraction on layout, then LVS
LVS must be successful
then, on LVS window select "parasitic probe", push "whole net" and select a
net in
the schematic. This will add up all parasistics and display the result.
However, it non-parasitic capacitors won't be taken into account.
hope this helps,
s.badel

 

Thomas,

I think you are looking for the "captab" function of spectre. Here is an
example how to include it in a netlist for a DC run (it is not in the gui
yet, so you might load it over an include file ):

dcOp dc write="spectre.dc" maxiters=150 maxsteps=10000 annotate=status \
infoname=capinfo2
capinfo2 info what=captab where=file file="capnodesdc"
dcOpInfo info what=oppoint where=rawfile

Regards,
Marc

Regards,
Marc

 

Thanks a lot, that worked!

But I had to do it slightly different: open layout - run extraction -
open extracted view - open LVS window - select "parasitic probe" - push
"whole net" and select a net in the extracted layout
No schematic view or LVS-run was needed...


-Thomas

 

The simples way is to run the simulation driving the input from a
voltage source and integrate the current on the input pin.

Two notes:
- the precision of the simulation is very important;
- the input cell capacitance may depend on the state of the other input
pins (miller effect).

Robert

 

Thanks for your help Marc!

Actually I'm running the simulation of my standard cells with OCEAN
using the simulator spectreS.

Until now I don't mess around with the simulation netlists. I get them
by creating a simulation schematic for a cell and starting the "Analog
Environment". Then I create a raw and a final netlist of the whole
simulation circuit (using the extracted netlist of the simulated
standard cell). These netlists are then used by a OCEAN skript to
perform the simulation.

My question is: Is it possible to use OCEAN to tell the simulator
__spectreS__ to compute the capacitance of an input pin of the simulated
standard cell?


-Thomas

 

Hi Thomas,

as far as I know captab did not exists in spectreS.
The easiest would be what Robert suggestet. Let OCEAN do a simulation of a
voltage source on your pin and do the postprocessing (integration) inside
the same OCEAN script.


Marc