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CAPTABLE file

RahulRc

Hi all,

 i am going through the Captable file, but unable to understand the format and info given in the file.

 can anyone explain me the same.

 Thanks in advance.

  • Captable file contains resistance and capacitance values which are used to model the interconnect parasitics of a design. Captable files usually contains resistance value and capacitance values. The capacitance values for a range of width and spacing of each metal used in the corresponding technology are defined.     an example is as shown below  for  metal 1(M1) :

    width(um)  space(um)   Ctot(Ff/um)  Cc(Ff/um)    Carea(Ff/um) Cfrg(Ff/um)
    0.500             0.360               0.2606       0.0912       0.0459       0.0156
    0.500             0.450               0.2309       0.0730       0.0459       0.0190
    0.500             1.400               0.1653       0.0153       0.0459       0.0442
    0.500             2.350               0.1618       0.0041       0.0459       0.0537
    0.500             3.300               0.1615       0.0011       0.0459       0.0566
    0.500             4.250               0.1615       0.0003       0.0459       0.0574    

    the total cpacitance, coupling capacitance,area capacitace, fringe capacitance are defined. This information is used while extracting the nets.

  •  Hi Gops,

     Thanks,

    but there is a table called extended cap table after a captable.

    what is a significance of  extended cap table?

    Thanks in advance.

  •  I believe the extended cap table is created when you pass your tech LEF to generateCapTbl. It covers the cases of NONDEFAULT rules. If you have any NONDEFAULT rules in your tech lef, you should include it when generating the cap table.

  • Hi RahulRc,

    The basic purpose of extended cap table is to produce accurate R and C values in Extraction.

    As you know the basic info of capacitance for each metal layer has given with some limited spacing and width values in the cap table.If the Extraction engine is not able to see a value for capacitance for a particular net while extracting (means if the capacitance value is not within the range of given values of spacings and widths defined in cap table),it calculates from the extended cap table.

    Please do let me know whether you are clarified with this.

     

     

    Best Regards,

    mmkrcool

     

  • in reply to gops

    Hello, I have a question about the captable fie. I want to know the table show  capaticance is the final capacitance value,or is the capacitance for unit width. That is to say, for the first line,when width=0.500u, space=0.360u, the final capacitance=Ctot=0.2606Ff. Or the final capacitance = 0.500 * Ctot=0.500 * 0.2606Ff. Can anyone tell me? Thanks a lot !

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