[Magic-dev] Extracted capacitance values in Magic 7.2 and 7.3

[Graham Petley]

Hi,
   I'm upgrading from magic 7.2.70 to 7.3.117. I've noticed differences in the
values of extracted capacitors using exttospice in the two programs, as shown
below:

C6  a    vdd  0.023f *0.025
C0  a    vss  0.031f *0.034
C19 a    vss  0.029f *0.027
C2  a    b    0.177f *0.192
C9  n1   a    0.225f *0.273
C12 a    z    0.020f *0.020

The values after the * are 7.2 and before are 7.3. I've seen from the revision
log that many changes have occured with the extract. Would this explain the
discrepancies, or should the extracted cap values be unchanged?

   I think that in 7.2 the extract didn't take account of any layer over or
undersizing as defined in the cifoutput section. If so the 7.2 values above are
wrong by a small amount. I don't know whether 7.3 extract fixes this.

   If the extracted caps should be the same, I'll create some test circuits to
try to find the origin of the discrepancies.

Best regards, Graham Petley