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Cadence SKILL/Ocean loading and saving dc operating point in dc sweep simulation

MatthewT

Hi,

I looked into web and cadence manuals, but I cannot find the answer to my question. I think I saw it some time ago on our forum here, but I cannot find it right now.

I'm running dc simulation:

analysis('dc ?dev "/voltage_dc_source"  ?param "dc"  ?start "value_low" ?stop "value_high"  ?step "1m" )
envOption(
          'analysisOrder  list("dc")
); envOption
run()


I would like to have faster convergence. I found following commands:
- write
- writefinal
- readns

I can run .tran simulation with "?writefinal" attribute pointing to the file where .op of the circuit will be saved and then load it for dc simulation:

analysis('tran ?stop "500n" ?writefinal "tran.fc")
envOption(
    'analysisOrder  list("tran")
); envOption
run()

(...)

analysis('dc ?dev "/voltage_dc_source"  ?param "dc"  ?start "value_low" ?stop "value_high"  ?step "1m" ?readns "tran.fc" )
envOption(
    'analysisOrder  list("dc")
); envOption
run()    


however in such a case, every dc simulation uses the same input tran.fc file. The question is, is it possible to:
1. run 1st dc sweep
2. save calculated dc operating point
3. start 2nd sweep
4. load dc operating point from the 1st sweep
5. run 2nd sweep
6. save dc operating point of 2nd sweep
7. and so on ...

?

Parents

  • The difference is not only in the first dc step calculations. It is clearly visible that the simulation in case 2 is faster than in case 1 for next steps. Especially, when the simulator meets convergence problems and switches homotopy methods. It does not look like the next dc step uses an operating point calculated in a previous dc step, what most probably would be ideal. If it was so, there would be no difference between cases 1 and 2 except the first dc step operating point calculations.

Reply

  • The difference is not only in the first dc step calculations. It is clearly visible that the simulation in case 2 is faster than in case 1 for next steps. Especially, when the simulator meets convergence problems and switches homotopy methods. It does not look like the next dc step uses an operating point calculated in a previous dc step, what most probably would be ideal. If it was so, there would be no difference between cases 1 and 2 except the first dc step operating point calculations.

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