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MMSIM 6.2 - Spectre question

yoyega

Hi,
I am using MMSIM 6.2 to run some Spectre simulations and I am having some unexpected problems with the results. I am simulating files netlistTRAN022.1x1.saveall.PHC.scs and  netlistTRAN022.1x1.saveselected.PHC.scs. The only difference between these files is the following options statement:

(in netlistTRAN022.1x1.saveall.PHC.scs)
saveOptions options save=all pwr=all currents=all useprobes=yes

(in netlistTRAN022.1x1.saveselected.PHC.scs)
saveOptions options save=selected currents=selected useprobes=yes

but simulation results for the saved signals are completely different depending on the scs file I run. As far as I understand, the above options statements should not change the results of a simulation, only the signals to be saved to HHDD, am I right?

Do you know which could be the problem?

 Thanks,

Pedro

Parents

  • If you take a look at the spectre output log file, in particular in the circuit inventory, you'll see a difference (I suspect) in the number of iprobes appearing in the circuit. This alters the size of the matrix being solved, and consequently it can affect the convergence. Normally the results may be very slightly different, but if bigger, it is normally indicative of the fact that you may have multiple stable operating points in your circuit (rather like hysterisis in a comparator, but it could be other things).

    In the Simulation->Options->Analog you can enter "subcktiprobes=no" in the additional parameters field at the bottom of the form. If you do this it uses an alternative method for measuring currents (although I think if you set useprobes=yes it may stop this and still use iprobes). Is there a particular reason why you're using useprobes=yes? (it's normally only needed for currents in AC-type analyses).

    Regards,

    Andrew.

Reply

  • If you take a look at the spectre output log file, in particular in the circuit inventory, you'll see a difference (I suspect) in the number of iprobes appearing in the circuit. This alters the size of the matrix being solved, and consequently it can affect the convergence. Normally the results may be very slightly different, but if bigger, it is normally indicative of the fact that you may have multiple stable operating points in your circuit (rather like hysterisis in a comparator, but it could be other things).

    In the Simulation->Options->Analog you can enter "subcktiprobes=no" in the additional parameters field at the bottom of the form. If you do this it uses an alternative method for measuring currents (although I think if you set useprobes=yes it may stop this and still use iprobes). Is there a particular reason why you're using useprobes=yes? (it's normally only needed for currents in AC-type analyses).

    Regards,

    Andrew.

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