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VPULSE source exhibits different behaviour for 'static' and 'periodic-autonomous' circuits!

Wavefunction
In need of a step source for my .tran simulation in Cadence 5.10.41 and Spectre 7.1.1 environment, I chose a vpulse source from analogLib. But it refuses to toggle and stays put at the same intial voltage level of val0 in an autonomous circuit, whereas it works as expected when I use it in static circuits without a periodic operating point. I presume, the circuit type should not have a say in the behaviour of the voltage source, or should it ? Here's the part of the generated netlist describing this source: ----------------------------------------------------- V1 (net020 0) vsource type=pulse edgetype=linear val0=700.0m val1=1.8 \ period=250n delay=50n rise=1p fall=1p ----------------------------------------------------- I cross-verified that the $CDS_Netlist_Mode is indeed 'Analog' and I ran the .tran for 1.5us which is obviously larger than the period of the vpulse. Any inputs on this are utmost welcome!! Thanks a lot.
  • Andrew Beckett

    The fundamental problem is that you've not specified the width parameter - and hence it doesn't know the width of the pulse. However, I don't see what you see - I see that it varies as attached. This happens whether I use an autonomous circuit or not. I have the same statement as you (assuming that the line breaks after the backslash).

    Regards,

    Andrew.

     

  • Andrew Beckett

    Forgot to mention, I was using MMSIM72 (7.2.0.400.isr14). What version were you using?

    Regards,

    Andrew.

  • Wavefunction

    Hi Andrew, 

    Thank you for your feedback!

    It doesn't work even if I specify a width=125n. Yes, that statement including the backslash is directly from the netlist.

    Besides, I'm using MMSIM 7.1.1.187.isr11 and in case you needed it, the circuit inventory is as follows:

    --------------------------------------

    Circuit inventory:
                  nodes 183
               bsim3v3 444  
              capacitor 22   
                resistor 2    
               vsource 2

    ---------------------------------------- 

  • Andrew Beckett

    I tried MMSIM71 ISR27 and MMSIM 7.1.1.071 (the update release slightly before the ISR you're using). I can't reproduce it.

    Are you sure this is  happening? Your graph actually appears to be for a different node than the one you show in your netlist excerpt.

    Perhaps you can try in a later hotfix in case it's a bug that has been fixed (although it seems unlikely to me, as I doubt this has been touched in years). And if you still see the problem, please contact Cadence Customer Support at http://support.cadence.com so that it can be investigated with your data (or at least being able to observe it somehow).

    Best Regards,

    Andrew.

  • Wavefunction

    I surely comprehend your concern. The graph and the netlist shown are from different hierarchy levels and hence the discrepancy in the names.

    The issue persists when I try with vsource and vpwl as well. Anyway, I shall re-check it with other users and proceed accordingly.

    Many thanks once again for your precious time!

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