Any Suggestions on ring oscillator verification

Discussion in 'Cadence' started by Sam, Jun 27, 2005.

  1. Sam

    Sam Guest

    Hello all,

    I am a little lost. I received a spectre model of the 0.35um Mixed
    Mode proces from Mosis (really TSMC's 3.3V/5V Mixed Signal process) and
    was trying to verify the ring oscillator values listed in spice model
    document. I thought a quick verification of the ring oscillator table
    would be a good double check of the schematic entry to simulation flow.
    Unfortunately, the values I get and the values listed is about 40% off!
    I am a little puzzled and perhaps it is my understanding of
    AD,AS,PD,PS and the relavance to hdif and ld. Or maybe something more

    I am using ic5.0.33 spectre simulator and have connected n(odd)
    inverter strings that match the description (including w and l for nmos
    and pmos devices) in the document. Supply was set to 3.3V, temp set to
    25 degrees C, initial conditioned a single inverter input/output node
    to 0, and ran a transient simulation for 40ns. I have tried both
    specifing AD, AS, PD and PS and and not specifying them and got
    similiar errors.
    given, then it defaults to the hdif parameter, if hdif is not specified
    then it goes to the ld parameter, and finally gives 0 if no ld
    parameter is defined. Is my understanding correct? Incidentally, the
    document specifies that hdif, xw and xl was modified to get the results
    listed, which I also did in the model file. I am assuuming the hdif
    comment indicates that they did not specify AD,AS,PD,AS.

    Because the only item provided was the model file, I used the analogLib
    nmos4 and pmos4 symbols and just changed the w,l, and model name to

    Any help would be greatly appreciated and thank you for time in reading

    Sam, Jun 27, 2005
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