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Updated Spectre Transient Noise Problem

Stepan

Hi,


Recently, our institute updated the Spectre simulator version from 7.1.1.187.isr11 64bit to 11.1.0.509.isr14 64bit and I found out that the transient noise simulation started to yield different results for the same netlist and parameters that I used with the Spectre previous version:

    start = 0 s
    outputstart = 4.82154 ms
    stop = 4.82154 ms
    step = 4.82154 us
    maxstep = 36.7647 ns
    ic = all
    useprevic = no
    skipdc = no
    reltol = 100e-06
    abstol(V) = 1 uV
    abstol(I) = 1 pA
    temp = 20 C
    tnom = 27 C
    tempeffects = all
    errpreset = conservative
    method = gear2only
    lteratio = 10
    relref = alllocal
    cmin = 1 fF
    gmin = 1 pS
    noisefmax = 136 MHz
    noisefmin = 207.52 Hz


My netlist is a post-layout extraction of a high-resolution switched-capacitor delta-sigma modulator. From spectre version 7 to version 11, I loose one bit of resolution (a SNDR reduction from 108dB to 102dB). Nevertheless, disabling the noise option, I obtain similar results for both versions (110dB SNDR).

Were there any transient noise simulation issues reported in the versions previous to 11 that made me believe in more ideal behavior of the modulator?

Thanks,

Stepan.

  • This is a pretty hard question to answer. Asking about changes between a release that came out in 2008 to one that came out in 2011 (so even your new release is 3-4 years old) when there were three major releases between the two (including MMSIM11.1) would be pretty difficult to pinpoint.

    I'm sure there were transient noise issues reported and fixed between those two releases, and it's also quite likely that there have been other fixes since then to the current date!

    So who knows?

    Regards,

    Andrew.

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