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INL simulation issue for temperature sensor

wgtkan

Hello,

I would like to determine the temperature error of my temperature sensor circuit by using a viva function integral non-linearity of a dc temperature simulation. I want to show the output voltage of the sensor against temperature. 

The temperature is swept from -20 to 100C using the DC sweep. And the simulation is working by plotting the output voltage vs temperature. But when I do the INL simulation to determine the temperature error through the viva function, I am getting what seems the temperature error against voltage but not temperature.

Here is what I have in my viva calculator function:

inl(VS("/vot2") 1 ?mode "auto" ?crossType "rising" ?delay 0.0 ?units "abs" ?nbsamples 120)

Instead of getting a plot that looks like this: 

I am getting wrong plot that looks like this:


My cadence virtuoso version is :
Version IC6.1.8-64b.500.9
Spectre spectre191

Thank you so much in advance for your cooperation with this question.

  • in reply to ShawnLogan

    Hello Shawn,

    I did the simulation-based the calculation you provided which goes like this:

    (waveVsWave(?x waveVsWave(?x VS("/vot2") ?y xval(VS("/vot2"))) ?y (waveVsWave(?x VS("/vot2") ?y xval(VS("/vot2"))) - abBestFit(waveVsWave(?x VS("/vot2") ?y xval(VS("/vot2")))))) - (0.5 * (ymax(waveVsWave(?x waveVsWave(?x VS("/vot2") ?y xval(VS("/vot2"))) ?y (waveVsWave(?x VS("/vot2") ?y xval(VS("/vot2"))) - abBestFit(waveVsWave(?x VS("/vot2") ?y xval(VS("/vot2"))))))) + ymin(waveVsWave(?x waveVsWave(?x VS("/vot2") ?y xval(VS("/vot2"))) ?y (waveVsWave(?x VS("/vot2") ?y xval(VS("/vot2"))) - abBestFit(waveVsWave(?x VS("/vot2") ?y xval(VS("/vot2"))))))))))

    And I get the attached plot which is not quite as I expected. 

    Can you let me know if we are missing anything?

    Thanks, Shawn.

  • in reply to wgtkan

    Dear wgtkan,

    [[quote userid="289980" url="~/cadence_technology_forums/f/custom-ic-design/46607/inl-simulation-issue-for-temperature-sensor/1369471"][/quote]

    And I get the attached plot which is not quite as I expected. 

    Can you let me know if we are missing anything?

    Maybe I did not understand what your intentions were? However, to me, the plot appears totally consistent with what I expected. For each of the three cases you have plotted (yellowfins, red, and green), the peak positive and peak negative magnitudes of each respective curve have the same absolute values over the -20C to +100C range. For example, the green peak positive value is about +780 and its peak negative value is about -780 (I'm not sure of the y-axis units...milli LSB?). In my prior post, I included the following "

    Unknown said:
    I think, instead, you might want the plot to have symmetrical maximum and minimum INL values for each curve in order that you might easily compare the maximum INL value each case provides.

    It appears to me this is exactly what the curve fits provide. Let me know if I misunderstood your actual intent.

    Shawn

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