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Measure DNL/INL in ADE-XL

migrg

Hi, I am trying to characterize a DAC design and I need to measure these parameters for my design. The way I'm doing it is by sweeping all the input digital codes in a transient simulation. I can use the INL/DNL functions included in the calculator and this works relatively well:

dnl(VT("/OUT") 5e-09 ?mode "auto" ?crossType "rising" ?delay 0.0 ?method "end" ?units "abs" ?nbsamples nil)

but the problem is that the value at time 0 seems to be always 1LSB. When I do optimization or monte-carlo, I want to look at a single number so I'm trying to measure the min or max value of the DNL/INL (using ymin/ymax) to assess the worst-case. Then this 'wrong' value at 0 makes that very hard. I tried setting up a delay inside these functions but the result was the same. 

Any help would be appreciated!

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  • migrg
    I'll share my workaround: first sample the waveform with the same interval you want to use in the DNL function, but skip the first sample. In my case is every 5ns, and my sampling starts at 5n:

    dnl(sample(VT("/VOUT") 5e-09 5e-06 "linear" 5e-09) 5e-09 ?mode "auto" ?crossType "rising" ?delay 0.0 ?method "end" ?units "abs" ?nbsamples nil)

    this produces the right behavior. Not sure why the DNL function doesn't work directly or what I was missing there.
Reply
  • migrg
    I'll share my workaround: first sample the waveform with the same interval you want to use in the DNL function, but skip the first sample. In my case is every 5ns, and my sampling starts at 5n:

    dnl(sample(VT("/VOUT") 5e-09 5e-06 "linear" 5e-09) 5e-09 ?mode "auto" ?crossType "rising" ?delay 0.0 ?method "end" ?units "abs" ?nbsamples nil)

    this produces the right behavior. Not sure why the DNL function doesn't work directly or what I was missing there.
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