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https://designers-guide.org/forum/YaBB.pl Measurements >> Other Measurements >> Measure INL/DNL for 16b Sigma-Delta ADC https://designers-guide.org/forum/YaBB.pl?num=1252068987 Message started by ywguo on Sep 4th, 2009, 5:56am |
Title: Measure INL/DNL for 16b Sigma-Delta ADC Post by ywguo on Sep 4th, 2009, 5:56am Hi Guys, It seems to be very difficult to measure INL/DNL for high resolution ADC, saying a 16b ΣΔADC. It needs about 40 milliion samples if keeping 95% confidence level for a 16 b ADC. I have a logic analyzer with memory depth of 2M at hand. So I think perhaps that another testing method is prefered. Even I worry about the signal source. What's your experience in measuring INL/DNL for high resolution ADC? Any comments are appreciated. Best Regards, Yawei |
Title: Re: Measure INL/DNL for 16b Sigma-Delta ADC Post by vivkr on Sep 11th, 2009, 1:19am Hi Yawei, Depending on the speed and your signal generator, you might want to consider using a ramp signal instead of a sinewave. The number of samples needed drops dramatically since the distribution of the input codes is now uniform instead of bathtub. I remember using such a method for a 14b ADC. Already at 14b level, the number of samples needed was impractically high with a sinewave. Naturally, there are several disadvantages, the most important being: (a) difficulty in generating pure ramps. (b) cannot use a filter to purify the signal. What you can do in addition is to use a collection of tests to deduce the INL/DNL. In addition to the ramp test, I would recommend the following: 1. A fullpower sinewave test and FFT with coherent sampling (prime number of input cycles) in order to catch as many codes as possible. 2. Running several "localized" INL/DNL histogram tests with sinewave signals approx. FS/32 centered around various critical points in your code range. So for instance, if you had a traditional SAR ADC, you would run a histogram test around 0, +/- FS/2, etc. 3. Transferring data offline to a PC for INL/DNL analysis instead of using a logic analyzer. This may not work if you want to do rapid tests for INL/DNL (I doubt if anyone does that in production for 16b ADCs). Regards, Vivek |
Title: Re: Measure INL/DNL for 16b Sigma-Delta ADC Post by loose-electron on Jan 8th, 2010, 1:59pm I wopuld approach it a little differently - first, INL-DNL are static tests - automate that with a PC and do it --- DC in --- code out --- type of thinking. From there, I would runs some linearity tests in a dynamic fasion. |
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