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AD6676 linearity - DNL, INL

Question asked by JanBilek on Apr 12, 2017
Latest reply on Apr 14, 2017 by PMH



I'd like to understand how linear the transfer characteristic of the AD6676 actually is. Unfortunately, I can't find any information on this topic neither in the datasheet nor on this forum. Ideally, I'd appreciate to know the DNL, INL numbers which are typically available for pipeline ADCs.


I understand that due to internal DSP functions it is hard to assess linearity on the output data that is already downconverted and decimated. However, I assume this should be doable at least on the core 5bit sigma-delta converter, right?  ...Hence I have done some data acquisition using your AD6676 Evaluation HW (AD6676EVK + supplied Capture card) + SW (=> limitation to 32k samples ) and signal analysis (histograms) in Matlab. I used Direct mode, no decimation. Sinusoidal input from a pure R&S signal generator.  You can see an example screenshot of the output DNL graph in the attachment (Y-axis = DNL [LSB], X-axix = quantization level).


However, I doubt if these results have any value, if it can tell me something about behavior of the ADC.


Do you have any suggestion how to assess linearity behaviour of this ADC? Any hints? Or have YOU already done some measurements that you can share with me???


Looking forward hearing back from you,