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AD7690 PMOD eval software questions


While I am using PulSAR ADC PMODs and picked AD7690. I have the findings and questions listed below.

  1. It limits the maximum sampling frequency to 244 kSPS instead of the full speed 400 kSPS, is this true or just some limitations in my side?
  2. The inputs should do the level shifting from signal source side, not the ADA4841's doing the 2.5V level shifting as shown in its schematic, is this should be ac-coupling or the level shifting must happen in the signal source side.
  3. When I export the data from waveform window, it seems it is 1 sample fewer than the displayed 524288, instead I got just 524287 samples though 524288 lines in CSV file.
  4. The calculation of the input and output signal's amplitude is wrong, it seems to be half of the real value. And I confirmed this from 38.15uV/LSB. Please double check it. The max code is 259775, min code is 2436, thus the voltage range is 38.15uV*(259775-2436) = 9.81748V, but the software shows 4.90833V, which is almost exactly half of the value calculated from datasheet Table 7.

5. I found I cannot do linearity evaluation based on this software. Anything you can help me for the INL, DNL evaluation? TI's EVM can do this and it is very convincing. And if you guys have the plan to implement this function, please let me know when it can be available.

6. If I wanted to do continuous sampling or wanted to get more than 524288 samples each time, anyway I can do it. If there is existed software or firmware can enable me do that, feel free to let me know, please.