AD9629 Read

Hi,

I am new to reading ADC. I want to use AD9629 in my design. And i want to read this with FPGA. How can i handle it? Where should i start when writing the VHDL code? What are the things i should be aware of?

Best regards.

  • Hi Harun,

    Is your CSB pin connected to DRVDD to put the AD9629 in "pin mode" (non-SPI mode)?

    Thank you.

    Doug

  • Yes, my CSB pin connected to DRVDD.

    Thank you.

  • Hi Doug,

    I am sending some values that i saved.

    Vin+ - Vin-              ADC Output

    -1V                              800

    -0.28V                         DA9

    0V                               807

    0.32V                          AB4

    0.68V                          D75

    1V                               FFF

    According to my results, the ADC does not work properly when the Vin+ - Vin- value goes to negative. 

    And also my DCO signal is not exactly a square wave, it is a sinusoidal wave. Could this be the source of the problem?

    Thanks.

  • Hi Harun,

    I agree that your output codes for positive differential input voltages look good.

    Your output data for negative input voltages seems to have the same slope (ADC gain) as the output codes for positive values. Also, the data point you provided earlier with 0.46V - 1.34V = -0.88V falls almost on the same line. It is like you are adding an offset to your output codes when the MSB = 0.

    Could you double check your FPGA design? Is it possible you are adding an unintentional offset of 2^11 to the codes for when the MSB = 0? When I subtract 2^11 from your output values when MSB = 0 (for negative differential analog input voltage), your output codes vs. input voltage all fall on a straight line.

    Thank you.

    Doug

  • Hi Doug,

    I checked my FPGA code and there is no an unintentional offset. And also i checked the output signals directly from the ADC parallel channels(no processing). The results is still the same.

    Thank you.

    Harun