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AD9764 output

Hi

I have designed a DAQ borad including AD9764, AD6644 and it communicates with Xilinx Spartan 3AN FPGA through FX2 expansion connector.

As indicated in the attachments we can see the input&output connections and the clock signal (which is RC filtered version of Clockin at 16MHz coming from the FPGA) . I am wondering why i am getting the same voltages at the IOUTA and OUTB nodes at the AD9764 output (simply 0 or 20mV at the output of AD9631 opamp ) although I apply the code "00000001111111" from the FPGA. I checked the DAC inputs and see that they are as the FPGA output.  Is it about the AD9764 or the AD9631 opamp or the noise level?

I will appreciate any help .

Thank you very much

HIDIR

attachments.zip
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  • Hi

    I have connected the suggested components R20, R38,C12, C13.

    Now I observe (with the DC coupled channel of the oscilloscope)

    V_IOUTA=900mV and V_IOUTB=12mV with 120 and 4 mVpk-pk .The voltage at the OPMAP inputs are 3 and 7 mV respectively. The opamp output is -845 mV .

    The 3.3VD supply sources 29mA, 74 mA and 112mA for the DAC codewords of      "00000000000000",   "00000001111111" and "11111111111111" respectively.

    I could not see difference in the output .

    Any help about how to carry the DAC output test steps  or the problem I face ..

    Thank you

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  • Hi

    I have connected the suggested components R20, R38,C12, C13.

    Now I observe (with the DC coupled channel of the oscilloscope)

    V_IOUTA=900mV and V_IOUTB=12mV with 120 and 4 mVpk-pk .The voltage at the OPMAP inputs are 3 and 7 mV respectively. The opamp output is -845 mV .

    The 3.3VD supply sources 29mA, 74 mA and 112mA for the DAC codewords of      "00000000000000",   "00000001111111" and "11111111111111" respectively.

    I could not see difference in the output .

    Any help about how to carry the DAC output test steps  or the problem I face ..

    Thank you

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