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AD9911 DDS frequency synthesizer

Discussion in 'Electronic Design' started by PC, Feb 12, 2009.

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  1. PC

    PC Guest

    Hi All,

    I have been struggling with the Analog Devices chip AD9911 for over a
    week and still no luck.
    The SPI Clk and Data are perfect, all the analog and digital voltages
    are set as specified in the data sheet. Here are some of my register

    CSR - 0x"22"
    FR1 - 0x"1800"
    FR2 - 0x"0000"
    CFR - 0x"000382"
    CTW0 - 0x"9810624D"
    CPOW0 - 0x"0000"

    My target is to generate an ouput frequency of 74.25Mhz with a 25 Mhz
    system clock. Am I overlooking something obvious, have you faced
    similar issues with this chip. Any help in resolving the problem are

  2. Have not used that particular chip, but I suspect something to do with
    the SPI-- data/clock phase-- there are 4 possibilities, number of
    bits, total number of clocks, or format (MSB first is default, right?)

    Best regards,
    Spehro Pefhany
  3. Guest

    What problem? You didn't mention any details. Wrong frequency?
    Amplitude? Shape? No output at all? Chip overheating? What?
  4. PC

    PC Guest

    I Don't get any output at all, although I get a sync_clk output ( 25 /
    4) . The chip is configured in the single bit 3 wire mode, the SPI
    read is also unsucessful. The data sheet doesn't say much about SPI
    programming though.
  5. Guest

    It's a current-mode DAC. You do have a current to voltage converter at
    the output?
  6. Guest

    if spi reads don't work, there's a very good chance spi writes don't
    work either
    so chase that first

  7. Any test outputs ? How about testpattern.
    Incremental approaches ?

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