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Changing fine mixer settings on DAC34SH84EVM

Alexander Sotnikov
Prodigy 10 points
Other Parts Discussed in Thread: DAC34SH84, DAC34H84, DAC3484

Hi i'm trying to set up fine frequency mixing using the internal NCO of DAC34SH84 on DAC34SH84EVB/. The part is configured for operation with 375 MHz external reference/data clock frequency and 4x interpolation. When i enable the coarse mixer everything works as intended, but when i put it in bypass and leave the Mixer Enable check-box active i get multiple tones at different positions in Nyquist band instead of just one. The positions of tones don't change when i try changing NCO settings. When i turn on Mixer enable, choose , for example, fs/4 coarse mixer and try changing NCO settings frequency of the signal at the DAC output doesn't change as well. Could you help me to find where the problem is, please!

Also i noticed that for my choice of DAC the names of second and third columns in CDCE62005E Control window are swapped for some reason.

The screenshots of DAC EVM Software Control windows are attached below:

  • 0
    TI__Guru* 78164 points

    Alexander,

    The NCO spectrum is most likely due to the NCO not being synchronized. You can try using the SIF_SYNC button to synchronize the NCO. See attached for detail.

    The DAC34H84/SH84 EVM has the OSTR and DACCLK swapped when compared to the DAC3484/82EVM. This is done to optimize the EVM layout to avoid clock crossing. On the top of the GUI in the black region, you can use the pull-down menu to change from "DAC3484 EVM Software Control" to "DAC34H84/SH84 EVM Software Control".

    -KH

    DAC3484 NCO.ppt