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DAC5687EVM: parallel data transfer

yunus emre acar
Prodigy 145 points

Part Number: DAC5687EVM

Hi ,

I'm trying to test the dac5687evm. I need 0-1V output. My data is changing with a 100 MHz frequency.

I'm applying 16 bit digital data to  J14 and 100MHz clock to J4. 

I'm trying to monitor the output from J19 (I'm using a current to voltage converter (an op amp with a 50 ohm feedback resistor) )

The output signal is expected to be a 20 kHz sine wave but I monitored a 60 Hz 1.6Vpp signal (not a sine not a square wave)

How should I configure the DAC5687 EVM ? What I'm doing wrong?

Thanks a lot

  • 0
    TI__Mastermind 20541 points
    Hi Yunus,

    From your description it sounds like you are running the DAC in External clock mode. In external clock mode your clock amplitude should be 1-Vpp 0V offset. In External clock mode CONFIG 1 BIT 5(dual_clk) should be set to 0 and PLLVDD is tied to 0V.

    The following setup will let you generate signal without input data being send into the DAC.

    Open the DAC GUI
    set Dual clk = off
    DAC Serial data = on
    DAC Static data = max value possible
    NCO = on
    Under NCO block
    Fdac (MHz) = 100
    NCO = 10
    click update

    You should see 10 MHz signal on DAC outputs. This will tell you if your DAC is working.

    After words change the gui for following settings
    DAC Serial data = off
    NCO = off

    Now depending on the interpolation selected your data rate going into the DAC has to be adjusted. For example if interpolation is x2 and you are providing 100MHz clock at J4 your data should be 50MSPS and also it is very important you data meets setup and hold time as shown in in figure 43. Also you can use PLLLOCK to drive the input data source that send data into the dac.

    Regards,
    Neeraj Gill
  • 0 in reply to Neeraj Gill
    Prodigy 145 points
    Hi Gill,
    To monitor the output signal on the oscilloscope, I removed R6, R8, R21 and T2 and install R19 (24.9 ohm) and R20 (24.9 ohm). I make R27, R30 and R32 short circuit. (I just use the B port)
    I applied the setup you offered but I just monitor a 2,8V DC signal with 40 mVpp ripples. When I change the setup like
    DAC Serial data = off
    NCO = off
    I monitor a 2,8V DC signal with 160 mVpp ripples.
    when I use a spectrum analyzer I see a 100 MHz signal at the output.