• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 46 subscribers
  • Views 284 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TSW1400 + DAC34SH84EVM

Ryan Clement
Prodigy 60 points


Hi

I am having trouble getting a clean signal out of the DAC.  Are there any tricks I need to know about? I have tried multiple sampling rates from 40Msps through to 1.5Gsps with a simple sine wave from the generator in HSDCPro (5 to 25MHz) and the wave generally is very distorted and I can't see a clear step size on CRO (Below is a quick snap shot.  The pink trace is SYNC3 on TSW1400. I believe that should be 1/16 of the sampling rate and it doesn't seem to translate to what I set the DAC to.  I am assuming I should be able to get a fairly accurate sine wave or a square wave out without much effort.  At present my arduino can produce a cleaner wave albeit at 600Hz (12bit DAC),  I have tried 3 different clk sources and it does change the output slightly but none dramatically improve the signal.

Any ideas or thoughts?

Thanks

Ryan

  • 0
    TI__Genius 12965 points

    Ryan,

    The output looks like a sampled output from a DAC.  The DAC EVM typically does not have any filtering and since it has a very wide BW output you will see the entire output of the DAC including the steps of the sample and hold at the output.  If the output were BW limited you would actually attenuate the images of the DAC+S/H and you would see the fundamental sinewave (refer to the SINX/X function time domain vs frequency domain).  From the plot I would think that the DAC is generating a sinewave that is 1/5 of Fdac (output clock rate, not data rate) - 5 samples per cycle.  Considering that there is a min of 2x interpolation, that appears to be quite a high output frequency relative to the DAC output sample rate.  If you have a much lower Fin/Fs then you should see more steps per cycle.

    Are you using the Coarse MIxer or Fine mixer to increase your input signal to a much higher output signal frequency? Can you tell us your input signal frequency, data rate, DAC clock rate and interpolation setting?

    Ken.