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DAC39J82EVM: Confirm if can generate a sawtooth 2 to 5 ns wide and 10us rep rate

Jonathan Geronga
Expert 7930 points
Part Number: DAC39J82EVM
Other Parts Discussed in Thread: DAC38RF82

Hi Team,

I would like to confirm if DAC39J82EVM can generate a sawtooth 2 to 5 ns wide and 10us rep rate as part of the customer requirement.
Also, can this DAC work with or without the NCO?

Please let me know if there are better products for this customer requirement or if you have other questions.

Thanks,

Jonathan

  • 0
    TI__Guru* 91947 points

    Jonathan,

    The DAC can work with or without the NCO. I am looking into your other question.

    Regards,

    Jim

  • 0 in reply to jim s
    TI__Guru* 91947 points

    Jonathan,

    You can bypass the NCO and then would have 2 independent channels. The maximum input rate is 1.4GSPS, which would have a sample time of 0.7ns. For a 2ns wide sawtooth, this would only provide 3 sample points. In bypass mode (no interpolation), the output would look like stairs with 3 steps. You could interpolate by 2x, which would double the # of steps to 6 with a time of .35ns each, but this would introduce some ripple in the time domain.

     

    The DAC38RF82 would be a better fit. It has a 8 bit input mode at 9GSPS with .11ns sample time – that would provide > 20 samples during the 2ns sawtooth rise time. Either the natural bandwidth limitation (~ 4GHz) or an additional filter roll off could be used to smooth out the stair steps.

    Regards,

    Jim