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DAC5675A Output Bandwidth

Troy Baldonado
Prodigy 20 points
Other Parts Discussed in Thread: DAC5675A

What is the Output (or Analog) Bandwidth of the DAC5675A?

  • 0
    TI__Mastermind 20541 points
    Hi Troy,

    I am looking into this question. I will get back to you after talking to the designer.

    Regards,
    Neeraj Gill
  • 0 in reply to Neeraj Gill
    TI__Mastermind 20541 points

    Hi Troy,

    Based on the output capacitance (5pF) mentioned in the datasheet and assuming a doubly terminated 50ohm || 50ohm = 25 ohm output resistance would give us f(-3dB) =~ 1/(2*pi*25*5e-12)=~1.25GHz of bandwidth. But remember the output signal will be mostly shaped by sinc function response which usually starts to role-off after Fs/2.

    Regards,

    Neeraj Gill

  • 0 in reply to Neeraj Gill
    Prodigy 20 points

    Hi Neeraj,

    If the bandwidth is 1.25GHz and understanding that we are bound by the sinc function response that typically starts to roll off at Fs/2, what is the expected SFDR from 100MHz to 1.25GHz? We may still be able to use this DAC in our proposed design change for our production units but need to know the expected roll-off. Does TI have any data on the response of the DAC that we can refer?

  • 0 in reply to Troy Baldonado
    TI__Mastermind 20541 points

    Hi Troy,

     

    This DAC is designed for 1st Nyquist operations with max sample rate of 400MSPS. 1st Nyquist would be at 200MHz. As I mentioned before the output signal will be shaped by sinc function.

     

     The figure above shows the general amplitude we would expect to see based on the output frequency. As you can see depending on where the output signal is the amplitude can vary 0 to -50 dB.

     

    Can you please specify output frequency values where you want the SNR to be measured? Also want to mention in second and third Nyquist zone because of the shape of sinc function you cannot use wide band signals.  

     

    Regards,

    Neeraj Gill