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DAC5670: Periodic disturbance at output

YIQI MENG
Prodigy 10 points

Part Number: DAC5670

Hi

We have 2 DAC5670 on our boards with same clock source at 1.2Ghz and interfacing with 2 FPGAs. DAC1 is performing as we expected while DAC2 is not.

We tried a simple ramping function. normal mode; oscillator at 1.2Ghz; .DA DB at 300Mhz DDR. 

DAC1 (correct) gives

while DAC2 output is

Zooming DAC2 OUTPUT, we found this periodic disturbance at around every 500us

Could you give some insight as in what condition this will happen? Thanks 

  • 0
    TI__Genius 14540 points
    Hi,

    If I am interpreting the screen shots correctly, the last screen shot shows the pk-pk voltage at the output of DAC2 collapsing at the disturbance points. This would happen if the output stage is current starved. Could you please do the following:

    1) Capture screenshots of the REFIO & RBIASOUT pins for both DAC1 and DAC2.
    2) Capture screenshots of the power supply rails for both DACs. Are there any differences in power supply sources and filtering.
    3) Provide a schematic (via email if required) of the system including power supply scheme.
    4) Confirm the 500us periodicity of the disturbance. Does the time vary or are disturbances always 500us apart?


    Thanks
    Christian
  • 0 in reply to Christian Yots
    TI__Genius 14540 points
    Hi,

    As I haven't received any feedback on this issue in several weeks, I assume the issue has been solved and will close this thread.

    Thanks
    Christian