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DAC38J84: NCO Reset

Pavan
Intellectual 670 points
Part Number: DAC38J84

Hi 

I have tried NCO Reset through SYSREF .

I have generated 100 MHz NCO Signal and doing the Reset on Sysref Pulse.

I have observed that there is 180 degrees phase change on doing the NCO Reset.

Why particularly there is 180 degrees phase change. Any Specific Reason ?? 

Ideally after reset, it must start with 0 degrees phase, but why I am getting 180 degrees ?? I have attached the Picture

In my final application I need to use NCO of 600 MHz . So it is difficult to observe it on Oscilloscope.

So How to make sure that NCO reset is done at 600MHz (Mixed with Singletone and LFM Data) ???

  • 0
    TI__Guru 66004 points

    Pavan,

    by default, the NCO resets to 0 degree. You may have phase inversion at the DAC output due to the balun routing. This may be the case if you are using the EVM.

    You will need to use a higher speed scope to monitor 600MHz (usually 3x the frequency or more if you are testing square waveform).

    -Kang