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DAC39RF10: NCO Change

Kazuki Itoh
Genius 10165 points
Part Number: DAC39RF10

Tool/software:

Hi team,

1. In Phase-continuous NCO Update Mode, is it possible to change NCO while having RF output?
Or should it better to stop the RF power and then change (hop) the NCO?
2. How much interval should the device have to make the next NCO change after the NCO change?

Best regards,
Kazuki Itoh

  • +1
    TI__Mastermind 22660 points

    Hi Kazuki,

    1. It is possible (and most common) to change the NCO while the output is enabled. The only reason you would really disable the DAC output, then update NCO settings, then re-enable the DAC output is if you need to stop the DAC output in order to adjust some other components in the system. As an example, consider a programmable attenuator at the final output stage of some system. If the DAC is at NCO freq #1 and the DAC output level is at 0dBm, when you change to NCO freq #2, the analog output circuit supporting the DAC may not be linear so the output could be something like a +1dBm signal, so the system may need to compensate for this by adjusting a downstream attenuator by 1dB so the output RF power stays the same to prevent damaging some other downstream amplifier or device. Most systems won't have or need anything like this so NCO updates without disabling the DAC output is the standard behavior.

    2. The NCO can be updated as fast as the words can be programmed. There is no minimum time that the DAC has to stay at an NCO frequency. 

    Thanks, Chase