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DAC38RF84: How to switch two NCO?

ArTzy
Genius 17365 points
Part Number: DAC38RF84

Hi Experts,

Good day. I have this query from client:

It shows that two NCO of DAC38RF84 can switch to change one frequency to another frequency quickly. Page #35 of DAC38RF84 D/S, it showed the outputs of NCO1 and NCO2 were summed together.

Does it mean both frequencies are generated together? If we want only one frequency every time, but require to switch frequency quickly from NCO1 to NCO2. How can we do this?

Thank you for your support.

Regards,
Archie A.

  • 0
    TI__Guru* 91947 points

    Archie,

    The device can be setup to have either 1 or 2 NCO's for each channel. Using the output summer (address 0x19 in pages 1 and 2), you can send any or all NCO data paths to any output. For example, if you want to switch between two frequencies as quickly as possible for CHA, you would program both NCO's (2 IQ mode, figure 25 of data sheet) to the desired frequency setting, then set the output summer to only send one of these output paths to the DAC A output. With a single register write, you could send the other NCO path to CHA instead. The SPI clock frequency will determine how fast this will occur. 

    Regards,

    Jim