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DAC37J82: DAC37J82 NCO and Mixer Configuration

Thang pham
Prodigy 20 points
Part Number: DAC37J82

What are the proper steps to configure the NCOs and the mixers in the DAC37J82? 

How do the 3 NCO freq control words are being loaded into the NCO block?  Is it by writing the last register (upper freq word) to trigger an autosync to load the entire field (3 words) into the NCO block? 

Does the NCO accumulator must be reset by a sync signal after the new freq word is loaded in order for it to work?  How do I generate this sync signal if sif_sync is selected? 

When should the nco_ena and mixer_ena be asserted? Before or after the NCO freq word is configured?

Can the NCO frequency word be changed on the fly? 

Thank you!

  • 0
    TI__Mastermind 44680 points
    Hi Thang
    We have received your question. One of our DAC experts will respond soon.
    Best regards,
    Jim B
  • 0
    TI__Guru* 91947 points

    Thang,

    After configuring the NCO using addresses 0x12 - 0x19, and enabling the mixer and NCO by setting bits 4 and 6 to a "1" in address 0x02, you would then need to synchronize the NCO's. Before you can d o this, you need to decide how you want to do this by picking one of the options in register address 0x1F bits [7:4]. If you want to use a manual SYNC, you would set bit 7 = "1", and bits 5 and 4 to "0" to select SIF_SYNC. Then to perform the SYNC, you would just need to pulse the SIF_SYNC signal from 0  to 1 and back to 0 by writing to a 0 then 1 the 0 to bit 1 of address 0x1F.

    Regards,

    Jim 

  • 0
    TI__Guru* 91947 points

    Thang,

    After loading new values for the NCO (phase and or frequency) you will have to re-sync the NCO for the updates to become active. There is no way to do this on the fly. It does not matter if you enable the mixer and NCO first or after writing the NCO data.

    Regards,

    Jim