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DAC39j82 full complex mixer sync problem

Hao Liu
Prodigy 95 points
Other Parts Discussed in Thread: DAC39J82

Hi,

I am trying to use two DAC39J82 to transmit two identical sinusoidal signal.

By turning off the full complex mixer inside the DAC39J82. I see that the two sinusoidal signal are always in phase between power cycles.

By turning on the full complex mixer inside the DAC39J82. Between power cycles, sometimes I see the two sinusoidal are in phase, sometimes I see the two sinusoidal are 180 degree out of phase. the odds is 50 percent.  I am using the sync_out from JESD to sync the nco and mixerab. I have been stuck for a while trying to find out why but fails. by the way, I am using the full complex mixer, and turned off the QMC module.

Do you have any suggestions?

Thanks a lot.

Hao

  • 0
    TI__Guru* 79314 points

    Hao,

    We may need to look into further on the SYNC_OUT feature when used to sync the NCO and mixerab. 

    There are other sync method such as using sif_sync feature through SPI writes. Could you try enabling the sif_sync feature and toggle the sif-sync bit via SPI to see if the issue is resolved?

    -Kang

  • 0 in reply to Kang Hsia
    Prodigy 95 points
    Hi, Kang,

    Thanks a lot for the reply. unfortunately, our application requires to sync the two DAC39J82 simultaneously, and sync_out from JESD or sysref is the only source that can be fed into the two DAC39j8s at the same time.
    The sif_sync signal between the two dacs will have a huge delay because of the slow nature of SPI communications running on single thread of the embedded program.

    I really need to use this SYNC_out feature, any recommendation is much appreciated.

    Thanks a lot.

    Hao