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DAC38J84: NCO mode, can adjust the phase between the A and B channel outputs?

Amy Luo
Expert 6895 points
Part Number: DAC38J84
Other Parts Discussed in Thread: TRF3705

Hi team,

I am not familiar with high-speed data conversion devices, could you help answer the following customer questions?

The NCO mode of the DAC38J84, can the phase between A and B outputs be adjusted? How can we adjust this? Could you please explain in detail?

Best Regards,

Amy

  • 0
    TI__Expert 5340 points

    Hi Amy,

    We've received your question and will get back to you as soon as possible. Due to the holiday season, please allow for a delay in response.

    Thanks,

    Aman

  • 0
    TI__Guru 74179 points

    Hi Amy,

    The DAC38J84 has on-chip quadrature modulator correction circuit to adjust the phase of channel A and channel B output (i.e. in-phase and quadrafture phase). See datasheet section below.

  • 0 in reply to Kang Hsia
    TI__Expert 6895 points

    Hi Kang,

    Thank you for your reply.  

    The customer has another question that requires your assistance, could you please give your comments:

    I'm using NCO output now, and then I still want to get a negative frequency? How does this need come true? Is this achieved by adjusting the phase between A and B?

    Best Regards,

    Amy

  • 0 in reply to Amy Luo
    TI__Guru 74179 points

    Hi Amy,

    If the user is using the DAC38J84 along with a RF modulator (i.e. TRF3705), then the NCO can be programmed as a "negative frequency" with I/Q phase in -180 degree fashion. The user can then see the output of the RF modulator with the signal on the "left side" or negative side of the Local Oscillator of the RF modulator. 

    -Kang