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Original question:

DAC38RF84: TI-JESD204-IP with DAC38RF84

DAC38RF84: Generate frequency hopping tones through internal NCO without SERDIS input data?

Links
Intellectual 2145 points
Part Number: DAC38RF84
Other Parts Discussed in Thread: DAC38RF80, AFE7950

Dear sir,

 

We try to use DAC38RF84 to generate a frequency hopping tones through internal NCO of DAC38RF84.

1. Because we don't require baseband modulation, can the DAC38RF84 generate frequency hopping tones without SERDIS input data? The meaning of SERDIS is the JESD interface. We did not send any digital data through JESD interface.

2. What is the initialization time for DAC38RF84?

Best regards,

Best Regards,
William

  • 0
    TI__Guru* 91947 points

    William,

    The DAC can generate tones without the JESD interface. The DAC38RF84 has two NCO's that you can program and switch between them to get two different output frequencies very quickly. If more tones are needed, the initialization time becomes related to how fast the SPI interface is running. 

    If you select to use the DAC38RF80, this part has 4 NCO's which could allow for faster initialization rates as you could write a new setting for NCO1 while switching between NCO's 2,3 and 4.

    See if these documents help.

    Regards,

    Jim

    DAC38RF80_NCO_freq_change.pptx0882.Multi-tone Gen TI Design.pdf

  • 0 in reply to jim s
    TI__Intellectual 2145 points

    Jim

    My 2nd question is the boot-up time of DAC38RF84 after power up without JESD interface. Because we found the boot-up time of AFE7950 was too long (almost 2 seconds). But we require the boot-up time of DAC38RF84 less than 0.5 seconds. Please advise. Thank.

    Best Regards,
    William

  • 0 in reply to Links
    TI__Guru* 91947 points

    William,

    After power up and issuing a hard reset, the devices requires about 1300 DACCLK cycles to run the auto fuse load. If using a DACCLK = 1GHz, this will be about 1.3us. After this, it will take 12 register writes to get a NCO output on one channel. If running the SPI clock at 10MHz, this should take about 30us.   

    Regards,

    Jim