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Control VCXO using AuxDAC

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Hello,

In the UG-1828 document there are many ADRV9001 example use cases, almost all of them show that “AuxDAC can be used to control the VCXO responsible for generating the ADRV9001 device clock”.

I cannot find any more information how to control the VCXO using an AuxDAC. In chapter “GENERAL-PURPOSE INPUT/OUTPUT AND INTERRUPT CONFIGURATION” it says how to use the AuxDACs in general, but nothing about VCXO.

Is the VCXO physically connected with any of the four AuxDACs?

Is it possible to test this in TES?

Where can i find more information about?

Please, advise.

gstou

  • Hi,

    I am still looking into how to control the VCXO exactly.

    For now, let me share this information with you:

    • The AuxDACs can be controlled in TES, just program the part first:

    • AuxDAC 3 is connected to the VCXO:

        

    • The VCXO used is the 38.4MHz variant of the GTXO-74V.

    Best Regards,

    Conrad

  • Hi,

    In a test with TES, I was successfully able to control the VCXO. Here is the method I used:

    1) Configure TES to use Clock of 38.4 MHz

    2) Ensure that Clock switch on the eval-board is set to 'Internal'

    3) Program the part and transmit a tone.

    4) Observe the tone on a spectrum analyser:

    5) In the 'Auxilary' tab, enable Aux DAC 3 and set the voltage to 1.7V

    6) Important: Press the 'set code' button. This will not be updated automatically.

    7) Observe the tone on the spectrum analyzer again. Notice that the tone has shifted.

    8) Try again for 0 V and .85V and observe output. The tone is shifted as expected.

    This test shows that since the output tone was shifted (without changing the carrier frequency) then the clock must have been changed. To find the limits and control the VCXO to a desired frequency, please consult the datasheet for the GTXO-74V VCXO.

    Best Regards,

    Conrad

  • Thank you very much Conrad. Your advice is exactly what I needed. I followed the steps you describe above, and I can confirm that there was a small frequency shift.