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AD9516 reference spurs

Dear All,

I am using the AD9516-0 to clock the AD9122.

  • reference frequency = 122.88MHz
  • DAC sampling = 983.04MHz
  • PFD frequency = 61.44MHz

Around the 983.04MHz, I can observe a lot of spurs every 61.44MHz.

What is the maximum reference spurious level for the AD9516?

Thank you

Chris

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  • Hello Paul,

    Thank you for your quick reply.

    Below is the Spectrum for a large sweep that I could measure from one of the 983.04MHz LVEPCL differential output. You can observe the spurs every 61.44MHz (PFD frequency / 2 ).

    • The PFD frequency is 61.44MHz (R=2)
    • The loop filter is very low compare to PFD (166kHz from ADiSimCLK)
    • Internal VCO frequency = 3 * 983.04MHz = 2949.12MHz

    From this clock signal, the DAC output is fine but I was wondering if what I am observing at the AD9516 output is a normal behavior. I will double check your different coments.

    Thank you again.

    PS: Everytime I reprogramm the chip, the level of the spurs change

    Chris

Reply
  • Hello Paul,

    Thank you for your quick reply.

    Below is the Spectrum for a large sweep that I could measure from one of the 983.04MHz LVEPCL differential output. You can observe the spurs every 61.44MHz (PFD frequency / 2 ).

    • The PFD frequency is 61.44MHz (R=2)
    • The loop filter is very low compare to PFD (166kHz from ADiSimCLK)
    • Internal VCO frequency = 3 * 983.04MHz = 2949.12MHz

    From this clock signal, the DAC output is fine but I was wondering if what I am observing at the AD9516 output is a normal behavior. I will double check your different coments.

    Thank you again.

    PS: Everytime I reprogramm the chip, the level of the spurs change

    Chris

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