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AD9523-1  Can I precisely adjust output clock frequency with AD9523-1 (EVAL-AD9523-1)?


I would like to inquire if it is possible to achieve precise frequency control with EVALZ - AD9531-1? I'm interested in generating a clock signal that is a multiple of femtosecond laser output pulse rate, which can be something close to 80 MHz, ex. 80.001000MHz. So the frequencies I need would be 160.002000, etc. Initially I thought that precise adjustments can be possible with input frequency, for example, from another DDS board.

I received this board recently and as soon as I started using it I saw that it becomes immune to input frequency change after I write the default setup file in. Is it possible to change this behavior?

Also, may be you can recommend another device that can do the job, if this one is not suitable?

Thank you so much!


  • Hello Dmitri,

    The AD9523-1 will respond to input frequency changes and remain locked, but only over a very limited range (perhaps +/- 50 ppm). The exact range will depend on the pulling range of the VCXO and to a lesser extent, the VCO2 frequency range.

    80.001 MHz is about 12.5 ppm, and that should be ok.

    The first thing I would do is ensure that both PLLs on the AD9523-1 are locked, and then very slowly move the input frequency after locking the AD9523-1 and see how far you can go.

    If you want a PLL with larger tuning range, I recommend the AD9528 and AD9520 family. However, even with the AD9528, you will need a VCXO with higher KVCO than the Vectron CVHD-950 that is on there.

    Another good option is the AD9557, which is a fractional N PLL that can also act as a low jitter frequency synthesizer.

    -Paul Ker

  • Thank you for the quick reply. I'll look closer into AD9557.

  • I think I understand now that AD9532-1 is not going to work, even if I change the external VCXO input to 80 MHz. To match the internal VCO range, the PLL2 divider is a prime number 19, and it is impossible to divide VCO frequency by integers to get initial frequency multiple of 80 MHz.

  • This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

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    EZ Admin