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

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.