ADF4002: Output frequency unstable

Hello! I'm using the adf4002 as an int-N PLL with reference frequency = 10MHz and desired output frequency = 80MHz (The specified VCO is CVCO55CL-0060-0110). I think i have set the right value to the corresponding register. The PD polarity bit in initialization latch was set to 0 and 1 seperately to test while the output are both unlocked, jumping from 30MHz to 90MHz. And i have tested one group of Vtune as showned below. Any ideas on solving the problem? Thanks for your help!

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    •  Analog Employees 
    on Mar 29, 2021 10:25 AM in reply to AskLearn

    Hello,

    The first thing I would check is your reference signal. At 10MHz it needs to be a square wave with slew rate 50V/us or greater.

    For register settings you can download the Int N software GUI from the ADF4002 product page. You can then enter controls in GUI for your desired config (e.g. output frequency, PFD fequency, CP current etc.) and it will generate required register settings in hex format