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Hmc829 isolation between analog and digital inside the chip


I'm using HMC829 RF PLL evaluation board I run the configuration from examples that Hittite provided,

at the RF output I see some spurious at different places that running through small band =1MhZ when I click on read lock register(12h) with some period between the clicks. I use REF=100[MhZ] and run at 3GhZ at the output. It looks like some isolation problem between analog and digital parts inside the PLL it's important me to say that at same conditions I never met the problem in other  HMC840,HMC838 PLL's.

Please suggest what a solution for this issue cause I want to use this pll in system and run check for lock at least every second.

Thank you.