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HMC7044 PLL2 not locking

Question asked by on Sep 15, 2017
Latest reply on Sep 20, 2017 by kpeker



I am using HMC7044 in my customised design. I have disabled PLL1 and using only PLL2. I am feeding a 100MHz clock from external crystal to HMC7044 through OSCIN pin. But PLL2 is not locking. What may be the reason. 


I have checked the 100MHz clock at OSCIN pin and it looks fine.

I am checking 0x7D (bit 0) register for PLL2 lock status. I am reading 0x02 as readback data of this register.


I have another HMC7044 on the same board where PLL2 is locking and reading back 0x7D register gives 0x13 (bit 0=1) . This shows that PLL2 is locking on 2nd HMC7044.


Please let me know what may be the reasons for PLL2 not locking. Any help is much appreciated.