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ADF4351 locking problems

Question asked by PierLuc on Apr 7, 2017
Latest reply on Apr 12, 2017 by PierLuc


my ADF4351 circuit is not locking on some frequencies. When this happens, I noticed that VTUNE voltage is at VCC (3.3V). When my PLL is locking on others freqeucies, VTUNE is well controlled and able to lock without notable oscillations. 

Is someone able to explain me what can cause that ? 


I tried A LOT of thing without any results. 

for information, my PLL reference is at 10 MHz. Is that a problem ?