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EV-ADF4001SD1Z settings issue

Question asked by Vimal@Accord on Sep 22, 2017


The task is to lock 10MHz OCXO to a standard rubidium using ADF4001.  I am using EV-ADF4001SD1Z evaluation broad.  


Let me tell the jumper settings on the broad.  

LK1 - B

LK2 -  B

LK3 -  B VDD - 3V

LK4 -  A Vvco -  5V

LK5 -  A Vp -  5V

Instead of a VCO, an OCXO is used. Initially for the OCXO the supply was from the broad but the voltage dropped less than 3V. So external power supply is used.  


A 2nd order passive loop filter was designed using ADIsimPLL.  The values of the components are 

C1 -  10nF, C2 -  47nF, R1 -  1M. Loop Bandwidth is 9.98Hz and phase margin is 44.5 degrees.  

All the required components are placed on the broad. 


The settings while designing the loop filter and in Int-N software are Output frequency is 10MHz, phase detector frequency is 25KHz, Reference frequency is 10MHz, Kvco - 6Hz/V, Charge pump current is set to maximum 5mA.


To start with, a signal generator was used instead of rubidium as reference.  I have programmed all latches using Int-N software.  When I probe on the output of charge pump(CP) , it was observed to be an constant voltage. Even when I change the reference frequency by few Hz,  there is no variation at the output of CP.  I doubted the SPI communication but it's working fine. 


The observation was there is no difference at the output of CP,  even if I program or not. The output is constant (I am probing at C1).  


Is there any other settings I have do?