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ADF4351 PLL lock problem

Question asked by Raveendra on Oct 30, 2014
Latest reply on Oct 31, 2014 by rbrennan

HI,

 

I wish to know that why PLL is not getting locked, Here i described my configuration and settings.

 

Configuration:

 

Required freq: 1091.2 MHz

Reference freq: 26 MHz

PFD Freq: 26 MHz

Prescalar:8/9

Feedback signal: Divided

 

Register Settings:

 

R0: 1481F8

R1: 8008209

R2: 4E42

R3:4B3

R4:2D003C

R5:580005

 

I am programming with above settings and configuration and i am getting a signal at around 983 MHz with out locking and i tried by changing some configuration like PFD Freq as 13 MHz and small things, But i am not successful.

 

After i measured how much Vtune voltage was generating, i observed as 2.5 V and it is constant for over all different frequencies.

i fed external V Tune voltage eventhough output frequency is same and it is remains same when i increase to further from 0 to 2.2 V. At this moment i observed constant 1.1 V at Vtune voltage when i removed charge pump out connection, is it any device problem or it is default value?

 

Please help me to solve this issue and i attached my block schematic for reference.

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