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ADF4108 Eval Board is not Locking

Question asked by Vabya on May 9, 2018
Latest reply on Jul 4, 2018 by Vabya

Currently, I have purchased, ADF4108 Eval-Board (EV-ADF4108EB1Z b). I am trying to run the same configuration what stated in the Eval-Board datasheet before connecting external LF and VCO in-order to get familiar with the eval borad Kit. The specifications are given below for the Loop Bandwidth of 15KHz (as per the datasheet):

VCO frequency=6400 MHz

Reference Frequency: 40 MHz

PFD Frequency: 2500 KHz.

CP-1 and 2: 5mA

PD Polarity: Negative

Prescaler: 32/33

 Int-N software Setting

On powering ON and proving the commands form the AD Int-N software as mentioned above, I can able to see the carrier at the desired frequency. 

VCO/2 output of 6400 MHz spectrum in Spectrum Analyzer with the span of 30 MHz.


I am using 40 MHz Sine Wave TCXO AST3TQ-40 MHz for my REFIN.


I am facing the following issues:


1. The Lock Detect LED D1 is not turned ON. Does it means, PLL is not Locked?

2. IF so, why the PLL is not locking as I have not done any changes on the board except the 40 MHz Sine wave TCXO?

3. On placing Oscilloscope probe on  MUXOUT Test port keeping the MUXOUT to Digital lock, I am getting the 500mV on the scope. What does it imply?

4. What are the other alternatives to check the whether the PLL is locked or not?


I shall be very thankful for your support.