AnsweredAssumed Answered

ADF4351 fractional spurs

Question asked by Uriasarussi on Aug 3, 2011
Latest reply on Aug 11, 2011 by Uriasarussi

Hi  specialist,

 

When I set the synthesizer for 2500.5MHz on my board end same on EVAL-ADF4351EB1ZU4 (attach set up for ANALOG GUI)
once fractional spurs going up roughly 36dBc and second time up to 45dBc and back again without any cyclical legal.

Why it’s happened?

My registers:

5=00580005

4=00814024

3=00800003

2=02004442

1=08000141

0=003E8008

My reference frequency: 10MHz

My Board details:

Icp = 0.938mA

C1=180pF

R1=2kΩ

C2=2.7nF

R2=3.6kΩ

C3=82pF

Loop BW=70.6kHz

Phase=48.3deg

And same phenomenon with-

Icp = 0.938mA

C1=220pF

R1=1.8kΩ

C2=3.3nF

R2=3.4kΩ

C3=100pF

Loop BW=63.6kHz

Phase=47.9deg

 

Best Regards

-----------------------

Uria Sarussi

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