PLL cricuit with ADF4106 Problem [hlp]

[No one]

PLL Problem [hlp]

Hello Everyone;
I have designed a PLL cricuit with ADF4106 of Analog Devices. But a problem has occured: the PLL doesn't work, it stays in start of the VCO band for N = 0 and goes to the end of VCO band for greater values of N! What's the problem? May PLL IC has been damaged? Is there any problem with reference signal (the reference is supplied by a TCXO)? Please help me.

 

[yendori]

Re: PLL Problem [hlp]

It could be that the TCXO Vpp is too low, so the PLL has nothing to compare to.

Or more likely, you are missing something in the registers. Make sure the polarity of the detector is set correctly.

 

[kspalla]

PLL Problem [hlp]

Check the Voltage at the charge pump then compare it with the VCO control voltage. you can even go to debug mode wher you can select the output of MUX.

 

[No one]

Re: PLL Problem [hlp]

Hello Everyone;
My PLL now works. The problem was occured because of false programming a bit.
Now how I can improve its phase noise? Is schielding necessary?

 

[BigBoss]

Re: PLL Problem [hlp]

Hello Everyone;
My PLL now works. The problem was occured because of false programming a bit.
Now how I can improve its phase noise? Is schielding necessary?

Phase Noise is depended on
-VCO
-PLL Reference Source
-Divider ratio
-Loop Filter
-Charge Pump Current
etc..
The question is:
Which PN should it be improved ?? Far PN or Close one..
In-band or Out-band ???
Which offset at ???
What Frequency ??

 

[ithink]

PLL Problem [hlp]

if improve pn in band, pls decrease loop BW,But too small may cause noise worse! so pls design divider,CP and vco more carefully!