# LTC6946-1 loop filter bandwidth

I'm using the LTC6946-1 to output a 2.5 GHz clock.

The LTC6946-1 only locks sometimes when using an open-loop bandwidth of 1440 kHz (with Fpfd = 163840 kHz). This should work (according to datasheet and PLLWizard) since the open-loop bandwidth is 11 times lower than Fpfd.

The LTC6946-1 always locks if I lower the open-loop bandwidth to 130 kHz.

I can use an open-loop bandwidth that is less than 1440 kHz, but I want to be sure that the LTC6946-1 always will lock. How can I make sure that my chosen bandwidth will work? Can it be simulated or calculated or do I have to experiment some and then back off?

My settings:
Fref: 16.384 MHz
Fstep: 16.3840 MHz
Frf: 2490.368 MHz
R div: 1
N div: 152
O div: 1
FILT: 3
LKWIN: 3 ns
B cnt: 24
Icp: 11.2 mA

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