I am testing the ADF4351 now , and I have the same confusion.
Firstly , I can get the lock time lower than 40us by setting 100kHz loop bandwidth and DB28(phase adjust) to 1 in Register 1. But then the LO can only be locked in 10MHz bandwith (such as 500MHz to 510MHz).
Secondly, if I set DB28 to 0 in R1, then the LO can be locked within 100MHz at least , but the lock time is worse to 250us.(this is the same result for ADF4350).
Thirdly , I try to use the fast lock mode , but still the lock time can not be improved.
My purpose is to jumping the LO for at least 100MHz in 150us lock time.
Can any expert do me a favor to tell me whether my purpose will work by using ADF4351?