AnsweredAssumed Answered

Replacing ADF4154 with ADF4151 to gain lock detect and fast-lock

Question asked by Chris3k9 on Nov 21, 2012
Latest reply on Nov 22, 2012 by rbrennan



I have a current prototype design with a ADF4154, the ability to achieve quick settling (<20us) using the fast-lock feature is critical, for production I would like to add a lock detect indication and so am considering a replacement part.


My analysis of the parts with a fast-lock switch and a muxout/LD leads me to the conclusion that my possible choices are:






I liked the look of the ADF4193 with its ultra fast settling time, unfortunately I need an active loop filter to achieve the tuning voltage on my VCO, so I think I have to rule out this part (I've seen the extending the tuning range of the ADF4193 app note).


I discounted the ADF4158/ADF4159 on account of ADIsimPLL 3.43.04 not offering any 'Speedup Type' (I wasn't able to simulate the fast-lock loop)


So that leaves me with the ADF4150 or ADF4151, I can take my RF output from the VCO so not needing 4150's output stage, I think the ADF4151 is most suitable.


Using ADIsimPLL 3.43.04 I can achieve similar performance between my proposed ADF4151 part and my current ADF4154, this is encouraging but I still have a few questions:

  - Are there any pitfalls to my approach of replacing the ADF4154 with the ADF4151?

  - Does the same fast-lock register update sequence apply to the ADF4151 as was in the ADF4154 (i.e. I only need to update the N-divider register to achieve a fast-lock jump)?

  - Out of interest why is it not possible to simulate ADF4158/ADF4159 with fast-lock in ADIsimPLL?


Thanks in advance.