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ADF4350 unable to lock although registers data is correct

Question asked by Mahesh04 on Aug 2, 2018

Hello everyone,


I wanted to use ADF4350 for signal generation purpose. I went through datasheet, forums and evaluation software and hardware details and programmed registers properly but i am unable to lock PLL. I have following questions


1) What is the maximum clock rate with which SPI to be run. Minimum is around 20ns- 40ns mentioned in datasheet. I am running it with 1 ms rate, would that be a problem?

2) I am writing R5 and making LE high then LE false and loading another register and the process is continues till all the registers written. Will it be continuously writing or one time is enough to lock PLL?

3) What are troubleshooting methods to know whether i am writing proper registers ? I have installed analog devices ADF435x software and opened and i found few default registers. I have entered those register values and ran but still not able to lock PLL. Anybody can provide register values which are working for?

4) Before PLL lock can we see any intermediate results? like REF, mux out etc.... 


Thanks in advance,


Radar Systems Engineer