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AFE7444EVM: Change in AFE REF frequency

Part Number: AFE7444EVM
Other Parts Discussed in Thread: AFE7444, LMK04828


I saw that there are many Ref Frequencies we can see choose between.

I have tried 368.64 MHz and 491.52 MHz, and it worked.

But When I tried 320 MHz and 153.6 MHz also but I am not able to see the PLL lock on EVM.

Please update us on which frequencies, it can Lock.

With Regards,

Ganesh Singh

  • Hi Ganesh,

    Only 245.76 MHz, 368.64 MHz, and 491.52M should be used. Since the EVM has a 122.88MHz crystal installed there is not way to achieve the 153.6 MHz and 320 MHz reference frequencies. The 737.28 MHz should not be used as the AFE7444 has a upper limit of 500 MHz on the reference input. 


    David Chaparro 

  • Hi David , 

    Thanks for your reply.

    You mean to say it is a limitation of LMK04828 VCXO which is 122.88 MHz . 

    But I am not still clear if we change the VCXO to 100 MHz and generate 320 MHz . How we lock the PLL of AFE7444 which is 8847.36 MHz. 

    the PFD freq will be 315.977142857 of AFE . ( Prescaler divider: 4 : M divider: 7 : N divider: 1)

    My question is can we Lock the PLL of AFE with this difference?

    Please correct me if my calculations are wrong.

    With regards,

    Ganesh Singh