• State
  • Locked Locked
  • Replies 2 replies
  • Subscribers 7 subscribers
  • Views 107 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

AFE7444EVM: Change in AFE REF frequency

ganesh singh1
Intellectual 390 points
Part Number: AFE7444EVM
Other Parts Discussed in Thread: AFE7444, LMK04828

Hi,

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

  • 0
    TI__Expert 5980 points

    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. 

    Regards,

    David Chaparro 

  • 0 in reply to David Chaparro
    Intellectual 390 points

    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