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ADS54J60EVM: clock options

Shuyi Liu
Prodigy 40 points
Part Number: ADS54J60EVM
Other Parts Discussed in Thread: ADS54J60,

I'm using ADS54J60 evaluation board but find the onboard clock cannot satisfy my requirement and would like to use an external clock, but then I find the user guide only mentioned LMK can work in clock distrubution mode with external clock input or clock generator mode with onboard clock, but I wonder can LMK on evaluation board work in clock generator mode with external clock? 

Thanks advance for your help.

  • 0
    TI__Guru* 91947 points

    Shuyi,

    The LMK device on the ADS54J60EVM can work in clock distribution mode.  Attached is an example of using the LMK in clock distribution mode on the ADS54J60EVM. If you decided to use a different frequency, you must make sure the LMK dividers are set properly to provide the correct frequency to the FPGA, the ADC, and SYSREF.

    Regards,

    Jim

    ADS54J60_LMK_CLK_Dist_Mode.pptx

       

  • 0 in reply to jim s
    Prodigy 40 points

    Thank you so much for your reply, I still have a few question to ask:

    1. If I use clock distribution mode, can I just upload lmk_config_external_clock cfg file instead of changing the detail?

    2. Can I use clock generation mode for external clock on evaluation board? Cause I want the ADC work under 1GHz clock but I only have 100MHz clock source, if use clock distribution mode, does that mean I have to find a 1GHz clock source for input clock?

    3. Do you have any guide for mode 4224 or 4211? 

    Thanks advance for your help.

  • +1 in reply to Shuyi Liu
    TI__Guru* 91947 points

    Shuyi,

    You only have to make changes to the clock dividers if they are not correct. For most cases, you should only need to change the SYSREF divider. This is true for the 4224 and 4211 examples attached.

    If using external clock mode, you have to provide an external clock. You can use any external clock frequency that is within the range of the data sheet. This is from 250MHz to 1GHz.

    With the on-board VCXO of 122.88MHz, the LMK can provide the following clock source options for the ADC without any external clock sources:

     245.76MHz, 491.52MHz, 614.4MHz, 983.04MHz.

    The two attached examples are using an external 500MHz clock.  

    Regards,

    Jim

    ADS54J60__LMF_4224_LMK_CLK_Dist_Mode.pptxADS54J60__LMF_4211_LMK_CLK_Dist_Mode.pptx