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Original question:

Compiler/LMK04208: LMK04208

  • TI Thinks Resolved

Compiler/LMK04208: LMK04828

Prodigy 120 points
uzmeed waheed

Replies: 1

Views: 27

Part Number: LMK04208

Tool/software: TI C/C++ Compiler

Hi 

I need to set up a different clock for the same input 

Say currently I am generating 150MHz clock which variable setting will allow me to generate different clocks like 100MHz, 70MHz or 50MHz

Regards

Uzmeed

Prodigy 120 points
uzmeed waheed
  • Mastermind 23280 points
    Timothy T

    Hello Uzmeed,

    Do you already have a configuration for this device?  Assuming you have programmed a VCO frequency of 3000 MHz, then the only field that needs to be re-programmed is the clock divider.  For example, if CLKout0 = 150 MHz from a 3000 MHz VCO, then CLKout0_DIV in register R0[15:5] must be set = 20.

    • To change to 100 MHz for example, simply re-program CLKout0_DIV = 30.
    • To change to 50 MHz for example, simply re-program CLKout0_DIV = 60.

    Anytime you change the divider, it is possible for the phase of the output clock to change with respect to the other clocks.  If required you can re-SYNC the output dividers.

    • To change to 70 MHz, using a VCO of 3000 MHz is no longer workable as there is no integer division from 3000 MHz to 70 MHz.  To produce this output frequency, you must program the PLL R and PLL N dividers to produce a new VCO frequency which is evenly divisible by 70 MHz.
    • Please refer to datasheet section 9.1.5 for info on PLL programming, note the example in section 9.1.5.1.
    73,
    Timothy

    ____________________________________________________________________________________

    More information Clock and Timing System products: http://www.ti.com/clock-and-timing/overview.html

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