MK10 (72MHz) External clock selection

[donikuy]

We need to select an external clock for a MK10 (72MHz).

What are the advantages/disatvantages of different external clock speeds when generating the internal speed.

We are trying to achieve 72MHz.

[kerryzhou · Accepted solution]

Hi Ylber Doniku,

      Thank you for your interest in Freescale kinetis product, I would like to provide service for you!

      If you want to use the crystal oscillator,  you can choose 3 to 32Mhz external crystal oscillator, this should use the internal OSC logic module, this module will have the power consumption, but to the external circuit, it is simple and low cost.

      If you want to use the external reference clock, the max input clock frequency is 50Mhz, and you should choose the proper frequency which can get 72Mhz.

the input clock duty cycle should in 40% to 60%.  This method don't need use the internal OSC logic module, so it can save the OSC consumption, but you need to use other clock generator component give the correct frequency.

    Actually, if you want to achieve 72Mhz, just refer to the TWR-K20D72M schematic, choose the external 8Mhz crystal is ok:

http://cache.freescale.com/files/32bit/hardware_tools/schematics/TWR-K20D72M_SCH1.pdf

Wish it helps you!

If you still have question, please contact me!
Have a great day,
Jingjing

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