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CCS/TMS320F28035: question about the system clock of the 28035

Houjian Xu
Intellectual 280 points
Part Number: TMS320F28035


Tool/software: Code Composer Studio

The customer has very strict requirements on system clock.

They tested the 28035 using internal crystal， there are few micro seconds error in one minute. I want to know the certain accuracy of the internal crystal?


Therefore, the customer uses the external crystal for the clock source. The external crystal in 28035 EVM is 20MHz. Why not choose the 30MHz crystal, with 2 times the frequency, we can get 60MHz for the 28035 system.

Are there any recommended frequency of the external crystal in 28035?  

 

  • 0
    Intellectual 280 points
    Could you give me some help about the crystal accuracy of 28035.
  • 0 in reply to Houjian Xu
    TI__Guru 62975 points

    Houjian,

    The only published guidelines for the zero-pin oscillator accuracy is a chart of temperature drift from the datasheet.  Realistically, the oscillator temperature compensation procedure should be able to adjust the frequency to around 1% accuracy each time it is executed at a given temperature.

    The datasheet limits the maximum external crystal frequency to 20MHz.  30MHz is only supported as a digital clock signal on the XCLKIN pin.  There is no official crystal frequency recommendation except that it should fall within the datasheet range.  Selecting the same frequency as the EVM would make it easier to run example code on a custom board.

    -Tommy