• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 82 subscribers
  • Views 735 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

CCS/LAUNCHXL-F28379D: How to select frequency of different operations in high switching frequency converter?

Utsav Sharma12
Intellectual 420 points
Part Number: LAUNCHXL-F28379D

Tool/software: Code Composer Studio

Hello Team TI,

When I am working for high frequency converters, how to decide the frequency of different operations and interrupts in F28379D.

For illustration, I am working with 100kHz converter then what should be the sampling frequency of cpu timer (using Nyquist criteria?).

    InitCpuTimers();                                       // Initialize Cpu Timers

    ConfigCpuTimer(&CpuTimer0, CPUFREQ_MHZ, 100);          // Configure Cpu Timer0 to interrupt at specified sampling frequency

    CpuTimer0Regs.TCR.all = 0x4000;                        // Start Cpu Timer0

Moreover, after selecting sampling frequncy, what should be the ADC start of conversion signal frequency and acquisition window time period?

I think that the answer should be,  Frequency of acquisition window > ADC start of conversion signal frequency > sampling frequency of CPUTImer > operation frequency (epwm frequency). Kindly correct me if I am wrong.

  • 0
    TI__Mastermind 37760 points

    Hi Utsav,

    It might help to also check the ADC timing diagram to see the relationship of start of conversion, acquisition window and end of conversion.  The sequence for a proper conversion is to have a start of conversion (SOC), allow for enough tSH, and wait for tEOC as illustrated in the timing diagrams.  The end of each tEOC, users have the option to trigger interrupts to service them (by reading out the converted values from the ADC).  Also note that the start of conversion can be triggered from different sources (SW, EPWM and CPU Timers - see TRIGSEL field in the ADCSOCxCTL registers from the TRM).  That said, the interrupts that need to be serviced to read out the ADC results should also occur upon a conversion is complete for the duration of tSH+tEOC.  ADC triggers from any of the trigger sources should occur faster than the frequency of the sampled signal (and meet Nyquist criteria).

    Not sure what you meant by sampling frequency of CPU timer and operation frequency (epwm frequency).  Can you elaborate on these?

    Regards,

    Joseph