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TMS320F2800157-Q1: ePWM TMS320F2800156

Chris Willis
Intellectual 300 points

Part Number: TMS320F2800157-Q1

NOTE: I couldnt find a part number for the TMS320F2800156 but that is the part I am working with/investigating.

What range of frequency is available for the ePWM output?

What is the resolution of the ePWM output?

What is the maximum current available from the ePWM output?

Thank you

  • 0
    Intellectual 300 points

    FYI we are using external crystal: XTAL is 20MHz and our clock is presently 120MHz

  • 0
    TI__Mastermind 20416 points

    Chris,

    The frequency of PWM events is controlled by the time-base period (TBPRD) register and the mode of the time-base counter. The time increment for each step is defined by the time-base clock (TBCLK) which is a prescaled version of the ePWM clock (EPWMCLK).


    The effective resolution for conventionally generated PWM is a function of PWM frequency (or period) and system clock frequency : PWM resolution (%) = Fpwm /Fepwmclk x 100%. If the required PWM operating frequency does not offer sufficient resolution in PWM mode, consider using HRPWM.

    You can find more details on frequency calculation for each mode in section 14.4.3 Calculating PWM Period and Frequency in TMS320F280015x Real-Time Microcontrollers Technical Reference Manual. 

    For EPWM Current output please refer to the table 6.6 Electrical Characteristics in TMS320F280015x Real-Time Microcontrollers datasheet.

    Thanks,

    Prarthan.

  • 0 in reply to Prarthan Bhatt
    Intellectual 300 points

    I was hoping more for a numerical range. Something like :

    The ePWM frequency can be set anywhere between 0 to the system clock (which in your case is 100MHz) in increments of 1kHz. 

    Also the 156 doesnt have the HRPWM option.

    And we are not using the small steps shown in Figure 14-6. We are using the traditional PWM square style like below:

    Is there any additional information I can provide to help find the answer to this?

  • 0 in reply to Chris Willis
    TI__Mastermind 20416 points

    Chris,

    The maximum frequency possible with epwm is 50MHz (or system clock if it is less than 50Mhz) captured in section 6.15.1.2 ePWM Electrical Data and Timing in TMS320F280015x Real-Time Microcontrollers datasheet.

    The granularity will depend on what mode you are using according the formula below:

    Granularity in fpwm is proportional to f_tbclk that is chosen (In your case its 120Mhz) because TBPRD value can only change with granularity of 1.

    TBPRD = .5* (FTBCLK/FPWM) for Symmetric PWM (Up-down count)
    TBPRD = (FTBCLK/FPWM) -1 for Asymmetric PWM (Up count or down count)

     



    Thanks,

    Prarthan.

  • 0 in reply to Prarthan Bhatt
    Intellectual 300 points

    I am using the 156 model so I believe f_tbclk would be 100M instead of 120

    so PWM frequency = 0.5 * 100M / n   | n=1,2,3,4,....

    I could get a PWM frequency of 24414.0625Hz ~24.4kHz if I select n = 2048 

    Is that correct?

  • +1 in reply to Chris Willis
    TI__Mastermind 20416 points

    Chris,

    That's correct. You can also set f_tbclk by configuring Time base clock TBCLK = EPWMCLK / (HSPCLKDIV * CLKDIV)

    Refer to TBCTL Register Descriptions for more details