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TMS320F28379D: TMS320F28379D

vadim piskun
Expert 2230 points
Part Number: TMS320F28379D
Other Parts Discussed in Thread: C2000WARE

Hi

I need to combine two EPWMs with different frequencies together. I could not find in the data sheet their EPWM output circuitry. If I tie them together, the output is not symmetrical, simulation of two pulse generators with 50 Om internal impedances tied together does not show such asymmetry.

Thanks vadim

  • 0
    TI__Expert 6020 points

    Hi vadim,

    First, Assuming your both time periods satisfy=> T(low freq.)= N* T(high freq.) then you can use sync feature on PWMs to have the same rising and falling edges. This removes uneven pulses. 

    For synchronization between ePWMs  technical reference manual

    examples in C2000 ware: C:\ti\c2000\C2000Ware_4_03_00_00\driverlib\f2837xd\examples\cpu1\epwm/ex3..

    I dont think you have a proper offset for the resultant waveform. The offset has to be 3.3/2 which i dont see on the scope outputs. Can you share your code, how are you acheiving this and also for which application you are using this pulses for?

     Best Regards,

    Uttam Reddy Pailla

  • 0 in reply to Uttam Reddy Pailla
    Expert 2230 points

    Hi Uttam,

    I use syscfg file to set the frequencies. I can send this file if you provide email address. This is PWMs that goes from 0 to VCC. It does not use any modulation just fixed rectangular outputs. "I dont think you have a proper offset for the resultant waveform".  how can i set the offset for PWM?

    thanks vadim

  • 0 in reply to vadim piskun
    TI__Expert 6020 points

    Hi Vadim,

    the ePWM uses UP count mode only. where your Action Qualifiers are set wrongly. At CMPA  it goes high but it cannot go low at down

    you can either use PRD/ZERO to change the AQ state. or else can change to up-down count mode. 

    Thanks & Regards,

    Uttam

  • 0 in reply to Uttam Reddy Pailla
    TI__Expert 6020 points

    Hi vadim, 

    Can you ellaborate your purpose to generate such waveforms? I can check with other experts based on the application. 

    I believe that could only be possible with analog circuitry, but with the digital signals will either be 0 or 3.3V (i.e., 0 or 1). you cannot combine such waveforms and have a 1.65V offset. 

    2. how did you generate the R1? I believe C1 and C2 are generated by PWMs but not sure on R1.

    Best,

    Uttam