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C2000WARE: Do you need to program CMPB and CMPBHR if using active high complimentary mode?

Joel Holland
Intellectual 765 points
Part Number: C2000WARE

Hi all,

I am using active high complimentary mode programming and from the examples it seems that one does not need to physically program the CMPB register, just the CMPA register and then the MCU can handle the generation of the B output of the PWM by using the edge delays that are programmed and the existing CMPA value. 

Is this true, or does one need to program both the CMPA and CMPB registers regardless of the POLSEL bit?

If directly programmed, how to ensure that the duty cycle signals have the right delays, and never overlap? To ensure that shoot-through type conditions do not occur.

Thanks!
Joel

  • 0
    TI__Mastermind 19795 points

    Hi Joel,

    Could you provide the device name/model, software example being used, and any additional details regarding your setup?

    This will allow us to provide the best assistance possible, and to route you to the correct primary owner.

    Regards,

    Vince

  • 0 in reply to Vince
    TI__Mastermind 24095 points

    Hi,


    Yes, you need to program CMPBHR though you are operating in Active high complimentary mode. Because CMPBHR is tied to PWMB output - though it's a complimentary output. You can program same value as CMPAHR

  • 0 in reply to Subrahmanya
    Intellectual 765 points

    Hi,

    That doesn't make sense to me - if for example I want 5% PWMA output, and 95% PWMB output, why would I program CMPA and CMPB to be the same values? Is this only true for a 50% duty cycle scheme? 

    How would you program if you wanted say 5%? How would one ensure they never cross-over and shoot-through?

    Best,
    Joel

  • 0 in reply to Subrahmanya
    Intellectual 765 points

    Directly from the technical manual: 

    "Generating appropriate signal pairs (EPWMxA and EPWMxB) with dead-band relationship from a single EPWMxA input"

    Are you sure we need to program both if the deadband module performs this funciton above??

    Best,
    joel

  • 0 in reply to Joel Holland
    TI__Mastermind 24095 points

    Hi,

    Yes, If you are not using HR operation then updating CMPBHR is not needed. Only if you are using HR operation it is required and in HR mode, PWMB is CMPBHR.

  • 0 in reply to Subrahmanya
    Intellectual 765 points

    To clarify, if I am not using HR mode, I do not need to program neither CMPB nor CMPBHR. 


    If I am using HR mode, I need to program CMPBHR, but not CMPB? Or I need to program both?

    If I need to program both in active high complimentary mode, how do I ensure I do not get overlap in my signals? 

  • 0 in reply to Joel Holland
    TI__Mastermind 24095 points

    Hi,

    Joel Holland said:
    To clarify, if I am not using HR mode, I do not need to program neither CMPB nor CMPBHR. 

    Yes.

    Joel Holland said:
    If I need to program both in active high complimentary mode, how do I ensure I do not get overlap in my signals?

    this is guaranteed by dead band configuration. There will not be overlapping signals in case AHC (active high complimentary mode)

  • 0 in reply to Subrahmanya
    Intellectual 765 points

    Hi Subrahmanya,

    Unfortunately this is not the case with my signals. Despite using active high complimentary mode,there is still slight crossovers between my gate driver signals. 

    Is there a reason this may be so in the PWM configurations? I have tried to increase and decrease the dead-times yet still suffer this problem.