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HRDB TMS320F28337D, not 180ps?

Tjarco Boerkoel
Expert 1725 points

Dear reader(s),


I'm having PWM1 on 100MHz clock with output PWM1A and PWM1B.

      PWM1A: Set on CNTR==ZERO event, Cleared on CNTR==PWMA event.

      PWM1B: Set on CNTR==ZERO event, Cleared on CNTR==PWMB event.

Both are routed through deadband block:

      PWM1A : RISING EDGE delayed,

      PWM1B: FALLING EDGE delayed, and inverted (complementairy).

Both are running as High resolution :

        n=1;
        EPWM[n]->HRCNFG.bit.HRLOAD      = HR_CTR_ZERO;    
        EPWM[n]->HRCNFG.bit.CTLMODE     = HR_CMP;      
        EPWM[n]->HRCNFG.bit.EDGMODE     = HR_FEP;      
        EPWM[n]->HRCNFG.bit.HRLOADB      = HR_CTR_ZERO;   
        EPWM[n]->HRCNFG.bit.CTLMODEB     = HR_CMP;       
        EPWM[n]->HRCNFG.bit.EDGMODEB     = HR_FEP;       
        EPWM[n]->HRCNFG.bit.AUTOCONV    = AUTOHR_ENABLE;   
        EPWM[n]->HRCNFG.bit.SELOUTB        = HR_NORM_B;   
        EPWM[n]->HRPWR.all                             = 0x8000;     //enable HRES CALIBRATION logic.

        EPWM[n]->HRMSTEP.all                         = 66;    //default value

       EPWM[n]->DBCTL.bit.HALFCYCLE    = 1;

Without DeadBand the PWMs are high resolution, but with DB enabled the edges are not high resolution anymore. They are now changing with 5ns steps instead of the expected ~180ps. It seems that DeadBand degrades the high resolution PWM?

Could someone confirm this, or am I missing things?

Best regards

  • 0
    Expert 1725 points
    Extra question:
    EPWM[n]->HRCNFG.bit.EDGMODEB = HR_DEP; //does not work for rising and falling edges of CMPA and CMPB??
  • 0 in reply to Tjarco Boerkoel
    TI__Genius 10820 points

    Hi Tjarco,

    You can achieve high resolution DB by using DBREDHR and DBFEDHR and configuring HRCNFG2[EDGMODEDB]. Please note that when using HRDB, DBRED and DBFED should be greater than 3 and HALFCYCLE mode must be used.

    Dual edge control should work with high resolution PWM, but please note that CMPAHR may only affect the PWMxA output and CMPBHR may only affect PWMxB output (unless 'swap' is used at the output).

    I hope this helps.

    Hrishi