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TMS320x280x - ePWM Deadband Submodule

Jordda
Intellectual 665 points

Hi,

Please refer to page 52 in Application Note SPRU791F. My question is about the register setting. I want EPWMxA floating. I have set the following setting, but I'm not sure if EPWMxA will be floating. Please kindly advice me. Thanks!

// Only EPMW1A is activated. EPMW1B is NOT activated.

PWM_setDeadBandInputMode(myPwm1, 3<<4 );  // S5:S4 = 1:1
PWM_setDeadBandPolarity(myPwm1, 0<<2);        //  S3:S2 = 0:0
PWM_setDeadBandOutputMode(myPwm1, 3 );     //  S1:S0 = 1:1

  • 0
    Expert 1725 points

    Hi Jordda,

    What doe you mean by floating? Your IO pin floating (HiZ or always High without PWM or..?).. 100% Duty cycle..Or not synced with other PWM modules..?

    Best regards,

    Tjarco

  • 0 in reply to Tjarco Boerkoel
    Intellectual 665 points

    The floating means HiZ here and no output anything

    EPWMxA is always connected with the certain pin of another IC. Although it's connected with other IC (IC-A) physically, we want EMPWMxA does not output anything signal sometimes so as not to bias high or low for IC-A.

    Let me narrow down the question. What will happen if the register setting is as the following? Does it output any signal like low or high?

    // Only EPMW1A is activated. EPMW1B is NOT activated.

    PWM_setDeadBandInputMode(myPwm1, 3<<4 );  // S5:S4 = 1:1
    PWM_setDeadBandPolarity(myPwm1, 0<<2);       //  S3:S2 = 0:0
    PWM_setDeadBandOutputMode(myPwm1, 3 );    //  S1:S0 = 1:1

  • 0 in reply to Jordda
    Expert 1725 points

    Hi Jordda,

    I would say that EPWMxB output is low, because it's not set by the PWM comparator (default state) and you've bypassed the polarity block.

    High Z is not a state of the GPIO (GPIODAT 0 or 1). Maybe you could try to disbale the pull-up of the PWM-GPIO and set GPIO to input?

    Tjarco

  • 0 in reply to Tjarco Boerkoel
    Intellectual 665 points

    Switching between ePWM and GPIO mode may not be reached in a very short period. Do you have any method to switch between ePWM mode and Floating mode in a very short period? Thanks !!

  • 0 in reply to Jordda
    Expert 1725 points

    Hi Jordda,

    Maybe you should take a look at the tripzones.

    Specify the tripping action taken when a fault occurs: Force EPWMxA and/or EPWMxB to a high-impedance state

    http://www.ti.com/lit/ug/sprug04a/sprug04a.pdf Page 18.

    Trips can be triggered externally or by software force bit.

    Tjarco

  • 0 in reply to Tjarco Boerkoel
    Intellectual 665 points

    Hi Tjarco,

    It's an useful advice for me. I will try it. Thanks!