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TMS320F28377D: PWM duty 0% and 100% support

Jordan Zhou
Genius 10200 points
Part Number: TMS320F28377D


Hi,

Does F2837x ePWM support 0% and 100% duty by setting CMPA and CMPB to 0 and TBPRD, in up-down mode?

In the user guide, it's said that:

1) symmetric PWM, CMPA and CMPB should be limited between 1~TBPRD-1;

2) asymmetric PWM, the other case.

But, in my original understanding, type 4 ePWM can support 0% and 100% directly, without any walk around like F28335.

Thanks.

Br, Jordan

  • 0
    TI__Genius 15260 points
    Hi Jordan,

    It is possible without a workaround. Please see Figure 14-24:

    www.ti.com/.../spruhm8f.pdf

    Regards,
    Kris
  • 0 in reply to Kris Parrent
    TI__Genius 10200 points
    Kris,
    Thanks for your info.
    Figure 14-24, we already saw. But the description is not serious, like "This means there will always be a pulse of at least one TBCLK cycle in a PWM period which, when very short, tend to be ignored by the system. ".
    My understanding is that, there's no possible to get pure 0% and 100% by setting CMPA=0 or CMPA=TBPRD, in up-down mode, CMPA load on ZERO and PERIOD. Is that correct?
    In customer's system, 1 TBCLK cycle is not possible to be ignored.

    Br, Jordan
  • 0 in reply to Kris Parrent
    TI__Genius 10200 points
    Kris,
    Customer already shipped more than 10K units. All of the codes, 0% and 100% are implemented by setting CMPA=0 and CMPA=TBPRD.
    Till last week, there's no issue.
    This Monday, they found one unit, which had the issue. If they limited CMPA between 1 and TBPRD-1, the PWM output well. If no limitation, there's the issue. In their system, they need 0% and 100%. They prefer to achieve by setting CMPA=0 and CMPA=TBPRD directly.
    Thanks a lot.
    Br, Jordan