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TMS320F280049: HRPWM EPWMxSYNC jitter

HS FAE Germany
Mastermind 31670 points
Part Number: TMS320F280049
Other Parts Discussed in Thread: C2000WARE

Hello,

just have a question regarding the note on page 1874 TRM (chapter 18.15.1.5.4.1 High-Resolution Period Configuration):

"When high-resolution period mode is enabled, an EPWMxSYNC pulse will introduce +/- 1 - 2 cycle jitter to the PWM (+/- 1 cycle in up-count mode and +/- 2 cycle in up-down count mode). For this
reason, TBCTL[SYNCOSEL] should not be set to 1 (CTR = 0 is EPWMxSYNCO source) or 2 (CTR = CMPB is EPWMxSYNCO source). Otherwise, the jitter will occur on every PWM cycle with the
synchronization pulse. When TBCTL[SYNCOSEL] = 0 (EPWMxSYNCI is EPWMxSYNCO source), a software synchronization pulse should be issued only once during high-resolution period initialization. If a
software sync pulse is applied while the PWM is running, the jitter will appear on the PWM output at the time of the sync pulse."

- I understand that the jitter is not on the current ePWM HRPWM output but the following ePWM which is synchronized by the EPWMxSYNC pulse?
- doesn't matter if the following PWM is in normal or HR mode?
- jitter has a size of +/-1-2 PWM clocks not HR steps?

Regards, Holger

  • 0
    TI__Mastermind 24095 points

    Hi,


    HS FAE Germany said:
    - I understand that the jitter is not on the current ePWM HRPWM output but the following ePWM which is synchronized by the EPWMxSYNC pulse?

    This is applicable incase you are using HRPWM. Not for normal PWM mode.

    HS FAE Germany said:
    - doesn't matter if the following PWM is in normal or HR mode?

    Doesn't matter for normal PWM mode.

    HS FAE Germany said:
    - jitter has a size of +/-1-2 PWM clocks not HR steps?

    This is PWM clocks, not HR steps.

  • 0 in reply to Subrahmanya
    TI__Mastermind 31670 points

    > This is applicable incase you are using HRPWM. Not for normal PWM mode.
    sorry, I was not clear enough. I mean you are using 2 ePWMs in HR mode. The first ePWM sync the 2nd one (over the SYNCO). Who has the jitter

    > - doesn't matter if the following PWM is in normal or HR mode?
    if the first ePWM is in HR mode and sync the 2nd PWM in normal mode. Any jitter?

    Regards, Holger

  • 0 in reply to HS FAE Germany
    TI__Mastermind 24095 points

    Hi,

    HS FAE Germany said:
    sorry, I was not clear enough. I mean you are using 2 ePWMs in HR mode. The first ePWM sync the 2nd one (over the SYNCO). Who has the jitter

    second one receiving the sync will have the jitter

    HS FAE Germany said:
    if the first ePWM is in HR mode and sync the 2nd PWM in normal mode. Any jitter?

    No. only if 2nd PWM in HR mode - 2nd PWM will see jitter. If 2nd PWM in normal mode, then there will be no jitter.

  • 0 in reply to Subrahmanya
    TI__Mastermind 31670 points

    Hello Subrahmanya,
    is it planed to fix the issue in future devices?

    Regards, Holger

  • 0 in reply to HS FAE Germany
    TI__Mastermind 24095 points

    Hi,

    These is no issue here as such. No issue if 2nd PWM in normal mode.
    Even if 2nd PWM is in HR mode, there is a way to attain synchronization as shown in the example below.
    C:\ti\c2000\C2000Ware_3_04_00_00\device_support\f2837xs\examples\cpu1\hrpwm_deadband_sfo_v8