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TMS320F28374S: Glitch occurs when AQSFRC is used to force low

Jordan Zhou
Genius 9340 points
Part Number: TMS320F28374S

Hi,

Did you face PWM glitch when AQSFRC is used to force low?

The glitch is only happened when AQSFRC is used.

The glitch lasts about 100~200ns.

There are continuing glitch after AQSFRC used. 

Thanks a lot.

Br, Jordan

  • 0
    TI__Mastermind 24095 points

    Hi Jordan,

    there is no glitch issue I'm aware of regarding AQSFRC.
    Also, 100-200ns doesn't look like a glitch. It's several clock cycles.
    So, i suspect this would be a PWM configuration issue.

    When in software are you forcing the PWM output using AQSFRC?
    Note that the AQSFRC action could be overridden by other events, if configured, to change PWM output.
    In case you want a continuous force, you should use AQCSFRC.

  • 0 in reply to Subrahmanya
    TI__Genius 9340 points

    Sub,

    We tried again with AQCSFRC like:

    The issue is still there, without any improvement.

    What could be the issue?

    Thanks a lot.

    Br, Jordan

  • 0 in reply to Jordan Zhou
    TI__Genius 9340 points

    Sub,

    Let me clarify the issue in details: the issue occures only when the force is used, and occures only one time, the pulse is between 10ns~200ns.

    1) strBoostCtrCpu.fBoostOut[BoostCPU_ID2] is a globla variables. Its value will be passed to CMPA or CMPB;

    2) When the value is lower than 19, they'd like to force the output on PWMA and PWMB;

    3) CMPA and CMPB are shadowed, load on zero and period;

    4) Global reload is not used;

    5) The PWM configuration is as below: RLDCSF with value 2 or 3, the issue is the same. 

    Thanks a lot.

    Br, Jordan

  • 0 in reply to Jordan Zhou
    TI__Mastermind 24095 points

    Hi,

    What is the current state of the PWM when the output is being forced high using AQCSFRC?

    In immediate mode, a continuous force takes effect on the next TBCLK edge. In shadow mode, a continuous force takes effect on the next TBCLK edge after a shadow load into the active register.

    So I suggest you use RLDCSF=3 for immediate mode.

    Once the continuous force takes effect and PWM reaches a desired state - Only Trip logic can change the status of the PWM o/p.
    For your testing, you can disable the trip and check if there is any issue in the trip configuration that is causing this behavior.

  • 0 in reply to Subrahmanya
    TI__Mastermind 24095 points

    Hi,

    Did you get a chance to try above? If so, please update your observation or close this thread.