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LAUNCHXL-F280049C: PCMC closed loop application configuration does not work for Active load.

venkatesh chilapur
Mastermind 6460 points

Part Number: LAUNCHXL-F280049C
Other Parts Discussed in Thread: C2000WARE

Hi,

I have followed the above steps from the PCMC application example as shipped by TI.

In the closed loop PCMC configuration however enabling the active load sets the trip flag to be set and the output is zero.

While I am using the same exact hardware why do i see a different behavior from the one mentioned above?

  • 0
    TI__Guru 62975 points

    Venkatesh,

    Can you describe what happens when you try to clear the trip condition using the sequence in the NOTE?

    -Tommy

  • 0 in reply to tlee
    Mastermind 6460 points

    Hi Tommy,

    Sure, here are the steps I follow:

    C2000 DPS BoosterPack Rev 2.1 is connected to LaunchXL-F280049C.

    I launch CCS 9.3.0 and import the buck_F28004x project from C:\ti\c2000\C2000Ware_DigitalPower_SDK_3_00_00_00\solutions\tidm_dc_dc_buck

    Followed by launching the configuration and selecting the Lab 4: for PCMC closed loop operation and launchpad site 2.

    Then I build the code and download the same to target. Note: Before I click resume in the CCS debugger, I turn the 9V supply followed by SW1 to ON.

    When I click resume, I have the PCMC closed loop running and could see the above reading which are good!

    Then I come to step 4, i.e enable continuous active load mode:

    The moment I enable the Active load as captured above, the sensed voltage drops to zero. I could see the waveform in DSO going to 0%DC for PWM-HI. Also we can see the Tirp Flag is set.

    HTH,

  • 0 in reply to venkatesh chilapur
    TI__Guru 62975 points

    Venkatesh,

    It seems like a false trip to me.

    Can you try to execute the trip clearing sequence while in this state with BUCK_activeLoadEnable enabled?  If it continues to trip, you can try to increase the BUCK_iOutTripSetRef_Amps trip threshold to 6A.

    -Tommy

  • 0 in reply to tlee
    Mastermind 6460 points

    Hi Tommy,

    Thank you.

    Executing trip clearing sequence alone does not help. however increasing the Reference Amps threshold to 7.2A (Not even 7A helps) seems to make the difference. But the output voltage is not regulated properly. Sometimes the reading dips to 1.4V. Here is the snapshot of the same.

    Please let me know if this is expected observation? Meantime I will try to increase the current limit in MATLAB and see if I can reproduce this behavior.

  • 0 in reply to venkatesh chilapur
    TI__Guru 62975 points

    Venkatesh,

    BUCK_activeLoadContEnable should be enabled as well for stability. The dynamic load setting is not recommended for PCMC.

    -Tommy

  • 0 in reply to tlee
    Mastermind 6460 points

    Hi Tommy,

    Setting BUCK_activeLoadContEnable on top does more harm than good. Are you suggesting that Active load should not be enabled when running PCMC. I am not sure why do i see different experimental results than what is claimed in the TI user guide.

  • 0 in reply to venkatesh chilapur
    TI__Guru 62975 points

    Venkatesh,

    Both BUCK_activeLoadEnable and BUCK_activeLoadContEnable should be enabled at the same time.

    I see in your 1.47V screenshot that your BUCK_vInSensed_Volts reading is down to 6.5V.  Can you check your 9V DC supply to see if it is stable during operation?

    -Tommy