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UCD3138A: Inquiry on Enabling BLANK_B for DPWMC Generation in UCD3138A Full-Bridge LLC Configuration

Martin
Prodigy 170 points
Part Number: UCD3138A
Other Parts Discussed in Thread: UCD3138,

Tool/software:

Hello experts,

I am encountering an issue while configuring a full-bridge LLC with the UCD3138.

According to the datasheet, DPWMC is a signal inside the DPwM logic, and  it goes high at the Blanking B begin time, and low at the Blanking B end time.

If I want to generate DPEMC,after configuring BLANK_B_BEGIN and BLANK_B_END, is it necessary to enable BLANK_B_EN? 

(Because the code provided by TI does not enable BLANK_B,Why? After looking through the datasheet, I'm even more puzzled.)

Looking forward to your insights and guidance.

Thank you.

  • +1
    TI__Expert 4670 points

    Hello Martin,

    You would not want to enable BLANK_B_EN. When you are generating DPWMC, you are only trying to use the COUNTER of BLANK_B_BEGIN and BLANK_B_END to generate a new DPWM signal. If the actual BLANK_B_EN was enabled, then the entire length of the DPWMC would be blanked, which means the CBC would not work. If that is your intention, then you can enable the BLANK_B_EN. But, that is most likely not the case and you would not want to enable the blanking.

    You can look at this E2E post for more info on the DPWMC.

    Regards,

    Jonathan Wong

  • 0 in reply to Jonathan Wong
    Prodigy 170 points

    Thanks,Jonathan.

    But I have another question.

    Both Blank A and Blank B can eliminate the CBC signal during this period.

    What is the difference between BLANK_A_BEGIN and BLANK_B_BEGIN?

    Does this mean that if Blank A and Blank B have the same start and end times, only one of them is needed?

    Are BLANK_A_BEGIN and BLANK_B_BEGIN calculated based on the cycle start point?

    Regards,

    Martin

  • 0 in reply to Martin
    TI__Expert 4670 points

    Hello Martin,

    Blanking A only controls the blanking period for DPWMxA while Blanking B only controls the blanking period for DPWMxB. This allows you to have different blanking times for each DPWM. See the DPWM timing diagrams in the UCD3138 datasheet. The below diagram shows the multi-mode open loop operation in the UCD3138A. Each mode may have different parameters for how the blanking A and blanking B begins.

    Regards,

    Jonathan Wong