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TPS54560B: About Output Voltage 26V. Duty 100% operation.

Masazumi Ishii
Genius 3945 points

Part Number: TPS54560B

Hello.

I have a question about TPS54560B.

Input: 26V-60V
Output 26V 4A
Duty: Near 100%.
Want to work with

The TPS54560B can handle up to 21.5V.
However, at 26V output, it does not work at 100%.
Is there a way to make it work?

Are there any devices that can operate under these conditions?
Thank you.
  • 0
    TI__Expert 8245 points

    Hi,

    Do you mean when you apply a 26V input, then the output is 21.5V? Or just find when the output is 26V the duty cycle is not 100%?

  • 0 in reply to Iven Su
    Genius 3945 points
    Hello

    The questions are listed again in the attachment.

    please confirm.

    Thank you.
    TPS54560B.pdf
  • 0 in reply to Masazumi Ishii
    TI__Expert 8245 points

    Hi,

    Yes, because the internal boot changer MOSFET is disabled on your condition. So at light load, the output needs to be ~2V lower than SW than boot capacitor can be charged again. You can refer to the application note:

  • 0 in reply to Iven Su
    Genius 3945 points

    Hello.

    thank you for your answer.

    We are looking at the application notes.
    We have questions.

    ①　About　Fig19.BOOT-SW UVLO vs Junction Temperature
    The data is posted as BOOT-SW UVLO on the data sheet of TPS54560B.
    How much does it vary from device to device?
    Do you have variation data?

    ② Boot-SW capacitor
    What is the maximum capacity?
    Is there a problem with a large capacity?


    Results confirmed on actual machine: No problem with capacity of 10uF or less.
    In case of 22uF or more. At startup: When the voltage between the BOOT and SW rises, the output voltage has become stepped.

    Hope: I want to keep the voltage as long as possible when stopping. I want to increase the capacity.

    I'm considering using 10uF. Is there any problem?

    thank you.

  • 0 in reply to Masazumi Ishii
    TI__Mastermind 35190 points

    ①　About　Fig19.BOOT-SW UVLO vs Junction Temperature
    The data is posted as BOOT-SW UVLO on the data sheet of TPS54560B.
    How much does it vary from device to device?
    Do you have variation data?

    We only have typical data (figure 19). If recommended CBOOT cap is used (0.1uF) no issues will be had with hitting boot uvlo.

    ② Boot-SW capacitor
    What is the maximum capacity?
    Is there a problem with a large capacity?

    We dont specifiy maximum capacity. Please use recommended CBOOt cap (0.1uf) for appropriate device operation. With large capacity cap, you can run into issue with correct device operation (failure for HS FET to turn on = failure for the device to regulate)

    Hopefully this information is helpful.

    Please let us know if we can help further.