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MCT8316A: About Buck/LDO Regulator

Tachibana Masanori
Prodigy 100 points
Part Number: MCT8316A

Hello support teams,

We have some questions about Buck/LDO Regulator of MCT8316A.
We will use it in resistor mode. (RBK = 22 ohm, CBK = 22 µF)

Questions:
1. Does CBK value which is greater than the recommended value of 22µF cause any problems?
We would like to use two or more 22µF in parallel for CBK, considering the DC bias characteristics of ceramic capacitors.

2. Does it work as LDO regulator when used in resistance mode?
How is the regulator detected and switched the operation of the Buck mode and LDO mode?

Best regards,
M. Tachibana

  • 0
    TI__Mastermind 26516 points

    Hi Masanori-san,

    Thanks for your question!

    I am checking with some coworkers on these questions and will try to provide a response in the next couple days.

    Regards,

    Anthony Lodi

  • 0 in reply to Anthony Lodi
    TI__Mastermind 26516 points

    Hi Masanori-san,

    I need a little more time to provide a response to your questions, I will try to get them answered by early next week.

    Sorry for the delay,

    Anthony Lodi

  • +1
    TI__Mastermind 26516 points

    Hi Masanori-san,

    Thank you for your patience!

    1. If a larger CBK value is used, then this will likely result in the buck powering up slower on the power on of the device. This is the main drawback that I am aware of with having a larger CBK value. In order to help reduce the issue of capacitance derating that arises from operating ceramic capacitors close to their rated voltage, we recommend using capacitors with a voltage rating that is at least 1.5x to 2x greater than the voltage that the capacitor will see. 

    2. The buck doesn't switch over to an LDO regulator in resistance mode. Whether the buck is in inductor mode or in resistor mode, the buck regulates the voltage based on the feedback Vref voltage that is measured by the buck; from the perspective of the buck it doesn't care whether a resistor or inductor is connected. 

    Regards,

    Anthony Lodi

  • +1 in reply to Anthony Lodi
    Prodigy 100 points

    Hi Anthony-san,

    Sorry for my late response due to our long holiday.
    I appreciate your advice, and I understood it.

    I will determine the value of CBK in consideration of the rated voltage and the DC bias characteristics of the capacitor .

    Thanks and best regards,
    M. Tachibana

  • 0 in reply to Tachibana Masanori
    TI__Mastermind 26516 points

    Hi Masanori-san,

    Glad I could help out!

    Regards,

    Anthony Lodi