• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 29 subscribers
  • Views 309 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

MCT8316A: BUCK regulator disabling/not using.

ArTzy
Mastermind 18710 points
Part Number: MCT8316A


Hi Experts,

Can you help the query below from customer about MCT8316A1VRGFR design? Posting it on this behalf:

I have external 5V and 3.3V sources in my design and no need to use MCT8316A internal Buck.
Can I totally disable MCT8316A Buck regulator and not populate nor inductor, nor resistor, nor capacitor.
See fig. 8-3, 8-4 in MCT8316A datasheet.

How SW_BK and FB_BK should be connected? Float?
Any additional settings must be used for MCT8316A EEPROM?

Any pros. and cons. for using (not using) Buck? 

As I understand with buck disabled there are more current consumption and I can not use AVDD Power Sequencing from Buck Regulator.
See fig. 8-5.

Thank you for your usual support.

Regards,
Archie A.

  • +1
    TI__Expert 5578 points

    Hi Archie,

    Thanks for your question on the Motor Drives E2E Forum.

    When using the MCT8316A, the customer must populate the external components around the buck even if they are not using the buck output. This includes SW_BK, GND_BK, and FB_BK. The feedback from the buck is also used to power some of the internal circuitry in the device so depending on customer key spec requirements, they can either populate the Buck in resistor or inductor mode. 

    Populating the Buck in Resistor mode will allow the customer to save board space and save on costs, but they may lose some efficiency that is offered by the buck in inductor mode. There will be more losses when populated in resistor mode, so customer should keep that consideration in mind when choosing which mode to populate with the external buck components.

    Best,

    Robert

  • 0 in reply to Robert Wedan
    TI__Mastermind 18710 points

    Thanks for this detailed guidance, Robert.

    Would like to clarify:

    Robert Wedan said:
    There will be more losses when populated in resistor mode, so customer should keep that consideration in mind when choosing which mode to populate with the external buck components.
    You talk about resistor vs inductor losses or MCT Buck "internal" losses?
    (Higher MCT8316A case temperature in "resistor mode")
    Thank you.
    Regards,
    Archie A.
  • +1 in reply to ArTzy
    TI__Expert 5578 points

    Hi Archie,

    I was talking about the resistor vs inductor losses. When in inductor mode, the buck regulator output will see a higher efficiency. 

    Even when not used, this output is fed back into the motor driver through FB_BK and used to power some other internal circuitry. Knowing this, we can deduce that the motor driver itself will see a higher power efficiency in inductor mode when compared to resistor mode. 

    However, in resistor mode, customer may save board space and cost by populating with a resistor instead of an inductor. 

    Let me know if this answers your question more accurately.

    Best,

    Robert