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DRV8316: FB_BK and SW_BK pin connection when buck converter is not used

Conor
Guru 12235 points
Part Number: DRV8316

Hi,

Please tell me the recommended processing method for the FB_BK pin and SW_BK when the buck regulator is not used.

The data sheet has the following image, but it seems that there is no description about the recommended processing method when the buck regulator is not used.

Thanks,

Koki

  • 0
    TI__Mastermind 21805 points

    Hello Koki-san,

    As the note recommends, external components for the regulator MUST BE POPULATED. The DRV8316 powers up with the regulator enabled and will not start up properly if these components are not in place.

    Thanks,

    Matt

  • 0 in reply to Matt Hein
    Guru 12235 points

    Hi, Matt

    Thank you for your reply!

    Matt Hein said:
    external components for the regulator MUST BE POPULATED.


    →OK, Even if I don't use a buck regulator, I still need to connect the components (LBK, RBK and CBK), right ?

    　(1)What are the recommended values for LBK, RBK and CBK when the buck regulator is not used?

    　(2)Also, please tell me the connection destinations of FB_BK, SW_BK and GND_BK when I do not use the back regulator.

    Thanks,

    Koki

  • 0 in reply to Conor
    TI__Mastermind 26046 points

    Hi Koki-san,

    1) Please use LBK = 22uH or 47uH, RBK = 22 ohm, CBK = 22uF. Buck or resistor can be used for LBK/RBK when buck is not used. We have seen customers use a 22 ohm resistor for LBK/RBK when the buck regulator isn't used.

    2) GND_BK can be tied to the DRV8316's thermal pad GND, SW_BK routes from the pin to LBK, and FB_BK routes from buck output back to FB_BK pin. See below. 

    Thanks,
    Aaron

  • 0 in reply to Aaron Barrera
    Guru 12235 points

    Hi,

    At present, assuming that the built-in Buck converter is performing PWM control by voltage feedback, it is designed by processing as follows in order to reduce the number of parts, and no abnormal operation is observed. 

    ・ Connect FB_BK to an external 3.3V that boots before the VM
    ・ SW_BK is open
    ・ GND_BK is connected to PGND

    Can the above pin handling method be a problem? If so, what are specific concerns?

    Thanks,

    Koki

  • 0 in reply to Conor
    TI__Mastermind 26046 points

    Hi Koki-san,

    I am chatting with systems about SW_BK left floating and getting a recommendation about smallest BOM for leaving the buck unused in the DRV8316. 

    I know it is okay to connect FB_BK to external 3.3V that boots before VM. TI recommends connecting GND_BK to AGND rather than PGND becuase TI recommends connecting the thermal pad GND to AGND (rather than PGND) for best thermal dissipation. 

    Thanks,
    Aaron

  • 0 in reply to Aaron Barrera
    TI__Mastermind 21805 points

    Hello Koki-san,

    Do you need any further assistance on this thread?

    Thanks,

    Matt

  • 0 in reply to Matt Hein
    TI__Mastermind 21805 points

    Hello Koki-san,

    I'll close this thread, but if you have further comments please click the "Ask a related question" button!

    Thanks,

    Matt