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Original question:

DRV8316: Regarding SPI_FLT_REP setting

DRV8316: Regarding power sequencing

Daisuke Higa
Genius 3785 points
Part Number: DRV8316

Hi support team.

My customer asked me regarding power sequence configured by BUCK_PS_DIS.
We found the comment in datasheet below.

-------------------------------------------------- -------------------------------------------------- --------------------------
This sequencing can be configured through the BUCK_PS_DIS bit.
Power sequencing is supported only when buck output voltage is set to 5.0 V or 5.7 V.
-------------------------------------------------- -------------------------------------------------- -------------------------------------------------- -------------------------------------------------- --------

Q:

The default setting for BUCK _PS_DIS bit is 0h, therefor initial position of the switch is connected Vbk.
And The default setting for BUCK_SEL bit is 00h, therefor The voltage of FB_BK is 3.3V.
Immediately after the DRV8316 is started, the AVDD voltage is set to 3.3V, so the input and output of the A VDD circuit are the same voltage.

Is this condition inconsistent with the above described in the data sheet?

Do I have to set the BUCK _SEL bit to 01h or 11h after startup?

Best Regards,

Higa

  • 0
    TI__Mastermind 18916 points

    Hi Higa-san, 

    Our team will look into this and aim to give you a response soon by early next week 

    Best Regards, 
    Andrew 

  • 0 in reply to Andrew Liu
    TI__Mastermind 26046 points

    Hi Higa-san,

    I understand your question. By default the buck is powering AVDD, and BUCK_SEL = 3.3V, so if this is the default, then this should not be supported because the datasheet also specifies that "Power sequencing is supported only when buck output voltage is set to 5.0 V or 5.7 V".

    I need to check with the systems the validity of "Power sequencing is supported only when buck output voltage is set to 5.0 V or 5.7 V".

    A good way to test this in parallel is to operate a motor and measure the IC temperature in these 3 conditions:

    1) BUCK_PS_DIS = 0b and BUCK_SEL = 3.3V (Default condition, power sequencing should not be working in this condition, IC temp should be higher)
    2) BUCK_PS_DIS = 0b and BUCK_SEL = 5.7V (Power sequencing should be working, IC temp should be lower)
    3) BUCK_PS_DIS = 1b and BUCK_SEL = 5.7V (Power sequencing should be disabled, IC temp should be higher)

    I can do some testing on this by the end of the week to confirm if PS is not enabled at default conditions on powerup. 

    Daisuke Higa said:
    Do I have to set the BUCK _SEL bit to 01h or 11h after startup?

    If the conditions above hold true, then yes, BUCK_SEL should be set to those settings at powerup. 

    Thanks,
    Aaron

  • 0 in reply to Aaron Barrera
    Genius 3785 points

    Hi Aaron-san

    Thank you for answering.

    We consider it to be the case 1) presented.
    The default setting is BUCK_PS_DIS = 0b, but the power sequence function does not work, and the power path at startup may be that the VM and A VDD are connected.
    Is this correct?

    Best Regards,

    Higa

  • 0 in reply to Daisuke Higa
    TI__Mastermind 26046 points

    HI Higa-san,

    Daisuke Higa said:
    The default setting is BUCK_PS_DIS = 0b, but the power sequence function does not work, and the power path at startup may be that the VM and A VDD are connected.

    I am checking with the systems engineer and on the EVM, please allow me to have a reply by end of the week.

    Thanks,
    Aaron

  • 0 in reply to Aaron Barrera
    Genius 3785 points

    Hi Aaron-san

    Do you have any update?

    Best Regards,

    Higa

  • 0 in reply to Daisuke Higa
    TI__Mastermind 26046 points

    Hi Higa-san,

    I am still waiting for an update, I have reached out to the systems engineer again. 

    Thanks,
    Aaron

  • 0 in reply to Aaron Barrera
    TI__Mastermind 26046 points

    Hi Higa-san,

    Daisuke Higa said:
    Do I have to set the BUCK _SEL bit to 01h or 11h after startup?

    Yes, you have to do this after startup. 

    Is the customer okay with this?

    Thanks,
    Aaron

  • 0 in reply to Aaron Barrera
    Genius 3785 points

    Hi Aaron-san

    Excuse me. I'm not sure.
    Let me check again.
    My customer does not use a buck regulator.

    -Which is the switch position set by BUCK_PIS_DS at startup? (Which is connected to VM or VBK?)

    If it is a VM, why is the initial setting BUCK_PIS_DS bit = 0 (connected to VBK)?

    -Is it necessary to change the BUCK_SEL setting after startup even if the buck regulator is not used?

    Best regards,

    Higa

  • 0 in reply to Daisuke Higa
    TI__Mastermind 18916 points

    Hi Higa-san, 

    Our team is currently out of office today for July 4th holiday in the US - but we will review your question and aim to provide a response by end of the week. Thanks!

    Best Regards, 
    Andrew 

  • 0 in reply to Andrew Liu
    TI__Mastermind 26046 points

    Hi Higa-san,

    DRV8316 starts by default on VM during power up and based on the SPI setting, it selects VM or VBK. In this case it will stay on VM till buck output is configured >4V. BUCK_PS_DIS = 0b at startup has no effect until BUCK_SEL > 4.0V. 

    Thanks,
    Aaron

  • 0 in reply to Aaron Barrera
    Genius 3785 points

    Hi Aaron-san

    Thank you for confirming and support.

    I understand.

    However, I had another question.
    The content will change, so I will post a new one.

    Best regards,

    Higa