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TPS65917-Q1: Power-on Acknowledge

Hayashi
Expert 1840 points
Part Number: TPS65917-Q1

Hi teams

I have questions about power-on acknowledge by TPS65917.

Please let me know about the follows?

I. What does the function about power-on acknowledge?

I don't understand how be affected this function.
Is it necessary when the device is turned on?

II.When does It use the powerhold function?

The autodevon function can be set to poweron according to instructions from the MCU.
But the powerhold pin has a hard pin and I do not know who should turn it on / off at what timing.

If this function don't use, is it problem to connect to High always?

Best regards

Hayashi

  • 0
    TI__Expert 8730 points
    Hi,

    I have assigned your request to responsible Applications Engineer and we will get back to you as soon as possible.

    Regards,

    Murthy
  • 0
    TI__Genius 16410 points
    Hello Hayashi,

    > I. What does the function about power-on acknowledge?
    Power-on acknowledge is a way for the system to tell the PMIC that it is powered up correctly when using PWRON to enable the PMIC. When PWRON goes low, the PMIC will only stay on for 8 seconds before it shuts off, unless there is a "power-on acknowledge" event. This power-on acknowledge event is setting DEV_ON bit to 1, or setting POWERHOLD high.

    If AUTODEVON is set, then the DEV_ON bit is automatically set to 1, and the PMIC will not shut off after 8 seconds.

    > II.When does It use the powerhold function?
    If you want to use POWERHOLD to enable/disable the PMIC, then you don't need to worry about power-on acknowledge. The PMIC will be enabled as long as POWERHOLD Is high. This means setting POWERHOLD high will enable the PMIC, and setting POWERHOLD low will disable the PMIC. Typically in the application, a microcontroller will set the POWERHOLD pin when it wants to enable or disable the PMIC.

    Setting POWERHOLD always high is ok if you want the PMIC to be always on. In this case, you could also control RESET_IN to enable or disable the PMIC, since both RESET_IN and POWERHOLD need to be high for the PMIC to be enabled.

    Please let me know if you have any more questions about this.

    Regards,
    Karl
  • 0 in reply to Karl Wallinger
    Expert 1840 points
    Karl san

    Thank you for your reply.
    I'm catching on.
    I still have a questions.Please let me know to tell?

    > I. What does the function about power-on acknowledge?
    Does the event of power-on acknowledge must come into that state when it power on?

    I cannot still understand that how does this event of power-on acknowledge happen.
    Does it happen only after event of OFF2ACT or SLP2ACT?
    And, is this able to come the powerhold mode and the AUTODEVON mode same time or which is dominant?

    > II.When does It use the powerhold function?
    What is this the function assuming the situation?

    Best regards
    Hayashi
  • 0 in reply to Hayashi
    TI__Genius 16410 points

    Hello Hayashi-san,

    Let me try to explain the whole power enable function, I hope this can answer your questions.

    The PMIC needs an ON request to turn on the PMIC.  This is either PWRON=low, or POWERHOLD=high.  The PMIC enable is an OR function of these, so either PWRON=low or POWERHOLD=high will enable the PMIC.

    After enabled, the PMIC also needs a power-on acknowledge to stay on after the OFF2ACT sequence.  This is either DEV_ON=1, or POWERHOLD=high.  This is also an OR function, so either DEV_ON=1 or POWERHOLD=1 will keep the PMIC on.

    Together, these create 4 common use cases to enable the PMIC:

    1. AUTODEVON mode
      In this mode, PWRON is used to enable the PMIC, and DEV_ON is automatically set by the PMIC to keep the PMIC on.  In this case, the PMIC will be enabled until a processor writes DEV_ON=0.  Note that AUTODEVON is only set by OTP, and cannot be set by I2C.
    2. DEV_ON mode
      In this mode, PWRON is used to enable the PMIC, and needs DEV_ON=1 to keep the PMIC on.  Once the processor is powered, it should send an I2C command to the PMIC to set DEV_ON=1.  If it does not, the PMIC will shut off after 8 seconds.  Once DEV_ON=1, the PMIC will be enabled until the processor writes DEV_ON=0.
    3. PWRON / POWERHOLD mode
      In this configuration, PWRON is used to enable the PMIC, and needs POWERHOLD=high to keep the PMIC on.  Once the processor is powered, it should enable a GPIO connected to POWERHOLD, so that it sets POWERHOLD=high.  If it does not, the PMIC will shut off after 8 seconds.  Once POWERHOLD=high, the PMIC will be enabled until POWERHOLD=low.
    4. POWERHOLD-only mode
      In this configuration, POWERHOLD is used to enable the PMIC.  Since POWERHOLD is both an ON request and power-on acknowledge, the PMIC will stay on as long as POWERHOLD is high.  So when using POWERHOLD to turn on the PMIC, the PMIC will be enabled until POWERHOLD is set low.

    There is no configuration or selection of these 4 modes.  The PMIC will always be enabled by either PWRON or POWERHOLD, and will always stay enabled if DEV_ON=1 or POWERHOLD=high.  You just choose whichever use case makes the most sense for your system.

    Does this answer your questions?  Please let me know if you have any further questions.

    Regards,
    Karl