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Original question:

TPS25751: Proper device configuration for dead battery configuration and EEPROM requirements

TPS25751: Powering the TPS25751 Controller

William Fahrenkrog
Prodigy 20 points
Part Number: TPS25751


Tool/software:

I have a question related to using two TPS25751 controllers in a single design that has neither a battery nor battery charging capability.  A high-level block diagram is given below:

The intent for this design is to allow a user to connect a USBPD certified power supply into either port and have the secondary port be available for data and potentially sourcing power.  Prior to being powered up, both TPS25751 devices will be configured in dead battery mode.

Looking at the TPS25751 data sheet, figure 8-11 shows the following:

Since the TPS25751 controllers are starting in dead battery mode, initial power will come from VBUS and, then it will be up to the embedded controller to clear the dead battery flag.

Question 1: Is clearing the dead-battery flag equivalent to closing the RLDO_3V3 switch in figure 8-11 above?

Question 2: Once the system powers up through the first TPS25751 controller, there would be power coming in to VIN_3V3 and not VBUS.  However, if the dead battery flag is not cleared, does this prevent the TSP25751 controller from powering up?

Thank you,

William

  • +1
    TI__Mastermind 37655 points

    Hi William,

    William Fahrenkrog said:
    Question 1: Is clearing the dead-battery flag equivalent to closing the RLDO_3V3 switch in figure 8-11 above?

    Yes, you can think of it like this. The IC switches power from VBUS to VIN3V3. When the dead battery flag is set and we are in dead battery, we are limited to sinking from the port and will disable any sourcing behavior until the flag is cleared as well.

    William Fahrenkrog said:
    Question 2: Once the system powers up through the first TPS25751 controller, there would be power coming in to VIN_3V3 and not VBUS.  However, if the dead battery flag is not cleared, does this prevent the TSP25751 controller from powering up?

    No. There are two TPS25751 ics in this statement so let me break them apart.

    The TPS25751 that is sinking power and started in dead battery can still power up in dead battery conditions and will enter APP mode if a configuration is loaded properly (EEPROM or I2C Host), but as mentioned above, will have limited behavior (sink only, powered from VBUS).

    The other TPS25751 would be powered from the system and should boot with VIN3V3 first, so there should be no problems there.

    Thanks and Regards,

    Chris

  • 0 in reply to Christopher Lim1
    Prodigy 20 points

    Chris,

    Thank you for clear answer.  At this point I have no further related questions.

    -William

  • 0 in reply to William Fahrenkrog
    TI__Mastermind 37655 points

    Thanks,

    Closing this thread now. Please create a new thread if you have additional questions.

    Thanks and Regards,

    Chris