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TPS65911: For the pin of VBACKUP(D7) power connection

user4919763
Prodigy 30 points
Part Number: TPS65911

Hi,

For TPS65911's VBACKUP pin, both +V3.3_SB and +V3.3_RTC power are connected to it , please refer below picture.

Is there special requirement for this pin? Should I only use +V3.3_SB connect to it without +V3.3_RTC(eg. remove R692)? Is there any side effect for PMIC after I remove R692?

ps, +V3.3V_SB is always on when power adpator plug in, but when power adaptor is removed, there will be only +V3.3V_RTC on my board.

Thanks.

  • 0
    TI__Mastermind 30310 points
    Thank you for posting your question on the TPS65911 device in the e2e forum. This question is very specific to the device in question and is outside my area of expertise. I have assigned this question to the expert on this device.
  • 0
    TI__Mastermind 30310 points

    Is the rail named "+V3.3_RTC" connected to the B5 pin (VRTC) of the TPS65911?

    Do you have a physical battery connected to the "+V3.3_BAT" rail in your design? If you have a backup battery, this is the only thing that should be connected to the D7 pin of the TPS65911.

    The VRTC rail of the TPS65911 (pin B5) is a power output that can receive power from VCC7 or VBACKUP.

    My understanding is that neither "+V3.3_RTC" nor "+V3.3_SB" should be connected to the VBACKUP input (pin D7) on the TPS65911. Only a backup battery should be connected here. Your schematic looks like VRTC is wired to itself through R692, which would not be a good idea.

    The TPS65911 expert assigned to this thread can confirm my interpretation.

  • 0 in reply to Brian Berner
    TI__Genius 16410 points
    Hello,

    It depends on whether or not you want RTC functionality in backup mode. The function of VBACKUP is to supply the RTC module in the PMIC while the main battery is off. If you want to use the RTC, I think you should use +V3.3_RTC supply, since you say this will still be supplied when the power adapter is removed.

    If you don't need RTC functionality when the main battery is off, then either supply is ok to use. If VBACKUP is unpowered while the main VCC7 supply is off, then the PMIC will lose all the RTC and time status.

    Regards,
    Karl
  • 0 in reply to Karl Wallinger
    Prodigy 30 points

    Understand,thanks Karl.