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TPS25750: current flows from VIN_3V3 pin for a short time as the dead-battery start-up condition

Shinya Honda
Prodigy 30 points
Part Number: TPS25750

We mount the TPS25750 on our controller unit and we can connect the tablet with it.
The controller unit works as source only.

When the controller unit is powered off, the tablet temporarily supplies power from VBUS, and the TPS25750 operates as a dead battery condition.

At this time, no current should flow from the VIN_3V3 pin, but we observed the current from VIN_3V3 for a short time.
This current raises the voltage on VIN_3V3 to approximately 0.15V.

The voltage may rise more, causing the controller unit to repeatedly turn on and off. We are worried about damaging the device in the unit, and have some questions.

  • Is there any specification on the current flowing from the VIN_3V3 pin and the time until the current stops?
    Unless otherwise specified, it may be necessary to pull down the VIN_3V3 pin voltage to prevent it from rising, or to use a protection device to prevent reverse voltage from being applied to the device.
  • What configuration suppresses the current flowing from the VIN_3V3 pin? EEPROM and pin strapping.

Regards,

  • 0
    TI__Mastermind 22165 points

    Hi Shinya,

    What is the capacitance on the VIN_3V3 line? The nominal capacitance is 10uF and while there is no max, too high of a capacitance can cause a longer time period for voltage to drop. 

    Thanks and Regards,

    Raymond Lin

  • 0 in reply to Raymond Lin
    Prodigy 30 points

    Abount 15uF on the VIN_3V3 line on the circuit schematic, while actually 10uF, dc bias taken into consideration.

    We are worried reverse voltage causing the damage to regulator device, VIN_3V3 pulled up while 5V power line staying at 0V.

    Regards,

  • 0 in reply to Shinya Honda
    TI__Mastermind 22165 points

    Hi Shinya,

    The TPS25750 has built-in RCP/RVP on it's pin which should protect it for simple cases (less than 5V). 

    This small amount of voltage shouldn't be an issue, however I would recommend to review your schematic to see if there's any parasitic capacitance or improper drainage on the VIN_3V3 line.

    Thanks and Regards,

    Raymond Lin