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About TPS259261

watanabe
Expert 1740 points

Hi,

My customer has some question.

Q1.
When VIN is in the state of off , EN/UVLO pulled high to 3.3V,
EN / UVLO will be 1.7V.
When VIN is in the state of on , EN/UVLO pulled high to 3.3V,
EN / UVLO will be 3.3V.

What is the cause of this phenomenon?


Q2.
Looking at the 7.1 Absolute Maximum Ratings ,rating of datasheet of EN/UVLO is 7V.
Looking at the 9.2 Typical Application, it looks okay to pulled high to 18V in 1Mohm.

What is the inside of the EN / UVLO pin?

Best regards,

Kenta Watanabe

  • 0
    TI__Guru** 105811 points
    Hi Watanabe,

    Ans for Q1:
    When EN/UVLO pulled high to 3.3V with VIN in state of OFF, you can expect 1.7V typ at VIN pin but this voltage level should not cause any problem as it is less than VIN minimum (4.5V).
    Resistor + diode network is placed between VIN and EN/UVLO pins to facilitate internal pullup.
    Does this scenario raise any concern in your application?

    Ans for Q2:
    The EN/UVLO pin has an internal low voltage clamp, which can sink up to 20uA current. The 1Mohm limits the current to EN/UVLO pin to <20uA.

    Best Regards,
    Rakesh
  • 0 in reply to Rakesh
    Expert 1740 points
    Hi Rakesh,

    Thank you for your quick reply.
    I understood Ans for Q2.

    I have a question for Ans for Q1.

    VIN is off, and the 10kohm pull up the EN/UVLO to 3.3V,
    EN/UVLO will fall to 1.7V, why?
    (When the VIN rises, EN rises up to 3.3V)

    Is there a problem EN / UVLO pulled high to 3.3V with VIN = 0V?

    Best Regards,
    Watanabe
  • 0 in reply to watanabe
    TI__Guru** 105811 points
    Hi Watanabe,

    As mentioned above, there is resistor + diode network between VIN and EN/UVLO pins.
    When Vin=0 and EN/UVLO pin is pulled high to 3.3V through 10kohm, the external 10kohm resistor and internal resistor + diode network forms a circuit which results in 1.7V at EN/UVLO pin.
    This should not cause any problem from the device operation perspective.

    Best Regards,
    Rakesh
  • 0 in reply to Rakesh
    Expert 1740 points
    Hi Rakesh,

    I appriciate for your support.
    I understood the mentioned above.
    Thank you again.

    Best Regards,
    Watanabe
  • 0 in reply to watanabe
    TI__Guru** 105811 points
    Hi Watanabe,
    Thank you!
    Keep posting your queries
    Have a nice day

    Regards,
    Rakesh