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TPS25923: Output voltage in disabled

Gokhan Sahin
Prodigy 210 points
Part Number: TPS25923

Hi everyone,

I'm using your product in order to switch the power for Asus Tinker board.

Without Asus board, it works properly. However, when connected Asus board, there are around 1.5V at the output although IC (EN pin is 0V) is disabled.

Also, the power led of the board is keeping ON and lots of peripherals of it runs.

I'd like the output voltage to be 0V when it's disabled. 

(Note: There is a pull-down resistor is 100K at the output.)

  • 0
    TI__Guru 57737 points

    Hi Gokhan,

    It is surprising that there is output voltage of 1.5V when the device is disabled. Can you please check the following,

    • Please share your schematics for review
    • What is the voltage at BFET pin and at output when the part is disabled and board is not connected ? **Make sure that you measure BFET pin voltage with a High impedance (>10 Mohms) probe as the source current from this pin is very low (2 uA).
    • What is the voltage at BFET pin when the part is disabled and board is  connected ?
    • Is TPS25923 the only source of voltage to the board ? If not, what is the voltage at input of the board when TPS25923 is not connected ? This is to check if any other voltage source on your board is causing a leakage path.

  • 0 in reply to Praveen GD
    Prodigy 210 points

    • BFET pin isn't used in this project.
    • Yes, TPS25923 is the only source of voltage.
    • The schematic has been attached below.

  • 0 in reply to Gokhan Sahin
    TI__Guru 57737 points

    Hi Gokhan,

    You can still measure BFET even if you do not use it. BFET should be present when the part is enabled and Vin is above Vuvr.

    When part is disabled, volatge at BFET should be 0V. If there is voltage at BFET  when part is disabled, the IC is probably damaged.

    Is there any reason why you have high dvdt cap (100nF) ? What is the total output capacitance and load resistance during startup ?

  • 0 in reply to Praveen GD
    TI__Guru 57737 points

    Hi Gokhan,

    Can you please share your observations.

    If your issue is solved, can we close this thread ?

  • 0 in reply to Praveen GD
    TI__Guru 57737 points

    Hi Gokhan,

    Hope your issue is resolved. Please let us know if you have any other issue.