This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LP2989: Output voltage fall to 1V instead of 3.3V

Part Number: LP2989

Hello,

I have a LP2989AILD-3.3 on a board (WSON package), and the component output fall to 1V when the ambient temperature up to 70°C.

The output can stay to 1V for hours with a temperature of 25°C and return to 3.3V.

The input voltage is 5V, and there is 10uF ceramic capacitors at the output and input. (10nF bypass capacitor)

The output current is 25mA, and the junction temperature of the component must be "ambient + 1.5°C".

We product severals boards but only one have the default.

Have you already see this type of default ?

Best regards,

  • Hi Florian,

    In order to help debug, could you provide a scope shot with Vin, Vout, and Iout?

    Very Respectfully,
    Ryan
  • Hi Ryan,

    I can't measure output current easily, but i tried to inject an external power supply 3.3V with a serie resistor (1.5 ohm) and i saw 2.5mA (constant).

    You can see the establishment of input and output with low load.

    And with a 120ohms resistor at the output :

    We can see that the output is 1V with low load (2mA normally with 3.3V), and 50mV with 120ohms load (27.5mA normally with 3.3V).

    Thank you,

    Florian

  • Hi Florian,

    Thank you for the scope shots.  Since the output voltage comes up to a different voltage depending on the load, we should look for an unintentional bias such as excessive flux that was not removed from the board that could be biasing the output voltage low.  In particular, please look around the SENSE and BYPASS pins as an unintentional bias current on either of these pins will impact the output voltage.

    Very Respectfully,

    Ryan