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Over-current protection of TPS25921L

Takahiro Nishizawa
Genius 5575 points
Other Parts Discussed in Thread: TPS25921L

We have questions about TPS25921L.

Question 1.

Please tell us the time it takes from the current reaching the threshold of ILIM to shutdown.

Question 2.

Please tell us the accuracy of over-current detection.

What is the variation of over-current detection between devices except external resistor.

Best regards,

Takahiro Nishizawa

  • 0
    TI__Guru 57737 points

    Hi Takahiro,

    During overload conditions, the internal current-limit amplifier regulates the output current to ILIMIT. The output voltage droops during current limit regulation, resulting in increased power dissipation in the device. If the device junction temperature reaches the thermal shutdown threshold (T(TSD)), the internal FET is turned off.

    The amount of Power dissipation is dependent on the Load Current and Output capacitance. Once you know the Power Dissipation across the FET, you can use the below graph to determine the time before Thermal Shutdown.

    The variation of Current limit threshold for different resistor settings across Temperature range and devices is mentioned in electrical characteristics table as shown below,

  • 0 in reply to Praveen GD
    Genius 5575 points
    Thank you for your answer!


    We have new question about T(fastrip) 3µS.

    Does 3µS mean the time from reaching threshold of Ifastrip to shutdown?
    or decreasing current only in 3µS?

    Best regards,
    Takahiro Nishizawa
  • 0 in reply to Takahiro Nishizawa
    TI__Guru 57737 points

    Hi Takahiro,

    As you can see from the image below, T(fastrip) is the time from reaching threshold of Ifastrip to shutdown.

  • 0 in reply to Praveen GD
    Genius 5575 points
    Thank you for your answer!

    Is these understanding correct?

    ILIM : The current exceeds the threshold of ILIM, the IC keeps current constant and decrease the voltage.
    But temperature rises when power dissipation increases.
    And temperature exceed the threshold of thermal shutdown. The IC shut down.

    Ifastrip : The current exceeds the threshold of Ifastrip,
    The IC shut down in 3µS.


    Best regards,
    Takahiro Nishizawa
  • 0 in reply to Takahiro Nishizawa
    TI__Guru 57737 points
    Hi Takahiro,

    You are correct!

    ILIM: When he current exceeds the threshold of ILIM, the IC keeps current constant and the output voltage decrease as the load current requirement is not met. This drop in output voltage increases the voltage developed across the FET. Now, there is Voltage across FET and Current flowing through it. This increases the Power dissipation in the FET.
    When the FET temperature exceeds the threshold of thermal shutdown, the IC shut down.

    Ifastrip : When the current exceeds the threshold of Ifastrip, the IC shut down in 3µS.
  • 0 in reply to Praveen GD
    TI__Guru 57737 points
    Hi Takahiro,

    Hope I have answered your questions. If you do not have more questions, can we close this thread?