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LM4950 Thermal Shutdown and Short protection

Kuramochi Tadahiko
Guru 28715 points
Other Parts Discussed in Thread: LM4950

Hi,

I received following questions from my customer about thermal shutdown and short protection.

I couldn't find the their detail.

1. Where is detecting point of thermal shutdown ?

   e.g.) Output stage of power amplifier

2. What is the return condition from thermal shutdown?

    Is it decreasing temperature or shutdown by power supply?

    How many degrees is it if return condition is decreasing temperature?

3. How does LM4950 detect short condition?

    Does it measure output current?

4. What is the return condition from short protection?

    Is it decreasing current or shutdown by power supply?

Please confirm them.

Best Regards,

Kuramochi

 

 

  • 0
    TI__Mastermind 20085 points
    Hi Tadahiko-san

    1) The thermal shutdown turns the device off when junction temperature surpasses 150 °C.
    2) When the temperature decreases some degrees (I don't know exactly how many degrees) the device starts to work normally.

    Unfortunately, I don't have access to any detailed information on how short circuit protection works on this part and there isn't EVM available to perform these tests.
    But based on my experience in class AB devices.
    3) The class AB amplifiers usually have a kind of current limiter for short-circuit protection. If the output current level exceeds the threshold current, the device activates the short-circuit protection.
    4) After of a short-circuit condition, the output current decreases until that it is lower than threshold current, and the device will start to work normally.

    Best Regards
    Jose Luis Figueroa
    Audio Applications Engineer | A-Team
  • 0 in reply to José Luis
    Guru 28715 points
    Luis-san,

    Thank you for your support.

    >2) When the temperature decreases some degrees the device starts to work normally.
    Is this operating certain?
    I would like to answer for my customer for sure.
    Regards,
    Kuramochi
  • 0 in reply to Kuramochi Tadahiko
    TI__Mastermind 20085 points
    Tadahiko-San

    For instance, the device is working normally, but after a few minutes the junction temperature surpasses 150 °C, then the thermal shutdown turns the device off, until that the junction temperature decreases some degrees, the device starts to work normally again.
    Please let me know if you have more questions.

    Best Regards
    Jose Luis Figueroa
    Audio Applications Engineer | A-Team