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LM4952: Thermal Shutdown

ttd
Mastermind 8570 points
Part Number: LM4952

Tool/software:

Dear Technical Support Team,

The LM4952 has a thermal shutdown function,
What is the internal circuitry of the LM4952?

For example, is there a temperature monitoring circuit built in near the output buffer circuit on the DIE?

Best Regards,

ttd

  • 0
    TI__Genius 17530 points

    Hello,

    Yes you are correct LM4952 has thermal shutdown feature where the device internally monitors the temperature. I can't comment on the exact internal circuitry but when the device reaches 170 C the feature will be enabled and the device will shutdown. 

    Regards,
    Sydney Northcutt

  • 0 in reply to Sydney Northcutt
    Mastermind 8570 points

    Hi Sydney Northcutt,

    Thank you for your reply.

    What is the specific junction temperature when the thermal shutdown is 170°C?

    Is there a graph showing the relationship between the change in temperature monitored by thermal shutdown and
    the junction temperature?

    Is there a graph showing the relationship between junction temperature and case temperature?

    Best Regards,

    ttd

  • 0 in reply to ttd
    TI__Genius 17530 points

    Hello,

    I am looking into your inquiry. Please expect a response tomorrow. 

    Regards,
    Sydney Northcutt

  • 0 in reply to Sydney Northcutt
    TI__Genius 17530 points

    Hello,

    ttd said:
    What is the specific junction temperature when the thermal shutdown is 170°C?

    When thermal shutdown is enabled the junction temperature reached 170 C. 

    ttd said:
    Is there a graph showing the relationship between the change in temperature monitored by thermal shutdown and
    the junction temperature?

    The junction temperature is what monitors the temperature to enable thermal shutdown. If thermal shutdown is enabled it is because the junction reached 170 C.

    ttd said:
    Is there a graph showing the relationship between junction temperature and case temperature?

    We do not have a graph but we have the thermal resistance deltas. The junction to case delta is 4 C / W so for one 1 W output the difference between the junction and the case will be 4 C. You can use the below formula to ensure the output power (with efficiency considered) does not go above the junction temperature max. 

    Regards,
    Sydney Northcutt

  • 0 in reply to Sydney Northcutt
    Mastermind 8570 points

    Hi Sydney Northcutt,

    Thank you for your reply.

    I'd like to confirm that the junction temperature for  Absoblute Max Ratings  on datasheet shows 150℃. Is it correct?

    Thermal shutdown temp is 170℃ and so it beyods the 150℃. 

    Best Regards,

    ttd

  • 0 in reply to ttd
    TI__Genius 17530 points

    Hello,

    Yes this is correct. The junction max temperature is 150 C and should be used as the max value to set your design around. The thermal shutdown feature that is triggered at 170 C is utilized in unforeseen use cases to keep the junction temperature from increasing further and damaging the device.

    Regards,
    Sydney Northcutt