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MSP430FR5849: Operation at high temperatures

Michael Carsten
Prodigy 10 points

Part Number: MSP430FR5849

I am seeking clarification on the temperature limits and out-of-range behavior of the MSP430FR5849IRHAT.

What behavior should we expect if the device temperature exceeds 85°C? Specifically, does the device reset, enter brownout, experience degraded operation, or exhibit some other defined behavior? Are there any protections or temperature-monitoring mechanisms that would act before or at this condition?

Additionally, the datasheet lists both the operating free-air temperature range and operating junction temperature range as -40°C to 85°C. Is this correct, or should the junction-temperature limit differ from the free-air/ambient operating-temperature li8d7ebf57-3207-4d9a-b667-b7fe69621e2c.jpgmit?

  • 0
    TI__Expert 8275 points

    Hi Michael,

    Yes, the values in the datasheet are correct for the MSP430FR5849IRHAT. Both the operating free-air temperature, TA, and operating junction temperature, TJ, are specified as -40°C to 85°C in the Recommended Operating Conditions.

    The 85°C limit is not a thermal trip point. The device does not automatically reset, enter brownout or shut down when its temperature crosses 85°C. The brownout and supply-voltage supervisor circuits monitor supply voltage, not temperature.

    Operation above 85°C is outside the characterized and guaranteed operating range. The device may continue to run, but its behavior and electrical specifications are no longer guaranteed. Parameters such as leakage current, clock behavior, ADC/reference accuracy, timing and memory reliability may change. Therefore, the application should not depend on a predictable failure mode or reset occurring above 85°C.

    The -40°C to 125°C storage-temperature rating in the Absolute Maximum Ratings applies to storage and does not permit powered operation up to 125°C.

    The device does include an internal temperature-sensor channel that can be measured using the ADC12_B. However, it is only a measurement function; it does not initiate an automatic reset or shutdown. Firmware can periodically read the sensor and take action, such as reducing activity, entering a low-power mode or generating a system fault. The uncalibrated sensor offset may be as high as ±30°C, so the factory calibration values stored for 30°C and 85°C should be used, along with an appropriate safety margin. See Table 5-30.

    TA and TJ are separate quantities even though their specified limits are the same:

    TJ ≈ TA + (power dissipation × θJA)

    For the RHA package, the datasheet lists a nominal θJA of 30.1°C/W under the stated JEDEC test conditions. The actual temperature rise depends on the PCB, airflow, operating current and external heat sources. Therefore, when the ambient temperature approaches 85°C, sufficient margin is needed to keep the junction temperature at or below 85°C.

    If operation above 85°C is a system requirement, a device explicitly rated for the required temperature range should be selected. Application testing cannot extend the guaranteed rating of the MSP430FR5849IRHAT.

    Hope this helps!

    -Brian

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