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TMS320F280049: How to accurately monitor junction temperature (in system level)

Sheldon He
Expert 8585 points
Part Number: TMS320F280049


Hi expert,

My customer has an application in which F280049 is inside a rotation machine. In this case, F280049 works in high ambient temperature so they need a functionality to monitor temperature (ambient or junction) to protect F280049 when temperature is too high (in some fault state temperature will rise).

We noticed that internal temperature sensor has a typical accuracy of +- 15 degrees centigrade which will not do a precise protection.

Could we put a surface mount NTC/PTC on PCB board to monitor ambient temperature and indirectly project the MCU? If we could, how?

Thanks

Sheldon

  • 0
    TI__Guru 60865 points
    Hi Sheldon,

    You've got a couple options.

    The internal temperature sensor reading is actually quite precise, just not accurate. If the assembled system is (or can be) subject to testing at max temperature, you can capture a raw sensor reading at that time and use that to determine your temperature alarm limit.

    Otherwise, yes, you'll want an external temperature sensor. Assuming the PCB with the F28004x will see generally uniform temperature, the ambient reading from the external sensor should be a reasonable alarm.

    If you intend to trigger the alarm very close to the max F2837x junction temperature, you may want to factor in the junction to package temperature delta via the equations in the datasheet in "5.7 Thermal Resistance Characteristics".

    For these equations, you'll need the device power dissipation. You can use (in increasing order of accuracy) the max or typical value from the datasheet currents tables, a measure you take in development of the F28004x currents while the application is executing, or you can use spare ADC channels + a current shunt resistor + op amp to do a real-time measurement of the device currents.