I have used TMS320F28377D microcontroller in a power controller board that requires safety compliance of criticality Level ‘A’ as per RTCA/DO-254. The internal temperature sensor of the microcontroller reads 55°C at power-on. At the end of a full load test (for 1 hr.) at room temperature, the junction temperature read 72°C.
The same code was loaded on evaluation board (no other device interfaced with the microcontroller) and noticed the same reading of 55°C at power-on (immediately after powering on the eval board and flashing the code) at room temperature.
The eval board was then kept inside a thermal chamber at 71°C temperature. After 10 mins of operation, the junction temperature was at 98°C.
The next version of board is designed with F28659DK8PTPQ1 controller. The datasheet mentions a junction temperature range of -40°C to +150°C.
What is the maximum safe junction temperature allowed during continuous operation, (ambient 71°C ) considering the safety level requirement?
Note: Controller ADC reference = 3.2V
Scale factor used for temperature measurement = 3.2/2.5 = 1.28 is multiplied with raw sensor reading.
