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Temperature Sensor internal to MCU Vs External sensor

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Hello,
What would be decission factor to go with external temperaure sensor even though we have an internal temperature sensor to an MCU? How to calibrate the internal temperature sensor internal to an MCU? Please suggest me on this.
 

The main decision factor is how much increase you have from on-chip sensor to the point where you want to know it. It mostly depends on the power consumption of the chip. If it is low power and constant the you could calibrate to know the difference. Another way it to calculate it from the package to ambient resistor of the package (usually in the data sheet). Of course on-chip temp sensors could have less resolution, but you get it at zero cost.

Enjoy your design work!
 

The internal temperature is what you want and, since there is a built-in sensor on the chip, why not use it. The sensor is typically a forward biased silicon diode which has a fairly repeatable voltage to temperature value when biased with a small constant current. If you use the Shockley ideal diode voltage equation versus current and temperature, you should be close enough to the actual temperature for engineering purposes. If you measure the diode forward voltage at room temperature at the desired diode current as a calibration point, then you can use the diode equation to determine the temperature from the forward voltage at other temperatures.
 

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