Hey, here are 4 ways to measure the temperature of small package chips~

There are several ways to measure junction temperature or chip temperature, and some methods are better than others. Today I will introduce 4 methods to you:

Given below is the classic junction temperature equation:

T _J = T _A + P _D ϑJA

The junction temperature, _TJ, is equal to the ambient temperature, _TA, plus the product of the device power dissipation, _PD, and the device thermal resistance, θJA _. In my experience, this calculation is quite conservative and the resulting junction temperature is approximately 30% to 50% higher than the actual junction temperature, depending on the manufacturer.

This measurement method is relatively accurate for larger packages, but becomes problematic when used with smaller packaged devices. For example, small packages such as SC70 or SOT have less area to attach a thermocouple. Even if you can attach a thermocouple to a package, the thermal mass of the thermocouple actually acts as a heat sink, drawing some heat away from the device, which can introduce errors into the measurement.

This method actually measures the case temperature outside the package and can accurately measure the chip temperature of smaller packages. In most cases, the difference between the case temperature and the junction temperature is only a few degrees. The disadvantage of this method is that infrared cameras are often quite expensive, about tens of thousands of dollars.

This is the most economical and accurate method. From the perspective of semiconductor physics, we know that after applying a constant current source to a PN junction, the junction voltage changes with temperature by about -1 mV/°C to -2 mV/°C. Characterizing the change in diode voltage with temperature allows the user to measure the diode voltage and easily determine the chip temperature. The trick is to find a diode that can be used as a sensor in the op amp. Most op amps do not provide dedicated temperature measurement diodes, but you can make existing diodes perform the temperature measurement function.

Most, if not all, amplifiers today have built-in electrostatic discharge (ESD) protection diodes as well as input protection diodes. The ESD diodes connect the input and output of the amplifier to provide the swing. Therefore, these diodes can be connected and used as an outlined measurement of the op amp’s die temperature.

Have you got all the methods to measure the temperature of small package chips? Leave your opinions and views at the end of the article and you may get a wonderful gift~