1 Introduction

When monitoring the temperature of critical components in a system, better accuracy leads to better information feedback to temperature control loops used for compensation or safety shutdown purposes. In some ICs, designers include a thermal diode pin, which connects to an external temperature sensor to monitor the internal temperature of the die. This method is viable when the internal diode-connected transistor used for temperature sensing is well-constructed and has an overtemperature behavior which closely follows that of a standard BJT.

Some ICs may not have an internal thermal transistor designed in, or its overtemperature characteristics may provide poor quality for temperature detection. Instead, the designer may choose to use the internal temperature sensor of the device if one is available. One main disadvantage of the included temperature sensing element in most ICs is that they have extremely low accuracy—typically on the order of ± 5°C to 10°C—because process deviation in silicon can be 15% or more, which leads to high temperature errors in the die.

There are several options for measuring the temperature of the desired component. Option 1 is to use the internal diode or temperature sensor, if available. Option 2 is to place an external integrated temperature sensor or thermistor on the PCB as close as possible to the heat source. Finally, option 3 is to calculate the temperature of the component by taking differential temperature measurements. Option 3 enables highly-accurate temperature monitoring using a dedicated thermal layout (for example, a ground plane, heat sink, or dedicated thermal trace) and two temperature sensors, such as TI’s TMP6 thermistors.