Operating Principle
Silicon-based temperature sensors exploit the linear relationship between absolute temperature and the difference in base-emitter voltages of two bipolar junction transistors operating at different current densities. Analog and digital control loops utilize a PTAT sensor to monitor the temperature of silicon dies and provide the feedback needed for thermal compensation. This type of sensor generates an output voltage or current that scales linearly with temperature, providing a predictable and stable measurement.
The linear response minimizes the complexity of the correction algorithms, reducing the memory and processor power required by the host microcontroller.
Circuit Topology
The sensing element is paired with a bandgap reference circuit to generate both a temperature-dependent signal and a stable, temperature-independent reference voltage. This configuration enables the sensor to operate with low supply voltages while maintaining high sensitivity to temperature changes.
Calibration Accuracy
Manufacturing variations in transistor geometry and doping concentrations can cause offset shifts and scale factor errors in the sensor output. To achieve high accuracy, these sensors are calibrated at the wafer level using a two-point thermal calibration process that calculates correction coefficients for each device.
Direct Integration
Direct integration of these sensors into microcontrollers, analog-to-digital converters, and pressure sensors provides real-time temperature data. This proximity to the primary sensing elements allows for immediate compensation of thermal drifts, ensuring the stability of the overall system.
