5.4 A Hybrid Thermal-Diffusivity/Resistor-Based Temperature Sensor with a Self-Calibrated Inaccuracy of ±0.25° C(3 Σ) from -55°C to 125°C

Resistor-based temperature sensors can achieve higher resolution and energy-efficiency than traditional BJT-based sensors. To reach similar accuracy, however, they typically require 2-point (2-pt) calibration, compared to the low-cost 1-pt calibration required by BJT-based sensors. This paper presents a hybrid temperature sensor that uses an inherently accurate, but power-hungry, thermal-diffusivity (TD) sensor [1] to self-calibrate an inaccurate, but efficient, resistor-based sensor [2]. The use of an on-chip reference obviates the need for accurate temperature stabilized ovens or oil baths, drastically reducing calibration time and costs. Furthermore, by sharing most of the readout circuitry, the associated area overhead can be reduced. After self-calibration at room temperature (RT, $\sim 25^{\circ}\mathrm{C})$ and at an elevated temperature $(\sim 85^{\circ}\mathrm{C})$, the proposed hybrid temperature sensor achieves an inaccuracy of $0.25^{\circ}\mathrm{C} (3^{\sigma})$ from $-55^{\circ}\mathrm{C}$ to $125^{\circ}\mathrm{C}$.