Low-Power CMOS Smart Temperature Sensor With a Batch-Calibrated Inaccuracy of ±0.25 °C (±3σ) from −70 °C to 130 °C

In this paper, a low-power CMOS smart temperature sensor is presented. The temperature information extracted using substrate PNP transistors is digitized with a resolution of 0.03 °C using a precision switched-capacitor (SC) incremental
A/D converter. After batch calibration, an inaccuracy of ±0.25 °C (±3σ ) from −70 °C to 130 °C is obtained. This represents a two-fold improvement compared to the state-ofthe-art. After individual calibration at room temperature, an
inaccuracy better than ±0.1 °C over the military temperature range is obtained, which is in-line with the state-of-the-art. This performance is achieved at a power consumption of 65 μW during a measurement time of 100 ms, by optimizing the power/inaccuracy tradeoffs, and by employing a clock frequency
proportional to absolute temperature. The latter ensures accurate settling of the SC input stage at low temperatures, and reduces the effects of leakage currents at high temperatures.