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 degrees C using a precision switched-capacitor (SC) incremental Delta Sigma A/D converter. After batch calibration, an inaccuracy of +/- 0.25 degrees C (+/- 3 sigma) from -70 degrees C to 130 degrees C is obtained. This represents a two-fold improvement compared to the state-of-the-art. After individual calibration at room temperature, an inaccuracy better than +/- 0.1 degrees 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 mu W 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.