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∘ Cusing a precision switched-capacitor (SC) incrementalΔΣA/D converter. After batch calibration, an inaccuracy of±0.25∘ C~(±3)from-70∘ Cto 130∘ Cis 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∘ Cover 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 65μ Wduring 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.