Low-Power CMOS Smart Temperature Sensor With a Batch-Calibrated Inaccuracy of ${\pm}{0.25}^{\circ}{\rm C}~({\pm}3\sigma)$ From ${-}{70}^{\circ}{\rm C}$ to 130 $^{\circ}{\rm C}$

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
$^{\circ}{\rm C}$
using a precision switched-capacitor (SC) incremental
$\Delta\Sigma$
A/D converter. After batch calibration, an inaccuracy of
${\pm}0.25^{\circ}{\rm C}~({\pm}{3})$
from
${-}{70}^{\circ}{\rm C}$
to 130
$^{\circ}{\rm C}$
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
${\pm}{\rm 0.1}^{\circ}{\rm C}$
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
$\mu{\rm W}$
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.