A MOS-Based Temperature Sensor With Energy-Efficient Techniques

Abstract

This letter presents an energy-efficient MOS-based temperature sensor, enhanced through transducer and readout circuit integrated design, LSB-first SAR, and energy-efficient comparator. The transducer and readout circuit integrated design reduces noise by combining two blocks into one. With temperature-dependent offset voltage, the comparator integrates with the LSB-first SAR and is optimized for energy efficiency. The LSB-first SAR reduces the number of cycles and energy consumption. In addition, an asynchronous clock controls the circuit, eliminating the need for a timing reference and adjusting speed to temperature to increase measurement robustness. The temperature sensor was fabricated with a 65 nm CMOS process, and the sensor has −60 to $145~^{\circ }$ C measurement range. After two-point calibration with a second-order polynomial, errors are −1.93/ ${+} 1.44~^{\circ }$ C over the entire range and −0.96/ ${+} 0.94~^{\circ }$ C from −43 to $137~^{\circ }$ C. At room temperature, the sensor achieves 71.8 mK resolution and 41.9 pJ per conversion, resulting in the best resolution figure-of-merit of 216 fJ $\cdot $ K2 among MOS-based sensors.