A 0.6V 75nW All-CMOS Temperature Sensor With 1.67m°C/mV Supply Sensitivity

This paper presents the design of a fully-integrated ultra-low-power temperature sensor applicable for use in wearable, environmental monitoring, and Internet-of-Things applications. Temperature is transduced in the proposed design by charging a pair of capacitors with proportional to or complementary to (proportional to absolute temperature or complementary to absolute temperature) current sources, and converting temperature-varying charging times to digital via a time-to-digital converter clocked by an on-chip temperature- and supply-stabilized 30-kHz relaxation oscillator. A low-voltage pseudo-differential dual-loop current reference generator is employed alongside inverter-based comparators to impart supply- and temperature-stable performance at low power. Fabricated in $0.18\mu \text{m}$ CMOS, the design operates at 0.6 V and consumes 75 nW at room temperature. Across a temperature range of 0 °C-100 °C, the sensor achieves a best-case (worst-case) temperature accuracy of +0.47 °C/-0.22 °C (+0.62 °C/-1.33 °C) and a resolution of 0.093 °C (0.1 °C). Across a supply range of 0.55--0.85 V, the sensor achieves an inaccuracy of +0.19 °C/-0.28 °C.