A 0.12 mm$^{2}$ 7.4 $\mu$W Micropower Temperature Sensor With an Inaccuracy of $\pm$0.2$^{\circ}$C (3$\sigma$) From $-$30$^{\circ}$C to 125$^{\circ}$C

Abstract

This paper describes the design of a CMOS smart temperature sensor intended for RFID applications. The PNP-based sensor uses a digitally-assisted readout scheme that reduces the complexity and area of the analog circuitry and simplifies trimming. A key feature of this scheme is an energy-efficient two-step zoom ADC that combines a coarse 5-bit SAR conversion with a fine 10-bit ΣΔ conversion. After a single trim at 30°C, the sensor achieves an inaccuracy of ±0.2°C (3σ) from -30°C to 125°C. It also achieves a resolution of 15 mK at a conversion rate of 10 Hz. The sensor occupies only 0.12 mm² in a 0.16 μm CMOS process, and draws 4.6 μA from a 1.6 V to 2 V supply. This corresponds to a minimum power dissipation of 7.4 μW, the lowest ever reported for a precision temperature sensor.