A 0.12 mm2 7.4 μW Micropower Temperature Sensor With an Inaccuracy of ±0.2°C (3σ) From-30°C to 125°C

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 Sigma Delta conversion. After a single trim at 30 degrees C the sensor achieves an inaccuracy of +/- 0.2 degrees C (3 sigma) from -30 degrees C to 125 degrees C. It also achieves a resolution of 15 mK at a conversion rate of 10 Hz. The sensor occupies only 0.12 mm(2) in a 0.16 mu m CMOS process, and draws 4.6 mu A from a 1.6 V to 2 V supply. This corresponds to a minimum power dissipation of 7.4 mu W, the lowest ever reported for a precision temperature sensor.