An ultra-low power robust CMOS temperature Sensor with an inaccuracy of ±0.7°C from -40°C to 85°C

Abstract

An ultra-low power robust CMOS temperature sensor is presented for RFID. The BJT-based sensor employs a calibrated hybrid ADC, which combines a coarse 5-bit SAR conversion with a fine 9-bit delta-sigma conversion. For the purpose of being robust, an error correction method is proposed in this paper, which can calibrate the SAR errors caused by power supply and mismatch. A smart clock generator is also proposed to adapt the change of PTAT bias current, which provides the integrators more settling time in low temperature with low bias current and makes the delta-sigma ADC faster in high temperature to reduce the error caused by leakage. The sensor has been implemented in a 130nm CMOS process. After a one-point temperature trimming, the sensor has a resolution of 0.015 from -40°C to 85°C, and only consumes 10 μA from 1.5V supply.