Low Power High-Resolution Smart Temperature Sensor for Autonomous Multi-Sensor System

A low power temperature sensor followed by a switched capacitor amplifier, a buffer stage, and a 12-bit successive approximation analogue-to-digital converter (ADC) for autonomous multi-sensor systems is presented. The proposed design is accurate within 0.01 degrees C from -55 degrees C to 125 degrees C. A proportional to absolute temperature source was used as a temperature sensor. The read-out enables a differential reading of a reference and actual temperature. The subsequent ADC digitizes the output signal. The ADC has a figure-of-merit of 66 fJ/conversion-step at a bit-clock of 50 kHz. The system is implemented in an NXP CMOS 0.14-mu m technology. The die area is 0.27 mm(2), and the whole system consumes less than 16 mu W. Design and measurements are presented.