An SoC-Integrated sensor based on SAR ADC for simultaneous temperature and voltage monitoring

Abstract

In this paper, a smart system monitoring sensor based on a 12-bit SAR ADC with hybrid DAC is presented, and fabricated in a standard 55-nm CMOS process. By utilizing a MUX to switch the input channel, monitoring of the temperature and voltage at critical points is achieved. Additionally, a double conversion method is also proposed for circumventing the current mismatches of the two BJT temperature sensing elements, thereby lower the circuit complexity. For temperature sensing, the sensor shows a measured inaccuracy of ±1.5℃ from -55℃ to 125℃ with an resolution of 0.86℃. For voltage sensing, the ADC shows a measured DNL and INL of +0.43/-0.47LSB and +1.4/-1.1LSB, respectively. Thanks to the proposed technique, the sensor consumes low power of 182μW under a 1.8/1.2V supply at a conversion speed of 156kS/s, and occupies an area of 0.074mm².