A front-end circuit with 16-channel 12-bit 100-kSps RC-hybrid SAR ADC for industrial monitoring application

Abstract

A front-end circuit with 16-channel 12-bit 100-kSps RC-hybrid successive approximation register (SAR) analog-to-digital converter (ADC) for industrial monitoring application is presented. The front-end circuit can process a wide range input voltage as large as 10 V which is beyond the supply voltage, with the help of voltage divider preceding an analog multiplexer. A programmable gain amplifier (PGA) is used to convert different input voltage ranges into a same one. A RC hybrid digital-to-analog converter (DAC) is employed in SAR ADC to avoid calibration requirement for the bridge capacitor which is usually needed for a split capacitor SAR ADC architecture. Serial peripheral interface (SPI) is integrated in the design for communication and configuration. The prototype circuit fabricated in a 0.18 um 3.3 V CMOS process shows the measured DNL and INL within −0.82/+0.68 LSB and −0.85/+0.82 LSB, respectively. The circuit consumes 2.04 mW with a 3.3 V supply voltage. The whole chip occupies an area of 1.844 × 1.387 mm2.