An Ultra-Low-Power Successive-Approximation-Based ADC for Implantable Sensing Devices

Small area and power efficient analog-to-digital converters are needed to accommodate implantable multichannel sensors. This paper concerns the design and implementation of an ultra-low-power 8-bit successive approximation analog-to-digital converter (ADC). A new topology is proposed which improves the conventional architectures by replacing the successive approximation register and the digital-to-analog converter by a switchedopamp switched-capacitor circuit which dissipates very low power. The sampling frequency of the proposed ADC is 30 kSps and within an input range of 600 mV. Implemented in a 0.18-μm CMOS process with a 1.8 V voltage supply, the ADC achieves a power dissipation of 7.4 μW and occupies an area of 0.04 mm2.