Feasibility of Successive Approximation Register ADC in Ultra Low Power Biomedical Applications

Analog-to-Digital Converter (ADC) is a critical block of the sensing unit of an implant and for measurements of various biophysiological signals, such as Electrocardiogram (ECG), Electroencephalogram (EEG) and Electromyogram (EMG) that covers the distinct portions of the frequency spectrum and signal bandwidths. ADC consumes about 30~35% of the total power of the device which is very high. Hence, for biomedical implants which require ultra low power consumption and low complexity to reduce the size and cost of the devices, there is a need of energy-efficient ADCs that conform to these restraints. This paper presents a study on the feasibility of ultra low power Successive Approximation Register (SAR) ADC in these biomedical applications. Various SAR ADC architectures proposed in the past decade to achieve ultra low power consumption have been investigated and their performances have been compared with respect to the parameters such as resolution, sampling frequency, signal–to-noise and distortion ratio, figure of merit among others. This paper also discusses the different switching schemes proposed to reduce the switching power consumed by the DAC. Finally, the future research scope and areas to further achieve ultra low power consumption without degrading the overall performance of the ADC has also been presented. Keyword-ADC, Biomedical Applications, SAR, Ultra Low Power Electronics