Ultra-low-power fully-synchronous level-crossing analog-to-digital converter for biomedical signal acquisition

In this paper, an ultra-low power analog-to-digital converter (ADC) is proposed which is working based on level-crossing sampling. Level-crossing sampling is a data-compression technique utilizing specially for low-power implementation of biomedical signal acquisition systems. Despite the non-uniform nature of level-crossing sampling, the proposed ADC is implemented synchronously which leads to much lower power consumption and improved reliability. Accuracy of the ADC is improved by using a modified structure for dynamic comparators. A low-cost tuning circuit is also proposed for canceling a great portion of the background noise, which leads to a more efficient compression. The ADC is designed for ECG signal acquisition and implemented in 0.18 μm CMOS technology which consumes an ultra low power of 28 nW for 1.8 V supply voltage.