An Ultra-Low Power Fixed-Window Level Crossing ADC for ECG Recording

In this paper, a novel fixed-window level-crossing analog-to-digital converter (LCADC) is proposed for the ECG monitoring application. The proposed circuit is implemented using fewer comparators and reference levels compared to the conventional structure, which results in a decrease in complexity and occupied silicon area. Also, the power consumption is reduced considerably by decreasing the activity of the comparator. Simulation results show a 5-fold reduction in activity by applying the standard ECG signals to the proposed structure. The proposed circuit is implemented in 0.18 µm CMOS technology using a 0.9 V supply voltage. Measurement results show a 5.9 nW power consumption and a 7.4-bit resolution. The circuit occupies a 0.05846 mm² silicon area. A typical level-crossing-based R-peak-detection algorithm is applied to the output samples of the LCADC, which shows the effectiveness of using this type of sampling.