A 151nW Second-Order Ternary Delta Modulator for ECG Slope Variation Measurement with Baseline Wandering Resilience

ECG delineation is crucial to Arrhythmia classification and future wearable heart monitoring sensors. This paper presents a second-order ternary delta modulator for ECG delineation. The proposed prototype measures slope variation of the ECG signals to detect the upward/downward-turning points without measuring the instantaneous amplitude. Then fiducial points of the PQRST waves can be located. The interval/segment timing information can be extracted for future on-chip arrhythmia classification. The experiment results show that the system is robust to baseline wandering. The chip can achieve 3.2 mV/ms
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sensitivity with 3 ms timing error. The proposed circuit consumes 151 nW with 1 V supply at a sampling rate of 1 kS/s, and fabricated in 180 nm CMOS process with 0.25 mm
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area occupied. Fiducial points localizing algorithm is realized on a Spartan-6 FPGA.