A Code-Recombination Algorithm-Based ADC With Feature Extraction for WBSN Applications

This article presents a low-power code-recombination (CR) analog-to-digital converter (ADC) with generic feature extraction for wearable electrocardiogram (ECG) sensors in wireless body sensor network (WBSN) applications. The CR ADC features a search forward procedure (SFP) and a search backward procedure (SBP) to hunt for part of the quantization steps cutting down bitcycle and power consumption. Also, CR ADC outputs a digital stream named $K$ data served as a compressed feature. A prototyped chip including a proposed ADC is fabricated in a 0.13- $\mu \text{m}$ CMOS process. With a 0.6-V supply voltage and a 10-kS/s sampling rate, the measured signal-to-noise-distortion range (SNDR) and spurious-free dynamic range (SFDR) are 58.34 and 70.2 dB, respectively. The ADC consumes only 40-nW power when input residue is within the prediction range defined by ADC’s resolution and the reference voltage, achieving a figure-of-merit (FoM) of 6.2 fJ/conversion-step. The data $K$ occupy 2/5 of the raw data and are conducted to categorize cardiovascular diseases illustrating at least 96% accuracy.