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Next-generation wearable devices will enable clinical-grade, continuous ExG (ECG, EEG, EMG, etc.) biopotential monitoring, providing medical professionals with valuable longitudinal data outside of hospital settings. These devices must be ultra-low power (<; 10μW) to enable long battery life while accurately digitizing sub-kHz, μV-level ExG signals in the presence of large motion and/or stimulation art ifacts (>100mV) with high input-impedance (Zin>10MΩ) to avoid signal attenuation. Achieving such performance with conventional PGA+ADC architectures is challenging due to the conflicting low-power and >90dB dynamic-range (DR) requirements [1]. To address this, several direct digitization analog front-ends (AFEs) have been reported [2-4]. While these offer wide DR, they typically have low input-impedance (<; 5MΩ) and/or low power-efficiency (FoM≤172dB). This paper presents a scalable 2nd-order voltage …