> REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 1 Abstract—This paper presents a 1.2V 36μW reconfigurable analog front-end (R-AFE) as a general-purpose low-cost IC for multiple- mode biomedical signals acquisition. The R-AFE efficiently reuses a reconfigurable preamplifier, a current generator (CG), and a mixed signal processing unit, having an area of 1.1mm 2 per R-AFE while supporting 5 acquisition modes to record different forms of cardiovascular and respiratory signals. The R-AFE can interface with voltage-, current-, impedance- and light-sensors and hence can measure electrocardiography (ECG), bio-impedance (BioZ), photoplethysmogram (PPG), galvanic skin response (GSR), and general-purpose analog (GPA) signals. Thanks to the chopper preamplifier and the low-noise CG utilizing dynamic element matching (DEM), the R-AFE mitigates 1/f noise from both the preamplifier and the CG for improved measurement sensitivity. The IC achieves competitive performance compared to the state- of-the-art dedicated readout ICs of ECG, BioZ, GSR and PPG, but with approximately 1.4x-5.3x smaller chip area per channel. Index Terms—reconfigurable, cardiovascular, respiratory, bio- impedance, multi-mode, dynamic element matching, ECG, GSR. I. INTRODUCTION HE long-term monitoring of cardiovascular and respiratory signs in a wearable format is a practical solution to improve user’s comfort and the diagnostic quality of chronic conditions. Two examples are congestive heart failure and obstructive sleep apnea. These chronic diseases are often characterized by high blood pressure, arrhythmias, respiratory disorders, body fluid overload, or even a heart attack. Therefore, low-power and miniaturized biomedical ICs that continuously measure these vital signs with medical-grade quality will improve chronic disease management and enable preventive healthcare. Many wearable medical ICs only focus on the acquisition and optimization of single vital sign for dedicated applications, such as electrocardiography (ECG) [1], bio-impedance (BioZ) [2], photoplethysmogram (PPG) [3] and so on. Integrating several ICs on the system level to enrich the bio-parameter matrix is not compact nor power-efficient. A multi-sensor ASIC (Fig. 1) [4] solves this problem by integrating several dedicated readout channels on a single chip. However, this often requires a large chip area (>10mm 2 ) and thus being expensive and less flexible. The reconfigurable AFEs (R-AFEs) [6][7] measure multimodal (bio-)signals while still being compact and low cost. They show promising results but the remaining challenges are performance optimization of noise, power dissipation and reconfigurability J. Xu, M. Konijnenburg, H. Ha, R. van Wegberg are with Holst Centre/imec, Eindhoven, 5656AE, The Netherlands (e-mail: jiawei.xu@imec-nl.nl). D. Blanco is with Institute for Bioengineering of Catalonia (IBEC), 08028, Barcelona, Spain. to meet the medical compliance [8]. This paper presents a low-power R-AFE for multimodal bio- signal acquisition [9]. It is highly reconfigurable among five acquisition modes, i.e., ECG mode for biopotential signals like ECG and EEG; BioZ mode for impedance cardiography (ICG) and respiration; galvanic skin response (GSR) mode for skin conductance representing cognitive state; PPG mode to detect blood oxygen saturation, heart rate and cardiac cycle; general- purpose analog (GPA) mode for other types of voltage inputs, e.g., a body temperature sensor, or a microphone to record body sounds (e.g. heartbeat, breathing). Apart from the multimodal recording, the R-AFE utilizes dynamic circuit techniques in the key building blocks to reduce 1/f noise for better sensitivity. II. ARCHITECTURE OVERVIEW AMP Reconfigurable Preamplifier: V/I/R sensing Reconfigurable Current Generator: AC/DC output Mixed Signal Processing: x1 12b ADC 500-4kS/s 1x-8x PGA 200-2kHz 40-150Hz LPF CIC ACU FIR fs/128, fs/4096, ② ③ ① ① ② ③ Fig. 2. Architecture of the reconfigurable analog-front-end (R-AFE) for multi- mode bio-signal acquisition The R-AFE (Fig. 2) includes a reconfigurable preamplifier, a low-noise current generator (CG), followed by a mixed signal processing chain to set channel settings, such as voltage gain, C. Van Hoof, S. Song and N. Van Helleputte are with imec, Heverlee, 3001, Belgium. A 36µW 1.1mm 2 Reconfigurable Analog Front-End for Cardiovascular and Respiratory Signals Recording Jiawei Xu, Mario Konijnenburg, Hyunsoo Ha, Roland van Wegberg, Shuang Song, Dolores Blanco-Almazán, Chris Van Hoof, and Nick Van Helleputte T EMG ECG EEG PPG Bio-Impedance GSR EOG PPG readouts BioZ readouts GSR readouts ExG readouts ADCs Existing Multimodal Bio-Interface Reconfigurable Analog Front-End Reconfigurable readout ADC Digital filters Fig. 1. Multimodal vital signs acquisition with dedicated readout channels or a reconfigurable readout channel