A Low-Power CMOS Analog Front-End IC with Adjustable On-Chip Filters for Biosensors

Donald Y. C. Lie, Vighnesh Das, Weibo Hu, Yenting Liu, Tam Nguyen

Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, USA.
Department of Surgery, Texas Tech University Health Sciences Center, Texas Tech University, Lubbock, USA.

DOI: 10.4236/ojab.2013.24014                

Abstract

This paper presents a low-power CMOS analog front-end (AFE) IC designed with a selectable on-chip dual AC/DC- coupled paths for bio-sensor applications. The DC-coupled path can be selected to sense a biosignal with useful DC information, and the AC-coupled path can be selected for sensing the AC content of the biosignal by attenuating the unwanted DC component. The AFE IC includes a DC-coupled instrumentation amplifier (INA), two variable-gain 1^st-order low pass filters (LPF) with tunable cut-off frequencies, a fixed gain 2^nd-order Sallen-Key high-pass filter (HPF) with tunable cut-off frequencies, a buffer and an 8-bit differential successive approximation register (SAR) ADC. The entire AFE channel is designed and fabricated in a proprietary 0.35-μm CMOS technology. Excluding an external buffer needed to properly drive the ADC, the measured AFE IC consumes only 2.37 μA/channel with an input referred noise of ~40 μV_rms in [1 Hz, 1 kHz], and successfully displays proper ECG (electrocardiogram) and electrogram (EGM) waveforms for QRS peaks detection. We expect that the low-power dual-path design of this AFE IC can enable it to periodically record both the AC and the DC signals for proper sensing and calibration for various bio-sensing applications.

Keywords

Low-Power CMOS; Bio-Sensor Applications; DC-Coupled

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	L. S. Y. Wong, S. Hossain, A. Ta, J. Edvinsson, D. H. Rivas and H. Naas, “A Very Low-Power CMOS Mixed-Signal IC for Implantable Pacemaker Applications,” IEEE Journal of Solid-State Circuits, Vol. 39, No. 12, 2004, pp. 2446-2456. http://dx.doi.org/10.1109/JSSC.2004.837027
[2]	W. Hu, T. Nguyen, Y.-T. Liu and D.Y.C. Lie, “Ultralow Power Analog Front-End Circuits and System Design for an Implantable Cardioverter Defibrillator,” Proceedings of the IEEE-NIH Life Science Systems and Application Workshop, 2011, pp. 34-37.
[3]	X. D. Zou, X. Y. Xu, L. B. Yao and Y. Lian, “A 1-V 450-nW Fully Integrated Programmable Biomedical Sensor Interface System,” IEEE Journal of Solid-State Cir- cuits, Vol. 44, No. 4, 2009, pp. 1067-1077. http://dx.doi.org/10.1109/JSSC.2009.2014707
[4]	N. Verma, A. Shoeb, J. Bohorquez, J. Dawson, J. Guttag and A. P. Chandrakasan, “A Micro-Power EEG Acquisition SoC with Integrated Feature Extraction Processor for a Chronic Seizure Detection System,” IEEE Journal of Solid-State Circuits, Vol. 45, No. 4, 2010, pp. 804-816. http://dx.doi.org/10.1109/JSSC.2010.2042245
[5]	X. Liu, Y. Zheng, M. W. Phyu, F. N. Endru, V. Navanee-than and B. Zhao, “An Ultra-Low Power ECG Acquisition and Monitoring ASIC System for WBAN Application,” IEEE Journal of Emerging and Selected Topics in Circuits and System, Vol. 2, No. 1, 2012, pp. 60-70. http://dx.doi.org/10.1109/JETCAS.2012.2187707
[6]	R. Harrison and C. Charles, “A Low-Power Low-Noise CMOS Amplifier for Neural Recording Applications,” IEEE Journal of Solid-State Circuits, Vol. 38, No. 6, 2003, pp. 958-965. http://dx.doi.org/10.1109/JSSC.2003.811979
[7]	www.ti.com/product/ADS1291
[8]	E. Sackinger and W. Gug-genbuhl, “A Versatile Building Block: The CMOS Differential Difference Amplifier,” IEEE Journal of Solid-State Circuits, Vol. 22, No. 2, 1987, pp. 287-294.
[9]	R. Schreier and G. C. Temes, “Understanding Delta-Sigma Data Converters”, 1st Edition, IEEE Press, New Jersey, 2007.
[10]	W. Hu, Y.-T. Liu, D. Y. C. Lie and B. P. Ginsburg, “An 8-Bit Single-Ended Ultra-Low-Power SAR ADC with Novel DAC Switching and Digital Control Circuits for Bio-Medical Applications’,” IEEE Transactions on Circuits and Systems-I (TCAS-I), Vol. 60, No. 7, 2013, pp. 1726-1739.
[11]	www.physionet.org/physiobank/database/iafdb
[12]	A. Gerosa, A. Maniero and A. Neviani, “A Fully Integrated Two-Channel A/D Interface for the Acquisition of Cardiac Signals in Implantable Pacemakers,” IEEE Journal of Solid-State Circuits, Vol. 39, No. 7, 2004, pp. 1083-1093. http://dx.doi.org/10.1109/JSSC.2004.829921