Journal Article•
A Low-Power CT Incremental 3rd Order ΣΔ ADC for Biosensor Applications.
TL;DR: In this article, a 3 rd order single-loop continuous-time incremental sigma-delta analogue-to-digital con- verter (ADC) for time-multiplexed signals is proposed.
Abstract: This paper proposes a 3 rd order single-loop continuous-time incremental sigma-delta analogue-to-digital con- verter (ADC) for time-multiplexed signals. Incremental sigma- delta modulation is used to address medium to high resolution requirements of multi-channel applications, while a 3 rd order continuous-time implementation is investigated as an alternative for low-power solutions. A prototype of the proposed modulator, running at 320 kHz, has been fabricated in a 0.15-µm CMOS technology, while the synchronization circuitry to allow incre- mental operation was built on-board. Measurement results show that the ADC achieves 65.3 dB peak SNR, 64 dB peak SNDR and 68.2 dB dynamic range over a 2 kHz bandwidth. The modulator's power dissipation is 96 µW from a 1.6 V power supply. This translates into the best figure-of-merit when compared to recently published continuous-time alternatives, while being competitive with respect to state-of-the-art discrete-time counterparts. Index Terms—A/D conversion, incremental ADC, continuous-time.
Citations
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TL;DR: Fundamental principles and state-of-the-art technologies for electrode-tissue impedance measurement, photoplethysmography, functional near-infrared spectroscopy, and signal coding and quantization are reviewed, with additional guidelines for overall power management including wireless transmission.
Abstract: This paper presents an overview of the fundamentals and state of the-art in noninvasive physiological monitoring instrumentation with a focus on electrode and optrode interfaces to the body, and micropower-integrated circuit design for unobtrusive wearable applications. Since the electrode/optrode-body interface is a performance limiting factor in noninvasive monitoring systems, practical interface configurations are offered for biopotential acquisition, electrode-tissue impedance measurement, and optical biosignal sensing. A systematic approach to instrumentation amplifier (IA) design using CMOS transistors operating in weak inversion is shown to offer high energy and noise efficiency. Practical methodologies to obviate 1/f noise, counteract electrode offset drift, improve common-mode rejection ratio, and obtain subhertz high-pass cutoff are illustrated with a survey of the state-of-the-art IAs. Furthermore, fundamental principles and state-of-the-art technologies for electrode-tissue impedance measurement, photoplethysmography, functional near-infrared spectroscopy, and signal coding and quantization are reviewed, with additional guidelines for overall power management including wireless transmission. Examples are presented of practical dry-contact and noncontact cardiac, respiratory, muscle and brain monitoring systems, and their clinical applications.
100 citations
TL;DR: This paper presents an analog-to-digital converter (ADC) dedicated to neural recording systems that can achieve high-resolution without sacrificing the conversion rate by using two continuous-time incremental sigma-delta ADCs in a pipeline configuration.
Abstract: This paper presents an analog-to-digital converter (ADC) dedicated to neural recording systems. By using two continuous-time incremental sigma-delta ADCs in a pipeline configuration, the proposed ADC can achieve high-resolution without sacrificing the conversion rate. This two-step architecture is also power-efficient, as the resolution requirement for the incremental sigma-delta ADC in each step is significantly relaxed. To further enhance the power efficiency, a class-AB output stage and a dynamic summing comparator are used to implement the sigma-delta modulators. A prototype chip, designed and fabricated in a standard 0.18 $\mu{\rm m}$ CMOS process, validates the proposed ADC architecture. Measurement results show that the ADC achieves a peak signal-to-noise-plus-distortion ratio of 75.9 dB over a 4 kHz bandwidth; the power consumption is 34.8 $\mu{\rm W}$ , which corresponds to a figure-of-merit of 0.85 pJ/conv.
71 citations
TL;DR: An integrated circuit that merges integrated optical and temperature transducers, optical interface circuitry, and a near-field communication (NFC)-enabled digital, wireless readout for a fully passive implantable sensor platform to measure glucose in people with diabetes is presented.
Abstract: This paper presents an integrated circuit (IC) that merges integrated optical and temperature transducers, optical interface circuitry, and a near-field communication (NFC)-enabled digital, wireless readout for a fully passive implantable sensor platform to measure glucose in people with diabetes. A flip-chip mounted LED and monolithically integrated photodiodes serve as the transduction front-end to enable fluorescence readout. A wide-range programmable transimpedance amplifier adapts the sensor signals to the input of an 11-bit analog-to-digital converter digitizing the measurements. Measurement readout is enabled by means of wireless backscatter modulation to a remote NFC reader. The system is able to resolve current levels of less than 10 pA with a single fluorescent measurement energy consumption of less than 1 μJ. The wireless IC is fabricated in a 0.6-μm-CMOS process and utilizes a 13.56-MHz-based ISO15693 for passive wireless readout through a NFC interface. The IC is utilized as the core interface to a fluorescent, glucose transducer to enable a fully implantable sensor-based continuous glucose monitoring system.
45 citations
TL;DR: A nonlinearity compensation technique for Gm-C-based ΣΔ modulator which designs a nonlinear feedback DAC which has matched V-I transfer curve as the first Gm amplifier (Gm1) so that the distortions of Gm1 are significantly suppressed at the modulator output.
Abstract: Wideband ( $\geq$ 10 MHz) continuous-time (CT) sigma-delta $(\Sigma\Delta)$ modulators generally use active-RC filters. On the other hand, Gm-C-filters avoid the need of a power-hungry driving stage due to their small loading. At the moment, the major challenge for designing Gm-C-based $\Sigma\Delta$ modulator is the narrow linear input range due to the nonlinear Gm amplifier, which leads to low SNDR. This work develops a nonlinearity compensation technique for Gm-C-based $\Sigma\Delta$ modulator. This technique designs a nonlinear feedback DAC which has matched V-I transfer curve as the first Gm amplifier (Gm1). As a result, the distortions of Gm1 are significantly suppressed at the modulator output. This method is prototyped in a 640 MS/s Gm-C-based $\Sigma\Delta$ modulator with 10 MHz signal bandwidth in a 0.18- $\mu{\rm m}$ CMOS process. With this technique, the linear input range of the modulator is greatly enlarged. Consequently, the peak SNDR of the modulator is improved by about 8 dB to 75 dB. This $>$ 12-bit ENOB is achieved for the first time for wide-band Gm-C-based $\Sigma\Delta$ modulators.
19 citations
TL;DR: A new biophotometry sensor merging two individual building blocks, namely a low-noise sensing front-end and a order continuous-time CTSDM modulator, into a single module for enabling high-sensitivity and high energy-efficiency photo-sensing.
Abstract: Fluorescence biophotometry measurements require wide dynamic range (DR) and high-sensitivity laboratory apparatus. Indeed, it is often very challenging to accurately resolve the small fluorescence variations in presence of noise and high-background tissue autofluorescence. There is a great need for smaller detectors combining high linearity, high sensitivity, and high-energy efficiency. This paper presents a new biophotometry sensor merging two individual building blocks, namely a low-noise sensing front-end and a $2\text{nd}$ order continuous-time $\Sigma \Delta$ modulator (CTSDM), into a single module for enabling high-sensitivity and high energy-efficiency photo-sensing. In particular, a differential CMOS photodetector associated with a differential capacitive transimpedance amplifier-based sensing front-end is merged with an incremental $2\text{nd}$ order 1-bit CTSDM to achieve a large DR, low hardware complexity, and high-energy efficiency. The sensor leverages a hardware sharing strategy to simplify the implementation and reduce power consumption. The proposed CMOS biosensor is integrated within a miniature wireless head mountable prototype for enabling biophotometry with a single implantable fiber in the brain of live mice. The proposed biophotometry sensor is implemented in a 0.18- $\mu \text{m}$ CMOS technology, consuming $\text{41}\ \mu \text{W}$ from a 1.8- $\text{V}$ supply voltage, while achieving a peak dynamic range of $\text{86}\ \text{dB}$ over a 50- $\text{Hz}$ input bandwidth, a sensitivity of 24 mV/nW, and a minimum detectable current of 2.46- $pA_{\rm rms}$ at a 20- $\text{kS/s}$ sampling rate.
15 citations
References
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01 Jan 1978
TL;DR: A comprehensive catalog of data windows along with their significant performance parameters from which the different windows can be compared is included, and an example demonstrates the use and value of windows to resolve closely spaced harmonic signals characterized by large differences in amplitude.
Abstract: This paper makes available a concise review of data windows and their affect on the detection of harmonic signals in the presence of broad-band noise, and in the presence of nearby strong harmonic interference. We also call attention to a number of common errors in the application of windows when used with the fast Fourier transform. This paper includes a comprehensive catalog of data windows along with their significant performance parameters from which the different windows can be compared. Finally, an example demonstrates the use and value of windows to resolve closely spaced harmonic signals characterized by large differences in amplitude.
7,130 citations
Book•
01 Jan 1997
TL;DR: Delta-Sigma Data Converters provides comprehensive coverage of low and high-order single-bit, bandpass, continuous-time, multistage modulators as well as advanced topics, including idle-channel tones, stability, decimation and interpolation filter design, and simulation.
Abstract: This comprehensive guide offers a detailed treatment of the analysis, design, simulation and testing of the full range of today's leading delta-sigma data converters. Written by professionals experienced in all practical aspects of deltasigma modulator design, Delta-Sigma Data Converters provides comprehensive coverage of low and high-order single-bit, bandpass, continuous-time, multistage modulators as well as advanced topics, including idle-channel tones, stability, decimation and interpolation filter design, and simulation.
1,879 citations
TL;DR: It is demonstrated here for the first time that electrocorticographic (ECoG) activity recorded from the surface of the brain can enable users to control a one-dimensional computer cursor rapidly and accurately.
Abstract: Brain–computer interfaces (BCIs) enable users to control devices with electroencephalographic (EEG) activity from the scalp or with single-neuron activity from within the brain Both methods have disadvantages: EEG has limited resolution and requires extensive training, while single-neuron recording entails significant clinical risks and has limited stability We demonstrate here for the first time that electrocorticographic (ECoG) activity recorded from the surface of the brain can enable users to control a one-dimensional computer cursor rapidly and accurately We first identified ECoG signals that were associated with different types of motor and speech imagery Over brief training periods of 3–24 min, four patients then used these signals to master closed-loop control and to achieve success rates of 74–100% in a one-dimensional binary task In additional open-loop experiments, we found that ECoG signals at frequencies up to 180 Hz encoded substantial information about the direction of two-dimensional joystick movements Our results suggest that an ECoG-based BCI could provide for people with severe motor disabilities a non-muscular communication and control option that is more powerful than EEG-based BCIs and is potentially more stable and less traumatic than BCIs that use electrodes penetrating the brain M This article features online multimedia enhancements
1,182 citations
TL;DR: New technology to engineer the tissue-electrode interface, electrode design, and extraction algorithms to transform the recorded signal to movement will help translate exciting laboratory demonstrations to patient practice in the near future.
796 citations
TL;DR: It is shown that a brain-computer interface using electrocorticographic activity (ECoG) and imagined or overt motor tasks enables humans to control a computer cursor in two dimensions and supports the expectation that ECoG-based BCIs can combine high performance with technical and clinical practicality.
Abstract: We show here that a brain-computer interface (BCI) using electrocorticographic activity (ECoG) and imagined or overt motor tasks enable humans to control a computer cursor in two dimensions. Over a brief training period of 12-36 min, each of five human subjects acquired substantial control of particular ECoG features recorded from several locations over the same hemisphere, and achieved average success rates of 53-73% in a two-dimensional four-target center-out task in which chance accuracy was 25%. Our results support the expectation that ECoG-based BCIs can combine high performance with technical and clinical practicality, and also indicate promising directions for further research.
486 citations