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The first fully integrated oven-controlled temperature compensation system with the transformer coupled Colpitts oscillator is developed by 65nm CMOS tech. This work achieves ±1.55ppm frequency stability over the 85°C temperature range which can be used for the GPS application (<2ppm). An integrated heater in the FBAR chip consumes 14mW power at maximum. The temperature resolution of TDC is 150uK,...
Low power and low noise RF frequency reference is essential for radio system. Radio standards require reference frequency to be stable over a wide range of temperatures (−40 to 110°C for industrial). The state of the art radio architecture used temperature compensated resonator (ZDR), but the stability is not enough to meet the most stringent spec. for GPS application (<2ppm). The solution is here...
We present the proposed oscillator architecture to reduce the close-in phase noise as well as power consumption. The proposed Colpitts oscillator removes the current source which is the main source of the 1/f noise conversion. The removal of the current source is compensated by the transformer and cross coupled capacitors. The 2GHz FBAR is used for the high Q frequency selective elements in the oscillator...
Neuroscientists are increasingly engaging the integrated circuit (IC) community to develop new tools for understanding the brain. Fundamental research performed on small animal models, for example, requires miniaturized instrumentation for long term freely behaving studies. Recording from non-human primates, rats, mice, and even insects is of interest. This research, in turn, will lead to advanced...
An electrode in neural tissue can often detect action potentials from multiple neurons. Spike sorting is the task of distinguishing which spikes came from which neurons. It is made feasible by the fact that spikes from a single neuron tend to have a characteristic shape [5].
Having discussed the critical components of implantable neural interfaces, we may now move on to system integration issues. After reviewing some previous systemlevel efforts, this chapter and the next will describe two example systems, both including signal acquisition circuitry and a wireless communication link.
The signal path in a neural recording system must typically start with an amplifier in order to boost the signal levels and buffer the high source impedance. Because of the small signal amplitudes, amplifier noise must be minimized in order to avoid unnecessary degradation of the signal. Additionally, the high impedance of neural electrodes necessitates a high impedance input.
There are many design challenges involved in the circuit design of implantable neural recording systems. A generic biopotential-recording system is illustrated in Fig. 2.1. First, weak neural signals must be amplified, conditioned, and then digitized. The information then needs to be wirelessly transmitted out of the body to avoid possible infection from transcutaneous connectors. The power consumption...
One observation from the two neural amplifiers described in the previous two chapters is the dominance of flicker noise. Most of the existing power-noise optimization techniques target thermal noise. However, flicker noise is a significant concern for EMG/EEG/ECoG applications, where the bandwidth of interest is much lower (<500Hz) than that of neural applications (∼10kHz). Therefore, we will devote...
Implantable neural interfaces have the potential to revolutionize medicine and neuroscience research. One of the key challenges to realization of this potential is reduction of power consumption. This book has described micro-power circuit implementations for several key building blocks of a neural interface.
In this chapter, we will present the measurement results of the telescopic-cascode and complementary low-noise amplifiers discussed in the previous chapter. In order to compare and contrast the performance of these two LNA designs, we fabricated both LNAs in a 0.13 μm CMOS process. As the analog front-end of a neuralrecording channel, each LNA is followed with a variable-gain amplifier (VGA) to accommodate...
As previously described, in order to accommodate weak neural signals, we need sufficient amplification and signal conditioning at the front-end of a neural-recording system. Specifically, the requirements on the front-end amplifier can be summarized as below: Input-referred noise voltage < 10 μ V Midband gain ≌ 40 dB Input impedance ≥ a few...
This chapter describes the mapping of a clustering algorithm into analog circuits and the design of the constituent circuit blocks. The experimental characterization of the individual blocks and of the clustering system are described. The clustering algorithm implemented is based on the K-Means algorithm, but differs in that the magnitude of the updates is independent of the input.
This chapter describes a fully integrated neural interface which wirelessly streams a digitized neural waveform over 15m [2]. In contrast to the NeuralWISP described in the previous chapter, this system is designed to operate from a small battery. The battery allows the system to operate at a greater range from the receiver and to transmit more data. Because of the low power consumption in the analog...
In neural recording applications focused on action potentials, one of the first signal processing tasks is to distinguish the spikes from noise and interference. In this chapter we will discuss the requirements for a spike detector, review several implementations, and describe in detail a low-power spike detector utilizing the nonlinear energy operator and operating in the analog domain. Once a spike...
Micro-power Integrated Circuits for Neural Interfaces Jeremy Holleman Fan Zhang Brian Otis This book describes ultra low-power, integrated circuits and systems designed for the emerging field of neural signal recording and processing, and wireless communication. Since neural interfaces are typically implanted, their operation is highly energy-constrained. This book introduces concepts and theory that...
A low-power sensor interface IC suitable for a differential frequency measurement application is demonstrated. The circuit is used in a FBAR sensor system which includes a sensor and a reference FBAR. The sensor signal is processed and a digital output representing the sensor input is transmitted using a two wire serial interface. The architecture is entirely digital and benefits from scaling to advanced...
This work proposes a new time-domain integration method to realize Electrochemical Impedance Spectroscopy (EIS). Unlike traditional EIS systems which use a quadrature sinusoid stimulus, we propose a low-frequency, low-amplitude sinusoid stimulus, which is realized through a sinusoid DAC without the need for analog filter. The error caused by harmonic generation can be suppressed through integration...
Electrocorticography (ECoG) has spectral characteristics that allow for possible efficiency improvements over traditional broadband recording of low frequency (1–150 Hz) data. In this paper we propose a spectrum-equalization technique for ECoG recording that can potentially decrease the dynamic range requirements of digitization by more than two orders of magnitude, corresponding to more than 6 bits...
We present a batteryless, 27uW barely subcutaneous sensing platform using optical power and data links. We demonstrate an 8.1 mm × 3.2 mm implantable tag powered by an 850nm infrared source through the skin barrier. Measurements using pig skin indicate that optical power transfer through skin achieves a 4.9% efficiency, which is higher than mm scale inductive power links. As a proof-of-concept demo,...
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