Showing papers on "Relaxation oscillator published in 2016"

A low frequency oscillator using a super-capacitor

Abstract: A low frequency relaxation oscillator is designed using a super-capacitor. An accurate analytical expression for the oscillation frequency is derived based on a fractional-order super-capacitor model composed of a resistance in series with a Constant Phase Element (CPE) whose pseudo-capacitance and dispersion coefficient are determined using impedance spectroscopy measurements. Experimental results confirm our theoretical analysis.

A 110 nW Resistive Frequency Locked On-Chip Oscillator with 34.3 ppm/°C Temperature Stability for System-on-Chip Designs

Abstract: This work presents a sub- $\mu \text {W}$ on-chip oscillator for fully integrated system-on-chip designs. The proposed oscillator introduces a resistive frequency locked loop topology for accurate clock generation. In this topology, a switched-capacitor circuit is controlled by an internal voltage-controlled oscillator (VCO), and the equivalent resistance of this switched-capacitor is matched to a temperature-compensated on-chip resistor using an ultra-low power amplifier. This design yields a temperature-compensated frequency from the internal VCO. The approach eliminates the traditional comparator from the oscillation loop; this comparator typically consumes a significant portion of the total oscillator power and limits temperature stability in conventional RC relaxation oscillators due to its temperature-dependent delay. A test chip is fabricated in $0.18~\mu \text {m}$ CMOS that exhibits a temperature coefficient of 34.3 ppm/°C with long-term stability of less than 7 ppm (12 second integration time) while consuming 110 nW at 70.4 kHz. A radio transmitter circuit that uses the proposed oscillator as a baseband timing source is also presented to demonstrate a system-on-chip design using this oscillator.

Ultra Low-Energy Relaxation Oscillator With 230 fJ/cycle Efficiency

Abstract: An ultra low-energy oscillator circuit is presented for use in picowatt level systems. The core oscillator uses an 18 transistor 3 stage architecture designed to minimize short circuit current. In addition, a transistor threshold is used to set the trip point as opposed to a voltage reference and comparator scheme, leading to overall energy savings. While operating across a wide range of low frequencies from 18 to 1000 Hz, the oscillator core consumes 110 fJ/cycle at 0.6 V. The circuit is demonstrated alongside an integrated current source to set the reference frequency. The combined system consumes a total power of 4.2 pW at 18 Hz, resulting in 230 fJ/cycle at 0.6 V.

Synchronization of two memristively coupled van der Pol oscillators

Abstract: The objective of this letter is to convey two essential principles of biological computing—synchronization and memory—in an electronic circuit with two van der Pol (vdP) oscillators coupled via a memristive device. The coupling was mediated by connecting the gate terminals of two programmable unijunction transistors through a resistance-capacitancenetwork comprising an Ag-TiOx-Al memristive device. In the high resistance state the memristance was in the order of MΩ, which leads to two independent self-sustained oscillators characterized by the different frequencies f1 and f2 and no phase relation between the oscillations. Depending on the mediated pulse amplitude, the memristive device switched to the low resistance state after a few cycles and a frequency adaptation and phase locking were observed. The experimental results are underlined by theoretically considering a system of two coupled vdP equations. This experiment may pave the way to larger neuromorphic networks in which the coupling parameters (through memristive devices) can vary in time and strength and are able to remember the history of applied electrical potentials.

A 12.77-MHz 31 ppm/°C On-Chip RC Relaxation Oscillator With Digital Compensation Technique

Abstract: The design of a 12.77-MHz on-chip RC relaxation oscillator with digital compensation technique is presented. To maintain the frequency stability versus temperature and supply voltage variations, loop delay tuning by a digital feedback loop is developed in this system. In order to generate an on-chip reference for digital calibration, a replica comparator is added. The on-chip relaxation oscillator is fabricated in 0.18- $\mu\text{m}$ CMOS process. The measured output frequency variation is 31 ppm/°C across −30 to 120 °C temperature range after compensation. The frequency variation over the supply voltage from 0.6 V to 1.1 V is ±0.5%/V. The measured total power consumption is 56.2 $\mu\text{W}$ at 0.9-V supply voltage when the digital compensation blocks are enabled. After digital compensation, the compensation blocks can be shutdown for power saving, and the main oscillator consumes only 12.8 $\mu\text{W}$ .

Fast equilibrium switch of a micro mechanical oscillator

Abstract: We demonstrate an accurate method to control the motion of a micromechanical oscillator in contact with a thermal bath. The experiment is carried out on the cantilever tip of an atomic force microscope. Applying an appropriate time dependent external force, we decrease the time necessary to reach equilibrium by two orders of magnitude compared to the intrinsic equilibration time. Finally, we analyze the energetic cost of such a fast equilibration, by measuring with kB T accuracy the energy exchanges along the process.

Ultra low power coupled oscillator arrays for computer vision applications

Abstract: Coupled oscillators provide an efficient non-Boolean paradigm for solving a variety of computationally intensive problems in computer vision. This motivates the realization of large networks of low-power coupled oscillators. In this work, we experimentally demonstrate: (i) a relaxation oscillator based on the insulator-metal transition (IMT) in vanadium dioxide (VO 2 ) with record low DC input (peak) power of ∼23 µW; (ii) a network of coupled VO 2 oscillators with record number of elements (6 oscillators) which perform image processing functionalities in high dimensional space like color detection and morphological operations such as dilation and erosion). Calibrated simulations show that 10× reduction in power compared to a 32 nm CMOS accelerator at iso-throughput.

5.10 A 1.4V 10.5MHz swing-boosted differential relaxation oscillator with 162.1dBc/Hz FOM and 9.86psrms period jitter in 0.18µm CMOS

Abstract: Relaxation oscillators have a profound scope as on-chip reference clock sources or sensor front-ends in comparison to ring oscillators due to their superior frequency stability, control linearity, and wide tuning range. However, despite a better fundamental limit predicted in theory, the phase noise performance of relaxation oscillators trails behind that of ring oscillators. Furthermore, there is a huge gap between the maximum achievable 1/f2 phase noise FOM (169dBc/Hz) [1] and those achieved by recently proposed low-power relaxation oscillator implementations [1–4].

An Oscillator-Based Active Bridge Circuit for Interfacing Capacitive Sensors With Microcontroller Compatibility

Abstract: This paper deals with the development of a signal conditioning circuit, with microcontroller compatibility, for interfacing capacitive sensors suitable for a wide range of applications. The circuit comprises of a capacitive active bridge, along with a relaxation oscillator for converting capacitance changes into frequency directly. The design, analysis, and experimental results of the circuit and its application to a thin-film-based humidity sensor and a capacitive transducer for measurement of the dielectric constant of edible oil are reported. The experimental results confirm the theoretical values predicted. The frequency output of the circuit has been used to determine the response characteristics of the trace moisture sensor and the dielectric constants of the edible oils. Finally, the output frequency has been calibrated in terms of the trace moisture in parts per million (ppm), using commercial dew point meter (SHAW, U.K.). The accuracy of moisture measurement using custom designed capacitive sensor for the full-scale moisture range of 4–100 ppm, compared with the dew point meter (accuracy ±0.1%), is found to be nearly ±1% and the resolution is 1 ppm moisture. The circuit is less complex and is easy to integrate to application-specific integrated circuits in a standard CMOS technology with high sensitivity (selectable). It can be easily reproduced with the cheapest possible components, while achieving fairly good performance in terms of both accuracy and dynamic range.

Circuit device, oscillator, electronic apparatus, and vehicle

Abstract: A circuit device includes an oscillation signal generation circuit, a reference signal input terminal to which a reference signal is input, and an internal phase comparator that performs phase comparison between an input signal based on the oscillation signal and the reference signal. The oscillation signal generation circuit generates the oscillation signal using the frequency control data based on a result of the phase comparison from an external phase comparator which performs phase comparison between an input signal based on the oscillation signal and the reference signal in a first mode, and generates the oscillation signal using the frequency control data based on a result of the phase comparison from the internal phase comparator in a second mode.

A 13.5-MHz relaxation oscillator with ±0.5% temperature stability for RFID application

Abstract: This paper presents a 13.5-MHz low-power, RC on-chip relaxation oscillator with split-capacitor technique for RFID application. This oscillator implements only one comparator and one reference voltage to minimize power consumption and silicon area. A loop delay variation cancellation technique that employs an integrator loop and a split-capacitor architecture helps attained the temperature stability in the proposed oscillator. The proposed design is fabricated in 0.18-μm CMOS process. The relaxation oscillator consumes 48.8 μW at 1.8-V power supply. The measurement results show that the circuit can generate a stable frequency of 13.5 MHz. The output frequency variation is less than ±0.5% of temperature range from −30° C to 120° C, and the supply voltage variation coefficient is 0.5%/V across 1.5 V to 2.1V supply voltage.

The Van der Pol's mathematical model of the voltage-controlled oscillator based on a transistor structure with negative resistance

Abstract: The results of the mathematical modelling for the voltage-controlled oscillator based on a transistor structure with negative resistance are presented in this article. The generated oscillations with and without noise were described with the Van der Pol's model. The research was carried out for relaxation and oscillator modes of the generator.

A CCII-based relaxation oscillator as a versatile interface for resistive and capacitive sensors

Abstract: In this paper, a novel Current-Mode (CM) square/triangular wave oscillator, based on second generation current conveyor (CCII), operating as resistance/capacitance to time conversion is described. The proposed oscillator, which consists of two CCII as an active element, three grounded resistances and one capacitance found to be an effective alternate of voltage mode based interfaces for wide range capacitive and resistive sensors. The interface circuit was implemented with commercially available current feedback operational amplifier AD844 from Analog Devices and passive components. Experimental results confirmed the theoretical expectations, showing good linearity in wide oscillation frequency/period range, which can be independently adjusted through resistive or capacitive external passive components. Experimental measurement was also conducted on a fabricated capacitive humidity sensor to verify the real time application of the proposed interface circuit. The interface circuit has shown a good accuracy and linearity for wide variation in capacitance of humidity sensor.

A 51-nW 32.7-kHz CMOS relaxation oscillator with half-period pre-charge compensation scheme for ultra-low power systems

Abstract: This paper presents a temperature and supply voltage variation-tolerant CMOS relaxation oscillator which is suitable for ultra-low power systems. A low-power low-cost half-period pre-charge compensation scheme is proposed to eliminate influences of the delay of the comparator and the RS latch on the frequency stability of the relaxation oscillator. In a clock period consisting of four working stages including normal charge, discharge, pre-charge and hold stage, the threshold voltage of comparators is adjusted dynamically. A 32.7-kHz relaxation oscillator with the proposed half-period pre-charge compensation scheme is implemented in a TSMC 0.18-μm CMOS process, occupying a silicon area of 0.048 mm2. Simulation results show that the proposed relaxation oscillator consumes 51-nW at room temperature from 0.6-V power supply, and temperature stability of 43.1 ppm/°C from −55 °C to 125 °C and ±0.60% frequency variation with supply voltage from 0.5 V to 1.0 V are achieved.

A Resistance-to-Digital Converter possessing exceptional insensitivity to circuit parameters

Abstract: A new Resistance-to-Digital Converter (RDC) suitable for single element resistive sensors is presented in this paper. The proposed scheme is based on a relaxation oscillator circuit, which along with a timer-counter that measures the time intervals of oscillations, provides digital output proportional to the resistance of the sensor. In most of the existing RDCs, the output characteristic has gain, offset and non-linearity errors owing to various circuit parameters and their drift in the measurement unit. The output of the proposed RDC has a special nature, by the design of the measurement method, that it is not a function of the circuit parameters such as offset voltages and bias currents of the opamps and comparators used, gain of various units employed, ON-resistance of the switches, value or mismatch in the magnitudes of the reference voltages employed, etc. Such a scheme will be useful for high accuracy measurements, even in circumstances where the above-mentioned parameters may vary or drift, due to variation in the measurement environment, say, large variation in temperature. A prototype of the proposed RDC has been developed in the laboratory and the performance has been tested under various conditions. The output was found to be linear with a worst-case non-linearity of 0.06 % As expected, the sensitive of the output of the prototype RDC to various circuit parameters was found to be negligible.

Dual-Band Waveform Generator With Ultra-Wide Low-Frequency Tuning-Range

Abstract: This paper presents a novel mixed-signal low-power dual-band square/triangular waveform generator (WFG) chip with a wide low-frequency tuning range for medical bio-electric stimulation therapy. It consists of a relaxation oscillator comprising a hysteresis Schmitt trigger and a timing integrator, along with frequency divider (FD) stages and path selector output for driving an electrode from 16 selectable channels. It was fabricated using Global Foundries 8RF-DM 130-nm CMOS process with a supply voltage of ±1 V for the oscillator and +1 V for logic circuits. The WFG provides an output of around 1.5 $\text{V}_{\textrm {p-p}}$ at a nominal low oscillation frequency of 17 kHz using small-size on-chip passive components of values 10 $\text{k}\Omega $ and 10 pF. The WFG core (band I) can be tuned in the range 6.44–1003 kHz through bias current adjustment, while a lower frequency (band II) in the range 0.1 Hz–502 kHz can be provided digitally through a $\div 2$ stage. The power consumption was only 0.457 mW for the WFG and 2.1 mW for the FD circuit while occupying a total silicon area of only 18 $426~\mu \text{m}^{2}$ .

A PVT-tolerant relaxation oscillator in 65nm CMOS

Abstract: A fully-integrated CMOS relaxation oscillator (ROSC) using a process-voltage-temperature (PVT) insensitive current reference generator is presented. The oscillator is designed to generate a clock frequency of 64.4kHz in 65-nm CMOS technology for switched-capacitor circuit applications. The Monte-Carlo simulation results have shown that the ROSC is able to achieve 3.66% in the process sensitivity (σ/μ). The output frequency variation is 1.71% over the temperature range from −20°C to 100°C and 0.73% over the supply variation from 1.2V to 2V. The power consumption of ROSC is 4.32µW at 1.2V supply. It has displayed better figure-of merit (FOM) against PVT variations with respect to other reported prior-art works.

FM-UWB transmitter for wireless body area networks: Implementation and simulation

Abstract: This paper describes an implementation of low power frequency modulated ultra-wideband (FM-UWB) transmitter in standard 130nm CMOS technology. The transmitter is designed to operate in the range of 3.328–4.608 GHz. A relaxation oscillator is used to generate the subcarrier signal which is calibrated by a phase-locked loop (PLL). The RF carrier is generated using a voltage-controlled oscillator (VCO). A proposed calibration scheme based on a PLL is utilized to calibrate both the upper and the lower frequencies of the operation band. The proposed FM-UWB transmitter consumes 835μW from a 1.2V supply at 500kbps achieving an energy efficiency of 1.67nJ/bit.

An 143nW relaxation oscillator for ultra-low power biomedical systems

Abstract: This work presents a near zero power relaxation oscillator for biomedical applications. Relaxation oscillators have now become a potential candidate for on-chip clock references due to their miniaturized sizes and integrating capability. In order to be suitable for biomedical applications, accurate and energy-efficient oscillators are required. An ultra-low power relaxation oscillator with 20kHz oscillating frequency is implemented with 0.13μm CMOS process. A switched-current technique is proposed to reduce the power consumption without compromising the overall performance. The relaxation oscillator consumes 143nW power and has a temperature coefficient of 19.1ppm/° C with a phase noise of −93dBc/Hz at 1kHz offset frequency.

Computing with dynamical systems in the post-CMOS era

Abstract: In the pursuit for building hardware accelerators to compute optimization problems researchers realize that the challenges in achieving this objective lie not only in implementing the hardware but also in the formulating the computing fundamentals of such designs. Neural network algorithms are considered most suited for this task, as there is usually a direct description of distributed computing entities, called “neurons”, and their interactions which can be mapped to both electronic and non-electronic hardware. In this regard, coupled oscillator systems have been studied where individual oscillators correspond to neurons and the information is encoded in either phase or frequency. But as is the case with neural networks, the computational power of the network depends on complexity of interactions among oscillators, and it is a challenge to implement oscillator networks with complex simultaneous interactions among multiple oscillators. Sinusoidal oscillators with assumption of weak linear phase coupling, akin to Kumamoto models, have been studied in theory but implementing such oscillators with weak couplings and encoding information in phase or frequency have been a challenge. Examples of using novel devices for making neural network hardware include memristor based neuromorphic synapses [1] and spin-torque oscillator (STO) based systems [2]. In our work, we use relaxation oscillators coupled using passive elements — capacitances or resistances — without the assumption of weak linear phase couplings. Our theoretical models are derived from circuit implementations, instead of the other way round, which means there are only engineering challenges in implementing the hardware, and no modeling discrepancies. We have explored two kinds of implementations — (a) simple pairwise coupling scheme with information encoded as frequency for pattern matching and associative computing, and (b) complex global coupling with information encoded in phase for the NP-hard graph coloring problem. We have been demonstrated in theory, using simulations and experimental implementations using VO 2 devices, the working of such coupled relaxation oscillator networks.

Singularly perturbed phase response curves for relaxation oscillators

Abstract: We exploit a novel geometric method to construct the global isochrones of relaxation oscillators and the associated phase response curve. This method complements the classical infinitesimal (local) phase response curve approach by constructively predicting the finite phase response curve near the singular limit of infinite timescale separations between the oscillator variables. We illustrate the power of our construction on the FitzHugh-Nagumo model of neuronal spike generation. Because of its global and constructive nature, not requiring extensive numerical simulations, the proposed approach is particularly suited to control design applications.

Reactance-less RM relaxation oscillator using exponential memristor model

Abstract: Recently, the memristor based relaxation oscillators become an important topic in circuit theory where the reactive elements are replaced by memristor which occupies a very small area. In this paper, a design of memristor-based relaxation oscillator is introduced based on exponential memristor model. Unlike previously published oscillators which were built based on a simple memristor model, the exponential model is used, as a generalized model, to verify the concept of memristor based RM oscillator using a model that has electrical characteristic very close to the fabricated device. First, the effect of changing parameters of the memristor is illustrated using graphical analysis. Then, a reasonable range of values for the device parameters are selected to be suitable for the operation of the RM oscillator. The mathematical modeling of the memristor in the oscillator is introduced, in addition to the effect of changing the control voltage on the oscillation frequency. The design and simulations were carried out using Cadence Virtuoso.

Noise Spike Model in Relaxation Oscillators Based on Physical Phase Change

Abstract: A new approach to augment existing noise models in a relaxation oscillator by including noise spikes during state change, an important aspect hitherto not covered in existing noise models, is proposed. Such noise spike is due to regeneration at the jump and this paper attempts to offer an explanation by viewing state change as a physical phase change in a thermodynamic system, which is also due to regeneration. The connection is established by viewing the relaxation oscillator as a combination of bistable circuit (exhibits metastablility) and a timing capacitor. Similarly the thermodynamic system exhibits physical phase change (metastability). Formula is derived to predict the “magnitude” of the noise spike, as a function of regeneration parameter, and hence design parameter such as ${g}_{m}$ , $R$ , ${I}_{0}$ . Simulations (Eldo) on circuits and simulations (Metropolis) on thermodynamic system as well as measurements on circuits fabricated in 0.13 $\mu$ m CMOS technology are consistent with theory.

A low-power oscillator-based readout interface for medical ultrasonic sensors

Abstract: This paper proposed an oscillator-based ultrasonic sensor interface that can be applied to intravascular applications. The readout circuits are validated with a capacitive micromachined ultrasonic transducer (CMUT) and a current-to-frequency chip. The CMOS CMUTs are integrated with a current amplifier on the same chip and the current-to-frequency chip provides the current-to-frequency readout interface. Relaxation oscillators with injection locking are employed to achieve low-power consumption. Also, the time-based output signal can be further digitized with a time-to-digital converter. Both chips are fabricated in a 0.35μm CMOS MEMS process technology. The CMUTs are designed with 1MHz to 4MHz cells for intravascular diagnosis applications. The current amplifier consumes 281.7 μW and the power consumption of the current-to-frequency circuits is 25.4 μW.

Relaxation oscillator and monolithic integrated chip

Abstract: The invention provides a relaxation oscillator and a monolithic integrated chip. The relaxation oscillator comprises a relaxation oscillator circuit, and the relaxation oscillator circuit comprises a threshold voltage generating circuit, a capacitance charging and discharging circuit and a comparator circuit, wherein the threshold voltage generating circuit inputs a threshold voltage signal to an inverting input end of the comparator circuit; the capacitance charging and discharging circuit inputs capacitance voltage signals to an in-phase input end and an inverting input end of the comparator circuit; the threshold voltage generating circuit comprises a first current source, a second current source and a threshold resistance, the first current source supplies current to the threshold resistance through a first inverter switch element, and the second current source extracts the current from the threshold resistance through a first in-phase switch element; and the capacitance charging and discharging circuit comprises a third current source, a fourth current source and a capacitor, the third current source supplies the current to the capacitor through a second inverter switch element, and the fourth current source extracts the current from the capacitor through a second in-phase switch element. The monolithic integrated chip provided by the invention can be applied to the relaxation oscillator.

High-level simulation of an FSK modulator based on memconductor

Abstract: This paper deals with the high-level simulation of a frequency-shift-keying (FSK) modulator based on charge-controlled memconductor. The behavioral model of the memconductor is built on SIMULINK under MATLAB environment. It is demonstrated that the incremental memconductance increases and decreases according the width and amplitude of a positive and negative pulse signal, respectively; whereas the decremental memconductance increases and decreases according the width and amplitude of a negative and positive pulse signal. Both incremental and decremental memconductances are used to on-line reconfigure the frequency of oscillation of a single-memconductor controlled oscillator configured as FSK modulator. The obtained results not only allows an easy reconfigurability of the FSK modulator, but also demonstrate the viability of the memconductor to be used in other applications such as cellular neural networks, controllers, sensors, chaotic systems, relaxation oscillators, nonvolatile memory devices and programmable analog circuits.

A 150nW 32 kHz mobility-compensated relaxation oscillator with +/−30ppm/°C temperature stability

Abstract: A relaxation oscillator is presented that makes use of a current-mode Schmitt trigger to reduce the effects of process, voltage and temperature (PVT) variations. A detailed analysis of the oscillator, including the temperature performance, is presented and verified by experimental results. A test chip with a typical frequency of 32 kHz was fabricated in a 0.18 μm standard CMOS process. The measured frequency variations were +/− 30 ppm/°C for temperature variation from −20 °C to 80°C and +/− 500 ppm/V for supply voltage variation from 0.7 V to 1.8 V. The short term stability is 66 ppm (2 ns) of jitter while the long term stability is 500 ppm of Allan deviation after 10 seconds. A careful design results in a total area of 0.1 mm2 and a power consumption of 150 nW.

Voltage-controlled M-M relaxation oscillator

Abstract: This paper discusses voltage-controlled M-M relaxation oscillator with analytical and circuit simulations. The introduced circuit has two different configurations based on the polarities of memristor; whether they are in the same direction or in the opposite direction. The Analytical formulas are function of the reference voltage such as the oscillation frequency and oscillation conditions for each case are derived with some numerical examples. The circuit simulations are introduced to validate the mathematical concepts as well as the effect of the reference voltage which can be used in frequency modulation application. A comparison between the two oscillators is presented versus different parameters. Finally, similar discussion based on asymmetric voltage controlled oscillator is introduced where different frequency ranges can be obtained.