Neuromorphic VLSi

—This work proposes a low power digital block for spatial localization of sensors within the limited area/power budget of sensor nodes. We show a novel digital architecture for a Linear Program (LP) solver based on a recurrent (non-linear feedback) Neural Network (RNN). Training data is not needed in our approach. We solve the primal and dual optimization problems for spatial localization with a single multi-functional data path which does not require matrix inversions. FPGA and ASIC implementations are presented which target a sensor (microrobot) localization problem in 2D using angle-of-arrival (AOA) measurements. The results show that the estimated locations (2D coordinates) are very close to the ground truth values in all tested scenarios. The proposed RNN has input and output layers, and a hidden layer with four neurons. FPGA implementation of the localizer in 180 nm process dissipates 180 mW of power at 1.5V and 31.25 MHz. When scaled to 128 neurons the performance is 13 Mop/sec/W for the same FPGA technology. The design has been also simulated in an ASIC 45 nm (PDK45 1V VDD) standard cell technology. With 128 neurons in the hidden layer the ASIC consumes 196.9 mW power at 516 MHz, which is equivalent to 677.165 Mop/sec/W. The proposed design significantly improves computing efficiency over the recently published results for similar implementations.

This paper presents comparative study of high-speed, low-power and low voltage full adder circuits. Our approach is based on XOR-XNOR design full adder circuits in a single unit. A low power and high performance 9T full adder cell using a design style called " XOR (3T) " is discussed. The designed circuit commands a high degree of regularity and symmetric higher density than the conventional CMOS design style as well as it lowers power consumption by using XOR (3T) logic circuits. Gate Diffusion Input (GDI) technique of low-power digital combinatorial circuit design is also described. This technique helps in reducing the power consumption and the area of digital circuits while maintaining low complexity of logic design. This paper analyses, evaluates and compares the performance of various adder circuits. Several simulations conducted using different voltage supplies, load capacitors and temperature variation demonstrate the superiority of the XOR (3T) based full adder designs in term of delay, power and power delay product (PDP) compared to the other full adder circuits. Simulation results illustrate the superiority of the designed adder circuits against the conventional CMOS, TG and Hybrid full adder circuits in terms of power, delay and power delay product (PDP). .

The ability to carry out signal processing, classification, recognition, and computation in artificial spiking neural networks (SNNs) is mediated by their synapses. In particular, through activity-dependent alteration of their efficacies, synapses play a fundamental role in learning. The mathematical prescriptions under which synapses modify their weights are termed synaptic plasticity rules. These learning rules can be based on abstract computational neuroscience models or on detailed biophysical ones. As these rules are being proposed and developed by experimental and computational neuroscientists, engineers strive to design and implement them in silicon and en masse in order to employ them in complex real-world applications. In this paper, we describe analog very large-scale integration (VLSI) circuit implementations of multiple synaptic plasticity rules, ranging from phenomenological ones (e.g., based on spike timing, mean firing rates, or both) to biophysically realistic ones (e.g., calcium-dependent models). We discuss the application domains, weaknesses, and strengths of various representative approaches proposed in the literature , and provide insight into the challenges that engineers face when designing and implementing synaptic plasticity rules in VLSI technology for utilizing them in real-world applications.

Communication systems use the concept of transmitting information using the electrical distribution network as a communication channel. To enable the transmission data signal modulated on a carrier signal is superimposed on the electrical wires. Typical power lines are designed to handle 50/60 Hz of AC power signal; however they can carry the signals up to 500 KHz frequency. This work aims to aid transmission/reception of an audio signal in the spectrum from 300 Hz to 4000 Hz using PLCC on a tunable carrier frequency in the spectrum from 200 KHz to 500 KHz. For digital amplitude modulation the sampling rate of the carrier and the audio signal has to be matched. Tunable carrier generation can be achieved with Direct Digital Synthesizers at a desired sampling rate. DSP Sample rate conversion techniques are very useful to make the sampling circuits to work on their own sampling rates which are fine for the data/modulated-carrier signal's bandwidth. This also simplifies the complexity of the sampling circuits. Digital Up Conversion (DUC) and Digital Down Conversion (DDC) are DSP sample rate conversion techniques which refer to increasing and decreasing the sampling rate of a signal respectively. The objective was to design and implement low power ASIC of DUC and DDC designs at 65nm for PLCC. Low power implementation was carried out using Multi-VDD technique. MATLAB software models were used to understand the DUC and DDC designs. RTL to GDS flow was executed using Synopsys tools such as VCS, Design Compiler, IC Compiler and PrimeTime. Key milestones of this activity are RTL verification, synthesis, gate-level simulations, low power architecture definitions, physical implementation, ASIC signoff checks and postroute delay based simulations. Multi-VDD technique deployed on DUC and DDC helped to reduce the power consumption from 280.9uW to 198.07uW and from 176.26uW to 124.47uW respectively. DUC and DUC designs have met functionality at 64MHz clock frequency. Both the designs have passed postroute delay based simulations, static performance checks, power domain checks and TSMC's 65nm design rule checks.

A significant portion of the total power consumption in high performance digital circuits in deep sub-micron regime is mainly due to leakage power. Leakage is the only source of power consumption in an idle circuit. Therefore it is important to reduce leakage power in portable systems. In this paper two techniques such as transistor stacking and self-adjustable voltage level circuit for reducing leakage power in sequential circuits are proposed. This work analyses the power and delay of three different types of D flip-flops using pass transistors, transmission gates and gate diffusion input gates.. All the circuits are simulated with and without the application of leakage reduction techniques. Simulation results show that the proposed pass transistor based D flip-flop using self-adjustable voltage level circuit has the least leakage power dissipation of 9.13nW with a delay of 77 nS. The circuits are simulated with MOSFET models of level 54 using HSPICE in 90 nm process technology.

In this paper, we propose a new multiplier-and-accumulator (MAC) architecture for low power and high speed arithmetic. High speed and low power MAC units are required for applications of digital signal processing like Fast Fourier Transform, Finite Impulse Response filters, convolution etc. For improving the speed and reducing the dynamic power, there is a need to reduce the glitches (1 to 0 transition) and spikes (0 to 1 transition). Adder designed using spurious power suppression technique (SPST) avoids the unwanted glitches and spikes, thus minimizing the switching power dissipation and hence the dynamic power. Radix-2 modified booth algorithm reduces the number of partial products to half by grouping of bits from the multiplier term, which improves the speed. The proposed radix-2 modified Booth algorithm MAC with SPST gives a factor of 5 less delay and 7% less power consumption as compared to array MAC. KEYWORDS Radix-2 modified booth algorithm, Digital signal processing, spurious power suppression Technique, Verilog.

Pulse compression technique is most widely used in radar and communication areas. Its implementation requires an optimized and dedicated hardware. The real time implementation places several constraints such as area occupied, power consumption , etc. The good design needs optimization of these constraints. This paper concentrates on the design of optimized model which can reduce these. In the proposed architecture a single chip is used for generating the pulse compression sequence like BPSk, QPSk, 6-PSK and other Polyphase codes. The VLSI architecture is implemented on the Field Programm-able Gate Array (FPGA) as it provides the flexibility of reconfigurability and reprogrammability .It was found that the proposed architecture has generated the pulse compression sequences efficiently while improving some of the parameters like area, power consumption and delay when compared to previous methods.

International Journal of Embedded Systems and Applications (IJESA) is a quarterly open access peer-reviewed journal that publishes articles which contribute new results in all areas of the Embedded Systems and applications. The goal of this journal is to bring together researchers and practitioners from academia and industry to focus on understanding Embedded Systems and establishing new collaborations in these areas.

This paper presents the design of high-speed full adder circuits using a new CMOS mixed mode logic family. The objective of this work is to present a new full adder design circuits combined with current mode circuit in one unit to implement a full adder cell. This paper also discusses a high-speed hybrid majority function based 1-bit full adder that uses MOS capacitors (MOSCAP) in its structure with conventional static and dynamic CMOS logic circuit. The static Majority function (bridge) design style enjoys a high degree of regularity and symmetric higher density than the conventional CMOS design style as well as lower power consumption by using bridge transistors. This technique helps in reducing power consumption, propagation delay, and area of digital circuits while maintaining low complexity of mixed-mode logic designs. Dynamic CMOS circuits enjoy area, delay and testability advantages over static CMOS circuits. Simulation results illustrate the superiority of the new designed adder circuits against the reported conventional CMOS, dynamic and majority function adder circuits, in terms of power, delay, power delay product (PDP) and energy delay product (EDP). The design is implemented on UMC 0.18µm process models in Cadence Virtuoso Schematic Composer at 1.8 V single ended supply voltage and simulations are carried out on Spectre S.. KEYWORDS Full adder, Majority-Not gate, Dynamic circuits, MOSCAP, Power-delay product (PDP), Very Large Scale Integrated (VLSI) Circuits, Current mode logic, Hybrid XOR-XNOR circuit, Bridge full adder.

D stacking is a promising technology (low latency/power/area, high bandwidth); its main shortcoming is increased power density. Simultaneously, motivated by energy constraints, architectures are evolving towards greater customization, with tasks delegated to ac- celerators. Due to the widespread use of machine-learning algo- rithms and the re-emergence of neural networks (NNs) as the pre- ferred such algorithms, NN accelerators are receiving increased at- tention. They turn out to be well matched to 3D stacking: inherently 3D structures with a low power density and high across-layer band- width requirements. We present what is, to the best of our knowl- edge, the first 3D stacked NN accelerator

The performance factors such as propagation delay, power dissipation and crosstalk in RC modelled interconnects are major design issues for the System on-chip (SoC) designs in current Deep Submicron (DSM) era. The crosstalk effect is a consequence of coupling and switching activities that is encountered when there is a transition as compared to previous state of wire and or when there are transitions in adjacent wires. Therefore, minimization or elimination of switching and coupling activities is crucial in enhancing the performance of SoC designs. There are several methods for the reduction of power dissipation, crosstalk and delay. The encoding method is most effective and popular method for enhancing the behaviour of on-chip buses. This paper proposes encoding scheme to achieve overall reduction in transitions. The reduction in transition improves the performance in terms of reduced power dissipation, coupling activity and delay in on-chip buses. This encoding method is implemented using VHDL. The result evidently demonstrates reduction in transitions which consequently improves the overall performance of on-chip buses.

In this paper, a new five-transistor (5T) single-port Static Random Access Memory (SRAM) cell with voltage assist is proposed. Amongst them, a word line suppression circuit is designed to provide a voltage of the respective connected word line signal in a selected row cells lower than the power supply voltage V DD by a threshold voltage during a read operation, thereby to improve the read/write-ability of the cell. In addition, a voltage control circuit is coupled to the sources corresponding to driver transistors of each row memory cells. This configuration is aimed to control the source voltages of driver transistors under different operating modes. Specifically, during a read operation, a two-stage reading mechanism is engaged to increase the reading speed. Simulation results for the proposed cell design confirm that there is a conspicuous improvement in reading speed and power saving over the conventional SRAM cells, and fast writing also can be achieved.

Analog-to-digital converters (ADCs) are key design blocks and are currently adopted in many application fields to improve digital systems, which achieve superior performances with respect to analog solutions. Application such as wireless communication and digital audio and video have created the need for cost-effective data converters that will achieve higher speed and resolution. Widespread usage confers great importance to the design activities, which nowadays largely contributes to the production cost in integrated circuit devices (ICs). Various examples of ADC applications can be found in data acquisition systems, measurement systems and digital communication systems also imaging, instrumentation systems. Since the ADC has a continuous, infinite –valued signal as its input, the important analog points on the transfer curve x-axis for an ADC are the ones that corresponding to changes in the digital output word. These input transitions determine the amount of INL and DNL associated with the converter. Hence, we have to considered all the parameters and improving the associated performance may significantly reduce the industrial cost of an ADC manufacturing process and improved the resolution and design specially power consumption. The paper presents a design of 4 bit Pipeline ADC with low power dissipation implemented in <0.18µm.

Conventionally polysilicon is used in MOSFETs for gate material. Doping of polysilicon and thus changing the workfunction is carried out to change the threshold voltage. Additionally polysilicon is not favourable as gate material for smaller dimensional devices because of its high thermal budget process and degradation due to the depletion of the doped polysilicon, thus metal gate is preferred over polysilicon. Control of workfunction in metal gate is a challenging task. The use of metal alloys as gate materials for variable gate workfunction has been already reported in literature. In this work various threshold voltage techniques has been analyzed and a novel aligned dual metal gate technique is proposed for threshold voltage control in FinFETs.

This paper deals with the design and analysis of high speed Static Random Access Memory (SRAM) cell and Dynamic Random Access Memory (DRAM) cell to develop low power consumption. SRAM and DRAM cells have been the predominant technologies used to implement memory cells in computer systems, each one having its advantages and shortcomings. SRAM cells are faster and require no refresh since reads are not destructive. In contrast, DRAM cells provide higher density and minimal leakage energy. Here we use 12-transistor SRAM cell built from a simple static latch and tri state inverter. The reading action itself refreshes the content of memory. The SRAM access path is split into two portions: from address input to word line rise (the row decoder) and from word line rise to data output (the read data path). The decoder which constitutes the path from address input to the word line rise is implemented as a binary structure by implementing a multi-stage path. The key to low power operation in the SRAM data path is to reduce the signal swings on the high capacitance nodes like the bit lines and the data lines.

Communication systems use the concept of transmitting information using the electrical distribution network as a communication channel. To enable the transmission data signal modulated on a carrier signal is superimposed on the electrical wires. Typical power lines are designed to handle 50/60 Hz of AC power signal; however they can carry the signals up to 500 KHz frequency. This work aims to aid transmission/reception of an audio signal in the spectrum from 300 Hz to 4000 Hz using PLCC on a tunable carrier frequency in the spectrum from 200 KHz to 500 KHz. For digital amplitude modulation the sampling rate of the carrier and the audio signal has to be matched. Tunable carrier generation can be achieved with Direct Digital Synthesizers at a desired sampling rate. DSP Sample rate conversion techniques are very useful to make the sampling circuits to work on their own sampling rates which are fine for the data/modulated-carrier signal's bandwidth. This also simplifies the complexity of the sampling circuits. Digital Up Conversion (DUC) and Digital Down Conversion (DDC) are DSP sample rate conversion techniques which refer to increasing and decreasing the sampling rate of a signal respectively. The objective was to design and implement low power ASIC of DUC and DDC designs at 65nm for PLCC. Low power implementation was carried out using Multi-VDD technique. MATLAB software models were used to understand the DUC and DDC designs. RTL to GDS flow was executed using Synopsys tools such as VCS, Design Compiler, IC Compiler and PrimeTime. Key milestones of this activity are RTL verification, synthesis, gate-level simulations, low power architecture definitions, physical implementation, ASIC signoff checks and postroute delay based simulations. Multi-VDD technique deployed on DUC and DDC helped to reduce the power consumption from 280.9uW to 198.07uW and from 176.26uW to 124.47uW respectively. DUC and DUC designs have met functionality at 64MHz clock frequency. Both the designs have passed postroute delay based simulations, static performance checks, power domain checks and TSMC's 65nm design rule checks.

In this paper we present a novel switched-capacitor implementation of short-term synaptic dynamics with simultaneous depression and facilitation. The developed circuit model is a modified version of a model of neurotransmitter release derived from biological measurements. Despite the simplicity of the circuit the rich dynamics of the original model can be delivered. By completely relying on SC techniques for all calculations, our circuit is significantly less sensitive to process variations and easier to calibrate than commonly employed subthreshold circuits. The circuit makes use of a technique for minimizing leakage effects allowing for real-time operation with time constants up to several seconds. Functionality and robustness of the circuit are verified by simulations and comparisons to the original model.

In this paper two novel high performance designs for AND and OR basic gates and a novel Full-Adder Cell are presented. These designs are based on carbon nanotube technology. In order to compare the proposed designs with previous ones both MOSFET based and CNFET based circuits are selected. By the way the proposed designs have better performance in comparison with previous designs in terms of speed, power consumption and power-delay product (PDP).

Fault diagnosis in processing digital system application has raised various limiting problems. While basic objective of fault tolerant systems is to minimize the fault occurring in the device, the processing error is an additional error to be considered. Past approaches were observed to be focusing much on internal fault in digital device, the error due to processing and communication is to be developed. In this paper a self correcting approach to memory design based on memory interface is proposed. The error approach observed in case of forwarding binary data to encode, store and retrieve with error free coding is proposed. The Process of memory error free coding results in higher reliability in case of bit and block coding.

The architectural and circuit design aspects of a mixed analog/digital very large scale integration (VLSI) motion detection chip based on models of the insect visual system are described. The chip comprises two one-dimensional 64-cell arrays as well as front-end analog circuitry for early visual processing and digital control circuits. Each analog processing cell comprises a photodetector, circuits for spatial averaging and multiplicative noise cancellation, differentiation, and thresholding. The operation and configuration of the analog cells is controlled by digital circuits, thus implementing a reconfigurable architecture which facilitates the evaluation of several newly designed analog circuits. The chip has been designed and fabricated in a 1.2-m CMOS process and occupies an area of 2 x 2 mm^2 .

Neuromorphic circuits are becoming quite popular due to their ability to mimic the structure and behavior of human brain. Current research focuses on approximating spiking biological neuron behavior. Various neuron models have been proposed in the past that aid in investigating the behavior of neuronal systems mathematically. Mihalas-Niebur (MN) neuron model is one among them. In this paper log-domain based MN neuron model is implemented at 45 nm technology node. The paper studies the effects of process-temperature variations and also investigates the impact of Hot Carrier Injection (HCI), Bias Temperature Instability (BTI) on the performance of MN circuit. Average power consumption and spiking frequency are chosen as key performance measures to analyze the circuit performance before and after degradation.

The computational function of neural networks is thought to depend primarily on the learning/plasticity function carried out at the synapse. Neuromorphic circuit realizations have taken this into account by implementing a variety of synaptical processing functions, with most recent synapse circuits replicating some form of Spike Time Dependent Plasticity (STDP). However, STDP is being challenged by older rate-dependent learning rules as well as by biological experiments exhibiting more complex timing rules (e.g. spike triplets) as well as simultaneous rate- and timing dependent plasticity. In this paper, we present a circuit realization of a plasticity rule based on the postsynaptic neuron potential as well as the transmission profile of the presynaptic spike. To the best of our knowledge, this is the first circuit realization of synaptical behaviour which moves significantly beyond STDP, replicating the triplet experiments of Froemke and Dan, the combined timing and rate experiments of Sjoestroem et al., as well as conventional BCM behaviour.

Neuromorphic circuits are becoming quite popular due to their ability to mimic the structure and behavior of human brain. Current research focuses on approximating spiking biological neuron behavior. Various neuron models have been proposed in the past that aid in investigating the behavior of neuronal systems mathematically. Mihalas-Niebur (MN) neuron model is one among them. In this paper log-domain based MN neuron model is implemented at 45 nm technology node. The paper studies the effects of process-temperature variations and also investigates the impact of Hot Carrier Injection (HCI), Bias Temperature Instability (BTI) on the performance of MN circuit. Average power consumption and spiking frequency are chosen as key performance measures to analyze the circuit performance before and after degradation.