Analog and Mixed Signal Verification

More and more electronic systems have components that are not purely digital. Verification of such systems is a much less developed discipline than the digital equivalents and the application of formal (mathematically complete) techniques is a nascent area. In this paper, we will discuss the nature of analog circuit design and describe the way verification is done in practice today. We will describe some “formal” approaches coming from the analog design community. We will describe some of the approaches to formal verification that have been presented in recent literature. Finally, we will mention some areas where there are opportunities for future work

Testing microelectronic biofluidic systems

According to the 2005 International Technology Roadmap for Semiconductors, the integration of emerging nondigital CMOS technologies will require radically different test methods, posing a major challenge for designers and test engineers. One such technology is microelectronic fluidic (MEF) arrays, which have rapidly gained importance in many biological, pharmaceutical, and industrial applications. The advantages of these systems, such as operation speed, use of very small amounts of liquid, on-board droplet detection, signal conditioning, and vast digital signal processing, make them very promising. However, testable design of these devices in a mass-production environment is still in its infancy, hampering their low-cost introduction to the market. This article describes analog and digital MEF design and testing method

Analog Defect Injection and Fault Simulation Techniques: A Systematic Literature Review

Since the last century, the exponential growth of the semiconductor industry has led to the creation of tiny and complex integrated circuits, e.g., sensors, actuators, and smart power. Innovative techniques are needed to ensure the correct functionality of analog devices that are ubiquitous in every smart system. The ISO 26262 standard for functional safety in the automotive context specifies that fault injection is necessary to validate all electronic devices. For decades, standardization of defect modeling and injection mainly focused on digital circuits and, in a minor part, on analog ones. An initial attempt is being made with the IEEE P2427 draft standard that started to give a structured and formal organization to the analog testing field. Various methods have been proposed in the literature to speed up the fault simulation of the defect universe for an analog circuit. A more limited number of papers seek to reduce the overall simulation time by reducing the number of defects to be simulated. This literature survey describes the state-of-the-art of analog defect injection and fault simulation methods. The survey is based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodological flow, allowing for a systematic and complete literature survey. Each selected paper has been categorized and presented to provide an overview of all the available approaches. In addition, the limitations of the various approaches are discussed by showing possible future directions

Towards more Dependable Verification of Mixed-Signal Systems

The verification of complex mixed-signal systems is a challenge, especially considering the impact of parameter variations. Besides the established approaches like Monte-Carlo or Corner-Case simulation, a novel semi-symbolic approach emerged in recent years. In this approach, parameter variations and tolerances are maintained as symbolic ranges during numerical simulation runs by using affine arithmetic. Maintaining parameter variations and tolerances in a symbolic way significantly increases verification coverage. In the following we give a brief introduction and an overview of research on semi-symbolic simulation of both circuits and systems and discuss possible application for system level verification and optimization

Fault-based Analysis of Industrial Cyber-Physical Systems

The fourth industrial revolution called Industry 4.0 tries to bridge the gap between traditional Electronic Design Automation (EDA) technologies and the necessity of innovating in many indus- trial fields, e.g., automotive, avionic, and manufacturing. This complex digitalization process in- volves every industrial facility and comprises the transformation of methodologies, techniques, and tools to improve the efficiency of every industrial process. The enhancement of functional safety in Industry 4.0 applications needs to exploit the studies related to model-based and data-driven anal- yses of the deployed Industrial Cyber-Physical System (ICPS). Modeling an ICPS is possible at different abstraction levels, relying on the physical details included in the model and necessary to describe specific system behaviors. However, it is extremely complicated because an ICPS is com- posed of heterogeneous components related to different physical domains, e.g., digital, electrical, and mechanical. In addition, it is also necessary to consider not only nominal behaviors but even faulty behaviors to perform more specific analyses, e.g., predictive maintenance of specific assets. Nevertheless, these faulty data are usually not present or not available directly from the industrial machinery. To overcome these limitations, constructing a virtual model of an ICPS extended with different classes of faults enables the characterization of faulty behaviors of the system influenced by different faults. In literature, these topics are addressed with non-uniformly approaches and with the absence of standardized and automatic methodologies for describing and simulating faults in the different domains composing an ICPS. This thesis attempts to overcome these state-of-the-art gaps by proposing novel methodologies, techniques, and tools to: model and simulate analog and multi-domain systems; abstract low-level models to higher-level behavioral models; and monitor industrial systems based on the Industrial Internet of Things (IIOT) paradigm. Specifically, the proposed contributions involve the exten- sion of state-of-the-art fault injection practices to improve the ICPSs safety, the development of frameworks for safety operations automatization, and the definition of a monitoring framework for ICPSs. Overall, fault injection in analog and digital models is the state of the practice to en- sure functional safety, as mentioned in the ISO 26262 standard specific for the automotive field. Starting from state-of-the-art defects defined for analog descriptions, new defects are proposed to enhance the IEEE P2427 draft standard for analog defect modeling and coverage. Moreover, dif- ferent techniques to abstract a transistor-level model to a behavioral model are proposed to speed up the simulation of faulty circuits. Therefore, unlike the electrical domain, there is no extensive use of fault injection techniques in the mechanical one. Thus, extending the fault injection to the mechanical and thermal fields allows for supporting the definition and evaluation of more reliable safety mechanisms. Hence, a taxonomy of mechanical faults is derived from the electrical domain by exploiting the physical analogies. Furthermore, specific tools are built for automatically instru- menting different descriptions with multi-domain faults. The entire work is proposed as a basis for supporting the creation of increasingly resilient and secure ICPS that need to preserve functional safety in any operating context

Modeling and simulation of magnetic components in electric circuits

This thesis demonstrates how by using a variety of model constructions and parameter extraction techniques, a range of magnetic component models can be developed for a wide range of application areas, with different levels of accuracy appropriate for the simulation required. Novel parameter extraction and model optimization methods are developed, including the innovative use of Genetic Algorithms and Metrics, to ensure the accuracy of the material models used. Multiple domain modeling, including the magnetic, thermal and magnetic aspects are applied in integrated simulations to ensure correct and complete dynamic behaviour under a range of environmental conditions. Improvements to the original Jiles-Atherton theory to more accurately model loop closure and dynamic thermal behaviour are proposed, developed and tested against measured results. Magnetic Component modeling techniques are reviewed and applied in practical examples to evaluate the effectiveness of lumped models, 1D and 2D Finite Element Analysis models and coupling Finite Element Analysis with Circuit Simulation. An original approach, linking SPICE with a Finite Element Analysis solver is presented and evaluated. Practical test cases illustrate the effectiveness of the models used in a variety of contexts. A Passive Fault Current Limiter (FCL) was investigated using a saturable inductor with a magnet offset, and the comparison between measured and simulated results allows accurate prediction of the behaviour of the device. A series of broadband hybrid transformers for ADSL were built, tested, modeled and simulated. Results show clearly how the Total Harmonic Distortion (THD), Inter Modulation Distortion (IMD) and Insertion Loss (IL) can be accurately predicted using simulation.A new implementation of ADSL transformers using a planar magnetic structure is presented, with results presented that compare favourably with current wire wound techniques. The inclusion of transformer models in complete ADSL hybrid simulations demonstrate the effectiveness of the models in the context of a complete electrical system in predicting the overall circuit performance

Mixed-signal integrated circuits design and validation for automotive electronics applications

Automotive electronics is a fast growing market. In a field primarily dominated by mechanical or hydraulic systems, over the past few decades there has been exponential growth in the number of electronic components incorporated into automobiles. Partly thanks to the advance in high voltage smart power processes in nowadays cars is possible to integrate both power/high voltage electronics and analog/digital signal processing circuitry thus allowing to replace a lot of mechanical systems with electro-mechanical or fully electronic ones. High level modeling of complex electronic systems is gaining importance relatively to design space exploration, enabling shorter design and verification cycles, allowing reduced time-to-market. A high level model of a resistor string DAC to evaluate nonlinearities has been developed in MATLAB environment. As a test case for the model, a 10 bit resistive DAC in 0.18um is designed and the results were compared with the traditional transistor level approach. Then we face the analysis and design of a fundamental block: the bandgap voltage reference. Automotive requirements are tough, so the design of the voltage reference includes a pre-regulation part of the battery voltage that allows to enhance overall performances. Moreover an analog integrated driver for an automotive application whose architecture exploits today’s trends of analog-digital integration allowing a greater range of flexibility allowing high configurability and fast prototipization is presented. We covered also the mixed-signal verification approach. In fact, as complexity increases and mixed-signal systems become more and more pervasive, test and verification often tend to be the bottleneck in terms of time effort. A complete flow for mixed-signal verification using VHDL-AMS modeling and Python scripting is presented as an alternative to complex transistor level simulations. Finally conclusions are drawn

Runtime Verification of Analog and Mixed Signal Designs

Analog and mixed signal (AMS) circuits play an important role in system on chip designs. They pose, however, many challenges in the verification of the overall system due to their complex behaviors and expensive consumption of simulation resources. Besides functionality, AMS systems also suffer from stochastic processes such as random noise which exhibits statistical properties. Among many developed verification techniques, runtime verification has been shown to be effective by experimenting finite executions instead of going through the whole state space. In this thesis, we propose a methodology for the verification of AMS designs using functional and statistical runtime verification. Functional runtime verification is used to check the functional behavior of the AMS design. A system of recurrence equation (SRE) is used to model the AMS design and construct a functional property monitor. This functional runtime verification is carried out in an online fashion. Statistical runtime verification is used to verify the statistical properties of the AMS design. Hypothesis test, which is a method to make statistical decisions about rejecting or accepting some statement about the information of a sample, is used to verify the statistical properties. We use Monte Carlo simulation for the hypothesis test and for evaluating its performance. The proposed methodology is applied to a phase lock loop based frequency synthesizer where several functional properties and stochastic noise properties are verified