In this subgroup of the ESAT-MICAS division design methodologies and related algorithms and computer-aided design (CAD) software tools are being developed to be used by analog and mixed analog-digital designers. The goals of these activities are to increase the productivity of analog designers (shorten the time to market) and to improve the quality and optimality of analog and mixed-signal IC designs (e.g. power reduction, but also avoiding expensive redesign runs). The activities can be divided in four themes.
1. Mixed-signal system design and exploration methodologies
The first theme deals with methodologies and tools for the design of mixed-signal integrated systems ("systems on a chip"), such as for telecom applications. This includes techniques for system-level architectural exploration and trade-off analysis. For example, a tool called ORCA was developed for the frequency-domain behavioral analysis of wireless receiver front-ends at the architectural level. For typical input power spectra the tool computes the power distribution of the wanted signal components, as well as those of all non-ideal signals (such as noise, distortion, aliasing, phase noise) generated in the receiver front-end. An example is shown in the figure. In this way, high-level explorations of different front-end architectures become possible, as well as a quantitative analysis of trade-offs such as determining the optimal partitioning between analog and digital. Other system-level topics under study are techniques to facilitate technology porting and to enable analog design reuse for Virtual Socket Interface (VSI) compliant block-based system design.
2. Analog circuit modeling and simulation
A second theme relates to the development of techniques for analog circuit modeling and simulation. For system-level simulations, research is conducted on the automated generation of analog behavioral models, as well as on the development of accurate yet efficient power and area estimators that return a good estimate of the power and area consumption needed to implement a certain block with given specification values. At the circuit level, both symbolic and numerical simulation techniques are being developed to fill holes in the commercial EDA offerings. For example, the ISAAC program and its newest version SYMBA is a symbolic simulator that generates simplified analytic equations for the small-signal characteristics of linearized and weakly nonlinear analog integrated circuits. These expressions help the designer in better understanding the functioning of his circuit. They can also be used in other applications, like in circuit sizing and synthesis. An example of a pure numerical technique that has been developed is the efficient simulation of phase noise in oscillators and phase-locked loops.
3. Analog circuit and layout synthesis
A third theme concerns the development of techniques for analog circuit and layout synthesis. Here both interactive and automated approaches are being explored, with as final goal to speed up the overall design process, without sacrificing performance. Example tools here are the constraint-based circuit sizing tool DONALD that generates a design plan from a declarative analytic description of the circuit. Designers can then numerically evaluate the analytic model of the circuit in arbitrary directions, for example from performance specifications to sizes or vice versa. The tool allows both interactive and optimization-based analog circuit sizing. The AMGIE system is a prototype synthesis tool that offers designers an almost completely automatic path for the customized design of analog blocks. The tool covers the complete design flow from specifications over topology selection and circuit optimization down to layout generation and detailed characterization and datasheet extraction, and is integrated in a commercial EDA framework. Target circuits are operational amplifiers and filter structures. An example of an automatically synthesized particle detector front-end is shown in the figure. For high-performance circuits like data converters the system is used more interactively as a tool box. Finally, the LAYLA tool implements a performance-driven layout synthesis approach that performs a custom placement and routing of analog circuits such that the layout-induced performance degradation remains within the allowed margins. For more regular array-type of structures like certain data converters the Mondriaan tool was developed.
4. Analog and mixed-signal testing
The last theme is the testing of analog and mixed-signal integrated circuits. Techniques for automatic defect-based analog test pattern generation have been developed. Especially the use of power-supply current spectrum monitoring has been explored. Recent focus is on the testing and self-test of embedded analog blocks.