A reuse-based framework for the design of analog and mixed-signal ICs

Rafael Castro-Lopez, Francisco V. Fernandez, Angel Rodriguez Vazquez, Jose F. Lopez, Francisco V. Fernandez, Jose Maria Lopez-Villegas, Jose M. de la Rosa
<span title="2005-06-30">2005</span> <i title="SPIE"> VLSI Circuits and Systems II </i> &nbsp;
Despite the spectacular breakthroughs of the semiconductor industry, the ability to design integrated circuits (ICs) under stringent time-to-market (TTM) requirements is lagging behind integration capacity, so far keeping pace with still valid Moore's Law. The resulting gap is threatening with slowing down such a phenomenal growth. The design community believes that it is only by means of powerful CAD tools and design methodologies -and, possibly, a design paradigm shiftthat this design gap can
more &raquo; ... be bridged. In this sense, reuse-based design is seen as a promising solution, and concepts such as IP Block, Virtual Component, and Design Reuse have become commonplace thanks to the significant advances in the digital arena. Unfortunately, the very nature of analog and mixed-signal (AMS) design has hindered a similar level of consensus and development. This paper presents a framework for the reuse-based design of AMS circuits. The framework is founded on three key elements: (1) a CAD-supported hierarchical design flow that facilitates the incorporation of AMS reusable blocks, reduces the overall design time, and expedites the management of increasing AMS design complexity; (2) a complete, clear definition of the AMS reusable block, structured into three separate facets or views: the behavioral, structural, and layout facets, the two first for top-down electrical synthesis and bottom-up verification, the latter used during bottom-up physical synthesis; (3) the design for reusability set of tools, methods, and guidelines that, relying on intensive parameterization as well as on design knowledge capture and encapsulation, allows to produce fully reusable AMS blocks. A case study and a functional silicon prototype demonstrate the validity of the paper's proposals. Keywords: Analog and Mixed-Signal IP Block, Design Reuse, Design for Reusability, CAD. Downloaded From: https://www.spiedigitallibrary.org/conference-proceedings-of-spie on 27 Jan 2020 Terms of Use: https://www.spiedigitallibrary.org/terms-of-use Although the level of computer digital design automation is far from the push-button stage in the digital arena, the development of digital CAD tools and methodologies are moderately keeping pace with chip density 1 . Unfortunately for AMS CAD resources, the picture so far is much less optimistic, lagging several generations behind the digital ones. A main reason for this detainment is the specialized knowledge and almost handicraft design skills, usually acquired after many years of experience, that analog and mixed-signal design entails, the wide heterogeneity of AMS circuits blocks and designs, the looseness of the hierarchy definition, as well as their extreme sensitivity to several sources of noise such as layout-induced parasitics. Due to all these features, AMS design is still regarded as less systematic, far more knowledgeintensive, and heuristic than digital design. A large amount of analog and mixed-signal circuits are still designed without any really robust and commercial CAD tools but a SPICE-like simulation shell and an interactive and scarcely automated layout environment [3] . Consequently, as fabrication technology progresses and new technology nodes come out, AMS designers are unable to deal with increasing TTM pressures and design complexity, turning AMS design into a clear and present bottleneck of the overall design process. Considering estimates indicating that 30% of today's ICs include some analog or mixed-signal content (this percentage is expected to grow to over 60% in the next few of years), and the fact that the time required to design AMS content usually dominates the total design time, it is clear that, for the semiconductor industry to maintain its design productivity, an efficient CAD methodology and adequate CAD tools to design AMS circuits are urgently required. In this sense, a number of goals to improve modern top-down, bottom-up, hierarchical design methodologies have been defined in the 2001 ITRS report [4]. Among them, this paper addresses the following three goals, whose pivotal issue is the shifting of today's AMS methodologies to the reuse-based design paradigm that, together with adequate synthesis tools, is seen as one of the most promising solutions to face stringent time-to-market pressures and increasing complexity of AMS design: 1. Reuse. To extend the notion of library-based approaches, and thereby reduce overall design time, reuse and capturing AMS designers' expertise should be a major concern. 2. Improve automated synthesis. AMS circuit design typically requires very specific expert knowledge that should be incorporated into the various automated synthesis processes in order to enhance their efficiency. Hierarchical synthesis with performance specification management and transmission, is mandatory. 3. Avoid iterations. Spins between electrical and physical synthesis, accounting for many layout-induced sources of degradation, that eventually lead into product-to-market failure, should be reduced or completely removed. The contents of the paper are organized as follows. Section 2 provides and overview of the reuse-based design concepts in the AMS arena and a syncretic review of previous approaches. Section 3 presents an integral reuse-based design framework for AMS circuits. A case study is analyzed in Section 4. Conclusions are drawn in Section 5.
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