David J. Garrod

Bio: David J. Garrod is an academic researcher from Carnegie Mellon University. The author has contributed to research in topics: Routing (electronic design automation) & Anagram. The author has an hindex of 6, co-authored 6 publications receiving 694 citations.

KOAN/ANAGRAM II: new tools for device-level analog placement and routing

Abstract: The authors describe KOAN and ANAGRAM II, new tools for device-level analog placement and routing. Analog layout tools that merely apply known digital macrocell techniques fall short of achieving the density and performance of handcrafted analog cells. KOAN and ANAGRAM II differ from previous approaches by using general algorithmic techniques to find critical device-level layout optimizations rather than relying on a large library of fixed-topology module generators. New placement algorithms implemented in KOAN handle complex layout symmetries, dynamic merging and abutment of individual devices, and flexible generation of wells and bulk constants. New routing algorithms implemented in ANAGRAM II handle arbitrary gridless design rules in addition to over-the-device, crosstalk-avoiding, mirror-symmetric, and self-symmetric wiring. Examples of CMOS and BiCMOS analog cell layouts produced by these tools are presented. >

KOAN/ANAGRAM 11: New Tools for Device-Level Analog Placement and Routing

Abstract: The authors describe KOAN and ANAGRAM II, new tools for device-level analog placement and routing. Analog layout tools that merely apply known digital macrocell techniques fall short of achieving the density and performance of handcrafted analog cells. KOAN and ANAGRAM II differ from previous approaches by using general algorithmic techniques to find critical device-level layout optimizations rather than relying on a large library of fixed-topology module generators. New placement algorithms implemented in KOAN handle complex layout symmetries, dynamic merging and abutment of individual devices, and flexible generation of wells and bulk constants. New routing algorithms implemented in ANAGRAM II handle arbitrary gridless design rules in addition to over-the-device, crosstalk-avoiding, mirror-symmetric, and self-symmetric wiring. Examples of CMOS and BiCMOS analog cell layouts produced by these tools are presented. >

Automatic layout of custom analog cells in ANAGRAM

Abstract: ANAGRAM models cell layout in the style of a macrocell place-and-route problem. Individual cell primitives (transistor-level objects of widely varying sizes) are the macrocells. Module generation techniques are used to generate these internal primitives and to preserve critical matching and symmetries. An annealing-based placement algorithm then places these primitives. This is followed by a novel line-expansion signal router, which includes mechanisms to avoid noise coupling due to internodal capacitances between the signal wires and shared parasitic resistances in the DC supply wiring and operates in an iterative improvement fashion to eliminate such violations. Layouts for several custom CMOS cells have been successfully generated. Circuit-simulation results based on cell extractions demonstrate the effectiveness of the crosstalk-avoidance mechanisms. >

ACACIA: the CMU analog design system

Abstract: A framework that automates the design of common analog integrated circuit modules has been developed. The framework, ACACIA, consists of three tools: OASYS, which transforms module specifications into sized schematics; ANAGRAM, which transforms sized schematics into mask geometry; and a graphics interface that facilitates automatic exploration of tradeoffs between design specifications by providing 3-D display of attainable performance surfaces

Techniques for simultaneous placement and routing of custom analog cells in KOAN/ANAGRAM II

Abstract: The authors describe novel techniques for simultaneous device placement and detailed routing of analog cells. Both nets and devices are treated as placeable, malleable objects in a common simulated-annealing framework. A detailed routing abstraction called a k-bend net limits the complexity of each net's topology, and allows simple incremental net reshaping during annealing. Analog layouts in which the critical interacting nets are simultaneously embedded during device placement prove to be superior, in terms of performance-limiting crosstalk violations, to sequentially placed and routed layouts. >

PathFinder: A Negotiation-Based Performance-Driven Router for FPGAs

Abstract: Routing FPGAs is a challenging problem because of the relative scarcity of routing resources, both wires and connection points. This can lead either to slow implementations caused by long wiring paths that avoid congestion or a failure to route all signals. This paper presents PathFinder, a router that balances the goals of performance and routability. PathFinder uses an iterative algorithm that converges to a solution in which all signals are routed while achieving close to the optimal performance allowed by the placement. Routability is achieved by forcing signals to negotiate for a resource and thereby determine which signal needs the resource most. Delay is minimized by allowing the more critical signals a greater say in this negotiation. Because PathFinder requires only a directed graph to describe the architecture of routing resources, it adapts readily to a wide variety of FPGA architectures such as Triptych, Xilinx 3000 and mesh-connected arrays of FPGAs. The results of routing ISCAS benchmarks on the Triptych FPGA architecture show an average increase of only 4.5% in critical path delay over the optimum delay for a placement. Routes of ISCAS benchmarks on the Xilinx 3000 architecture show a greater completion rate than commercial tools, as well as 11% faster implementations.

Computer-aided design of analog and mixed-signal integrated circuits

Abstract: This survey presents an overview of recent advances in the state of the art for computer-aided design (CAD) tools for analog and mixed-signal integrated circuits (ICs). Analog blocks typically constitute only a small fraction of the components on mixed-signal ICs and emerging systems-on-a-chip (SoC) designs. But due to the increasing levels of integration available in silicon technology and the growing requirement for digital systems to communicate with the continuous-valued external world, there is a growing need for CAD tools that increase the design productivity and improve the quality of analog integrated circuits. This paper describes the motivation and evolution of these tools and outlines progress on the various design problems involved: simulation and modeling, symbolic analysis, synthesis and optimization, layout generation, yield analysis and design centering, and test. This paper summarizes the problems for which viable solutions are emerging and those which are still unsolved.

Optimal design of a CMOS op-amp via geometric programming

Abstract: We describe a new method for determining component values and transistor dimensions for CMOS operational amplifiers (op-amps). We observe that a wide variety of design objectives and constraints have a special form, i.e., they are posynomial functions of the design variables. As a result, the amplifier design problem can be expressed as a special form of optimization problem called geometric programming, for which very efficient global optimization methods have been developed. As a consequence we can efficiently determine globally optimal amplifier designs or globally optimal tradeoffs among competing performance measures such as power, open-loop gain, and bandwidth. Our method, therefore, yields completely automated sizing of (globally) optimal CMOS amplifiers, directly from specifications. In this paper, we apply this method to a specific widely used operational amplifier architecture, showing in detail how to formulate the design problem as a geometric program. We compute globally optimal tradeoff curves relating performance measures such as power dissipation, unity-gain bandwidth, and open-loop gain. We show how the method can he used to size robust designs, i.e., designs guaranteed to meet the specifications for a variety of process conditions and parameters.

Reconfigurable Computing: The Theory and Practice of FPGA-Based Computation

Abstract: The main characteristic of Reconfigurable Computing is the presence of hardware that can be reconfigured to implement specific functionality more suitable for specially tailored hardware than on a simple uniprocessor. Reconfigurable computing systems join microprocessors and programmable hardware in order to take advantage of the combined strengths of hardware and software and have been used in applications ranging from embedded systems to high performance computing. Many of the fundamental theories have been identified and used by the Hardware/Software Co-Design research field. Although the same background ideas are shared in both areas, they have different goals and use different approaches.This book is intended as an introduction to the entire range of issues important to reconfigurable computing, using FPGAs as the context, or "computing vehicles" to implement this powerful technology. It will take a reader with a background in the basics of digital design and software programming and provide them with the knowledge needed to be an effective designer or researcher in this rapidly evolving field. · Treatment of FPGAs as computing vehicles rather than glue-logic or ASIC substitutes · Views of FPGA programming beyond Verilog/VHDL · Broad set of case studies demonstrating how to use FPGAs in novel and efficient ways

OASYS: a framework for analog circuit synthesis

Abstract: A hierarchically structured framework for analog circuit synthesis is described. This hierarchical structure has two important features: it decomposes the design task into a sequence of smaller tasks with uniform structure, and it simplifies the reuse of design knowledge. Mechanisms are described that select from among alternate design styles and translate performance specifications from one level in the hierarchy to the next lower, more concrete level. A prototype implementation, OASYS, synthesizes sized transistor schematics for CMOS operational amplifiers from performance specifications and process parameters. Measurements from detailed circuit simulation and from actual fabricated analog ICs based on OASYS-synthesized designs demonstrate that OASYS is capable of synthesizing functional circuits. >