MESH: Explicit and flexible generation of analog arrays

Abstract

Analog layout design is a costly and error-prone task since analog synthesis is still far from applicable. It is expected that procedural bottom-up generators managing constructive tasks will be part of future synthesis flows. Generators contain expert knowledge implicitly within complex and hard-to-understand source code. Due to a lack of explicit layout definition and uncaptured design intent, generator layouts can hardly be adapted by constructive algorithms directly. Thus, synthesis flows need to adapt layout blocks by varying generator parameters which results in computation-expensive optimization. This paper introduces MESH—a software structure to define detailed and flexible layout generators explicitly. Using MESH, just a few lines of code describe complex layouts while all relations and design intents, such as element positions and routing styles, are captured through abstract commands. As a result, generators are created fast with less programming errors, and constructive algorithms can modify the generator structure directly

Generating the Generator: A User-Driven and Template-Based Approach towards Analog Layout Automation

“…The respective advantages and disadvantages are discussed in the following subchapters. Automatic generator code creation with a schematic as the input that allows immediate generation of non-hierarchical matrix-style layouts [10].…”

“…With the Berkeley Analog Generator (BAG) [4], a first open-source attempt covering a variety of target PDKs was presented. A second version of the BAG followed [35], and new layout engines such as MESH [8] for regular array-style layouts or LAYGO [36] to especially support gridded FinFET layout styles were proposed.…”

“…Key extensions towards (matrix-style) templates have been presented in refs. [8,10], of which the latter also creates generator code automatically for non-hierarchical matrix-style blocks. These extensions have been further developed in the presented work and now support both hierarchical blocks and further template styles.…”

“…Automatic generator code creation with a schematic as the input that allows immediate generation of non-hierarchical matrix-style layouts [10].…”

From Constraints to Tape-Out: Towards a Continuous AMS Design Flow

“…Recently, new template-driven generator approaches were presented [12], [13] which implement the template approach [14]- [16] into procedural generators. The basic idea is to overcome error-prone procedural descriptions which do not allow direct algorithmic access to the generator code.…”