Technical Papers

Interoperable PDK: Accelerating Analog EDA Innovation

Jingwen Yuan
Strategic Alliance Manager
Synopsys, Inc.
July 9, 2009

While digital design automation has moved forward with amazing speed over the last 20 years, analog automation has lagged far behind. With RF and consumer devices demanding increased integration, the analog portion is now the gating factor on many, if not all SoC designs. This disparity exists because analog is a fundamentally harder problem to automate than digital. During the planning stage of a SoC design managers use the following rule of thumb for scheduling. "2% of transistors = 40% of design effort" The analog 2% require painstaking manual effort that takes up almost half of the design team effort. Customers have the economic motivation to automate analog design, but they just can't get the tools.

The lack of tools is not just a technology problem resulting from stifled innovation. Even if engineers could get the tools they would still lack the infrastructure that is needed to support a viable ecosystem. Such an ecosystem would need several companies working together to fill every niche and competing to provide the best solution. But before you can have a vibrant ecosystem you need a set of standards that enable interoperability. The custom design ecosystem needs a standard for Process Design Kits (PDKs).

A PDK is a comprehensive set of foundry-verified data files including parameterized layout cells (PCells) used in an analog and mixed signal design flow. Today's PDKs are proprietary and incompatible. PDKs written in proprietary languages and operated on proprietary databases have limited design reuse and prevent designers from adopting best-in-class tools. Proprietary formats eventually slow down EDA innovation.

The IPL (Interoperable PDK Libraries) Alliance, an industry-wide collaborative effort to create and promote standards of interoperable PDK, announced last year at DAC that Taiwan Semiconductor Manufacture Co. Ltd. (TSMC) agreed to join the alliance. This news accelerated the momentum of the standardization effort. TSMC is now working with key IPL Alliance members on an interoperable PDK for TSMC 65nm process technology.

Without interoperable PDKs, each foundry has to create multiple tool-specific PDKs for different EDA tools. The numbers are staggering. TSMC alone developed, distributed and maintained 2,500 PDKs and technology files in 2007 alone. The standardization of PDKs benefits analog and custom IC designers by removing bottlenecks in multiple-vendor flows. Standardization can reduce PDK development cost and schedule, providing designers quicker access to new advanced process technologies.

An interoperable PDK benefits the entire chain of semiconductor companies, foundries and EDA vendors. Semiconductor companies will be able to use one unified interoperable PDK to provide advanced functionality across multiple EDA vendor tools, improve design accuracy, shorten design cycle times, and promote design reuse. These benefits improve the return on design investment. Foundries reduce their PDK development, validation, support and distribution costs while expanding the number of tools they support. EDA vendors will also be able to reduce PDK development costs, while supporting a wider range of foundry partners.

Interoperable PDK is based on the OpenAccess database and uses standard languages such as Tcl and Python that ensure interoperability among all EDA vendor tools. These interoperable PDKs include a comprehensive set of APIs to enable customization, support advanced PDK features and provide an interactive environment for PDK development. PCells written in Python (PyCells) not only have significantly fewer lines of codes, but also provide tremendous performance improvement compared to relative object based SKILL PCells. PyCells support advance features such as abutment, stretch handles and DFM rules. PyCell Studio from Ciranova and IDE provide interactive environment for PyCell development and efficient PyCell debugging therefore improve PCell development productivity and shorten PDK development cycle. High-level Python APIs provides process porting capability within PDKs. No need to code PyCells for different process, just swap out tech files. This has great benefits for IP groups. When it comes to PDK validation, because interoperable PDK is based on OA, no stream-in or stream-out or any shape of data translation is needed among all leading physical verification tools. This makes PDK validation effortless.

Analog design has been characterized as "black magic" for its difficulty and complexity. Much of the design is still done with less automation compare to digital design. Interoperable PDK as the building block for any analog design will enable design reuse, improve design productivity and ultimately promotes innovation in analog and full custom EDA.