Innovative Ideas for Predictable Success
      Volume 3, Issue 4

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Technology Update Technology Update
Addressing Modern-Era AMS Design Needs
While the needs of custom designers have moved on, the tools that they use for custom design have not... Ed Lechner, director of product marketing for custom design, and Graham Etchells, director of marketing for AMS, both Synopsys, outline Galaxy Custom Designer, a user-friendly tool that gives designers a highly productive, unified solution for both custom and cell-based designs.

Many new challenges have emerged during the past 10 years in custom and analog/mixed-signal (AMS) design. Design teams faced with new technologies and business drivers can find themselves at a competitive disadvantage: often they are struggling to manage their designs efficiently using proprietary custom design tools that were originally architected for discrete analog and digital ICs. Solutions that were good enough 10 years ago no longer offer designers a productive design platform because they are fragmented and incomplete.

Custom Design Trends
AMS circuitry is now critical to the success of modern consumer SoC designs, and virtually all designs now contain some custom design elements. While it might only make up 10 percent of a total design, according to an IBS report, AMS design content typically represents about 50 percent of the chip cost, while problems with AMS circuitry account for 70 percent of design respins. These stark facts illustrate the importance of getting custom design right.

The modern AMS era is characterized by designs that more tightly couple analog and digital design – the boundaries between them are becoming more blurred, and there is much greater interdependency between the two domains. For example, functions that have traditionally been designed using analog techniques, such as PLLs and converters, now contain more digital functionality. Similarly, it is more common for designers to embed memory within their SoCs, which often demands a custom design approach.

Designs that unify analog and digital functionality need tools that can manage that integration. Tools for the modern AMS era must enable more productive design. They must support efficient exchange of data between analog and digital analysis tools, and enable effective analog IP reuse.

Unified Solution
Synopsys' Galaxy™ Custom Designer™ is a new, comprehensive solution that unifies custom and cell-based design. It provides both custom implementation and verification capabilities within a single environment, including simulators, waveform analysis and extraction technology. By integrating Custom Designer with Synopsys' IC Compiler, designers are able to manage digital and analog physical implementation, including route editing, in a single, unified environment (Figure 1).


Figure 1. Galaxy Implementation Platform including Custom Designer

Improving Productivity
Custom Designer is a completely new product, and was designed and built with productivity in mind. It is easier to use than competing tools, which boosts designers' efficiency.

For example, Custom Designer's ‘on canvas' editing reduces the number of mouse clicks needed for repetitive operations such as changing device property values and net name editing, thereby speeding up an everyday task that can be a time-consuming part of the creation process for custom designers. Custom Designer also provides 'dynamic connectivity' – laying down a connection will automatically assign it a net name and reduce time-consuming errors that can be caused by wrong connections. It also has an efficient menu structure that streamlines data entry and allows designers to perform common tasks quickly and easily.

These usability features are all available out-of-the-box – there is no need to customize the environment. Collectively, they can save designers many hours of time and allow them to be productive from the outset. New users of Custom Designer who are switching from other tools appreciate the familiar look and feel that makes using the tool very intuitive.


Figure 2. Easy-to-use schematic editor saves designers hours of time

Another feature that eases adoption is the OpenAccess database, which makes it easy for designers to import legacy data. OpenAccess is the industry's first open system that supports interoperable libraries (or foundry-interoperable process design kits – iPDKs) – TSMC is collaborating with Synopsys to develop these.

High levels of automation also support improved productivity across the whole custom design solution. For example, integration with Synopsys' Hercules™ solution supports push-button design rule checking (DRC). Similarly, integration with Synopsys' HSPICE® and WaveView Analyzer allows fast simulation setup, execution and analysis, in addition to cross-probing from both the schematic and layout windows.

Custom design data is characterized by extremely large (gigabyte) files. In other systems, designers will often have to translate the design database into other intermediate formats before they can manipulate it using other tools in the flow. And then they have to transfer the data back again. These translation operations are a real obstacle to productive design, as they can take many hours and consume significant CPU resources.

Custom Designer's tight integration with other tools in the Galaxy Implementation Platform improves overall productivity. By streamlining the exchange of design data through an optimized link with IC Compiler, exchanging vital information during floorplanning, placement, routing and final chip editing significantly improves turnaround time for custom design.

Analog IP
Designers want to share analog blocks both within and outside their organizations. The development of easily reusable analog IP will let them do this. P-cells, the parameterized cells that form the basic analog elements such as transistors, diodes, capacitors and resistors, are the fundamental building blocks for analog physical design.

Today, the extensive use of proprietary languages to develop P-cells makes it very difficult to port analog IP between different process technologies. Because Custom Designer is built on OpenAccess, and also supports the use of open languages like Python, TCL and C++ to develop P-cells, it enables IP to be developed that can be easily ported between vendors without custom programming. P-cells for 65-nm technologies may comprise hundreds of lines of code and need to accommodate hundreds of parameters, so custom programming requires significant expertise and can be very time-consuming.

The standardization of PDKs will further encourage an interoperable approach to defining the basic building blocks of analog design. Custom Designer supports the IPL Alliance's Interoperable PDK libraries for industry-wide sharing of design data. This initiative aims to deliver one PDK for all tools, which will eliminate the porting time for PDK libraries – typically around 12 weeks per library.

Summary
The challenges of modern-era AMS design present an opportunity for Synopsys to help design teams transform their design productivity for custom implementation, just as it did for digital implementation with the introduction of Design Compiler®.

Custom Designer extends the Galaxy Implementation Platform to provide a single, unified solution for both custom and cell-based designs. Its open architecture enables design portability and supports analog reuse. Its integration with Star-RCXT™ and Hercules provides a complete solution for physical verification. It also works with Synopsys' best-in-class circuit simulators including HSPICE, HSIM™ XA, and NanoSim® XA, as well as WaveView Analyzer for efficient analysis and debugging.

Ed Lechner
Ed Lechner is director of product marketing for custom design at Synopsys.

Graham Etchells
Graham Etchells is director of marketing for AMS at Synopsys.



©2008 Synopsys. Synopsys, Inc., the Synopsys logo, Design Compiler, Galaxy, Hercules, HSIM, HSPICE, NanoSim and Star-RCXT are registered trademarks or trademarks of Synopsys, Inc. All other company and product names mentioned herein may be trademarks or registered trademarks of their respective owners and should be treated as such.


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"AMS design content typically represents about 50 percent of the chip cost, while problems with AMS circuitry account for 70 percent of design respins."