Deciphering the analog automation code

It would not be too much of a stretch to say that automated electronic design software has already revolutionized the design of semiconductors—for digital circuits.

In the mid-1990s, a number of companies introduced automatic place and route tools that fundamentally changed the world of digital layout. And the productivity gains continue to enable todays massive chip designs.

Why automate?
Analog layout, on the other hand, is still generated at the device level. By necessity, it must be fairly free form in order to meet a number of analog-specific layout constraints. The process is iterative, creative—even, some say, an art form. Over time, analog layout designers have steadfastly eschewed attempts to automate the process, and numerous products and companies have died trying. After all, even schematic-driven layout, which has been around for some time, is not yet universally deployed.

If there is so much resistance from users, why automate at all? Although a black-box automated analog layout solution is somewhere between impractical and impossible today, that doesnt mean that nothing can or should be done. In all likelihood, all but the most intransigent designers would be willing to employ effective automation if they felt comfortable with the use model and results.

Analog is an area that is begging for automation because of the ever-increasing analog content of consumer products, the sheer size of todays designs and the increasingly complex manufacturing constraints of advanced processes. The key is to enable analog design, not try to imitate an innately creative process.

The goal, therefore, is to empower layout designers to simply and automatically generate and place design rule checking (DRC)-clean, analog-aware layout of sufficient quality to give them confidence in the functionality. Then, we must include tools that allow them to iterate quickly to an optimal solution equal or superior to handcrafted layout. Inaccurate or incomplete solutions will drive layout designers back to their comfort zone, to rely on their own hand-layout skills.

Make it intuitive
The challenge for vendors is to make the designers interaction with the tool seem like second nature. Automated custom layout tools should be an extension of the designer, providing intuitive aids to do what they already do in a simple, highly accurate and, not coincidentally, more productive way.

A device-level floor planner with a symbolic stick diagram tied to a built-in placer magnifies the designers own skills. So does a point-to-point router that follows the mouse, jumps up levels of metal at a push of a button, recognizes blockages and instantly identifies shorts and DRC violations. Use the guided router to route a 128-line bus, and productivity soars; but it must still look and feel as natural as a single-wire route.

Does the inflection point at which designers will embrace analog automation start at one wire or at 128? Does it lie with automated design-for-manufacturability rules, current-limited wire width, interoperable p-cells, constraint-driven flows with custom placers and custom routers, or the accumulated benefit of all these things?

In the end, automation from rule-driven to constraint-driven flows should allow the designer to choose how much to use and how to use it. Analog automation—controllable automation—not only guides the execution of the designers skills, but also reduces the amount of required information (such as recommended design rules) to a level that a layout designer finds useful and non-intrusive. Automating the myriad details of analog layout allows layout designers to focus on the creative aspects of design, where they naturally excel.

Automation will never fully replace human perception and intuition, but we can deploy tools that will generate automated custom layout in a way that avoids errors in an increasingly complex design environment, providing high-quality first-pass layout. Over time, such tools will reduce the number of iterations required and the amount of optimization necessary to approach handcrafted quality.

Empower human perception
But designers are unlikely to relinquish control to get there. Thus, tool vendors must enable layout designers to intercede easily to analyze and modify the choices made or the parameters used by the automation itself. At the same time, they must empower human perception to optimize the results by giving designers the tools to execute modifications quickly and confidently.

The better we get at providing tools that improve the lot of analog layout designers, the more likely they are to embrace automated custom layout.

- Richard Morse
Director of Marketing
Silicon Canvas Inc.

This article was printed from EE Times-Asia located at: http://www.eetasia.com/ART_8800523108_499495_NT_f3128dfd.HTM