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AVOIDING ANALOG DESIGN SEGREGATION Will electronics design chain optimization ever include analog design? By Geoffrey James Optimizing Design chains is always a challenge. Anyone who's tried to coordinate the activities of multiple groups inside multiple companies knows it's not an activity for the faint of heart or those of little faith. That already formidable challenge, however, is vastly magnified when analog circuitry is added into the mix. For one thing, the relative scarcity of analog design engineers forces many firms to do extra subcontracting to obtain access to analog expertise, and this adds complexity to the design chain. To make matters worse, analog designs can spawn alarming delays in design and manufacturing schedules, adding extra expense and threatening time to market. One thing is certain, an increasing number of semiconductor firms will be involved in design chains that include analog circuitry. The percentage of die space dedicated to analog circuitry worldwide has nearly doubled since 1997 and is expected to grow as high as 15 percent by 2008, according to Rich Wawrzyniak, a senior analyst at Semico, a market research firm. That creeping growth of analog may mean major hassles for semiconductor firms that want to get a working product out the door on time and within budget (see the table "Estimated Worldwide Percentage of Die Area Dedicated to Analog"). Not to worry. Electronics Design Chain polled experts on how to manage the business and collaboration challenges that stem from designing chips with analog content. Here are five key guidelines for making sure analog doesn't become the weak link in your design chain. GUIDELINE #1. Create collaborative partnerships. Many digital-only design chains assume traditional vendor/customer relationships, with a well-defined hand-off of information from the system customer to the design organization, then to mask manufacturer, and then to wafer manufacturing. The players expect the business relationships to be somewhat formal, and each player in the design chain tends to operate independently, trusting that the other players will do their jobs correctly. That doesn't work very well when there's analog content in the chip, though. Analog adds design complexity and thus requires greater levels of cooperation between the companies participating in the chain. The specific relationship between design and manufacturing is a case in point. "From a business perspective, the biggest worry from the design side is unexpected manufacturing variations, which can lead to problems with performance, extra manufacturing yield cost, and additional design iterations required to fix these problems," explains Dhrumil Gandhi, a senior vice president at Artisan Components, an analog/mixed-signal IP supplier in Sunnyvale, Calif. "Analog designs require collaborative partnerships, which means sharing of sensitive information and understanding of each other's limitations," adds Gandhi. That attitude of collaboration must reach all the way back to the system customer, according to Art George, vice president of the high-performance analog division at Texas Instruments in Dallas, Tex. "It's important that the IC supplier considers the customer, which has the system expertise, as an integral part of the development team," he says. "It's not enough for the customer to be just a participant or a consultant." GUIDELINE #2. Cross-pollinate your design chain teams. For the design chain to run smoothly, the collaborative partnership between the firms in the chain must be manifested in the composition of the individual teams. Each design and manufacturing team should have at least one engineer who is familiar with the work of the other teams that his or her team deals with. For example, it is absolutely critical that every analog design team include at least one engineer who understands digital design. Similarly, an analog-trained engineer should be on every digital design team. "This reduces overall problems and makes it easier for the teams to work together," says Robert B. Pease, staff scientist at National Semiconductor Corp. in Santa Clara, Calif. Cross-pollination is also essential between manufacturing teams and design teams. "The manufacturer needs clear guidance from the chip designer about the most sensitive parameters for the design," explains Gandhi. "This is specially true for analog designs, which tend to be the most sensitive part of the chip." "Without fail, we underestimate how much time it will taketo complete the analog portion of a design chain." Richard Gray, Analog Microelectronics Unfortunately, it's often difficult to find engineers who have multiple skill sets. In fact, "there are only about 4,000 trained analog designers in the United States," according to Gary Smith, an EDA analyst at Gartner Dataquest. As a result, "engineers who are 'bilingual' or 'trilingual' are worth their weight in gold," says Dave Robertson, a product line director for high-speed converters at Analog Devices in Norwood, Mass. To provide this expertise, it's often necessary to bring in outside organizations that have familiarity with analog design. GUIDELINE #3. Plan ahead for possible schedule delays. Digital design and analog design are fundamentally different. Digital designers are armed with sophisticated tools that automate everything from synthesis to layout, making the design process relatively predictable. Analog designers, by contrast, lack such sophisticated tools and thus must take a bottom-up approach, repeatedly laying out and testing the circuitry until it works properly. Because of this, analog design schedules are simply less predictable than those of purely digital designs, according to Erach Desai, an EDA analyst at American Technology Research. Indeed, even companies that make their revenue from analog design sometimes throw up their hands in surrender when it comes to accurately predicting when an analog design will be complete. "Without fail, we underestimate how much time it will take to complete the analog portion of a design chain," says Richard Gray, vice president at Analog Microelectronics, a supplier of analog semiconductors in Mainz, Germany. The danger, from a design chain perspective, is that delays in the analog design will ripple through the entire chain, resulting in schedule delays that can cause a chip to miss its window of opportunity. The best way to prevent this is to build some extra time into the schedule to accommodate possible delays in the design and manufacturing of the analog circuitry. "You've got to be prepared to keep redesigning, even though the overall schematic hasn't changed," explains Pease.  Back to School U.S. universities must train more analog designers Amajor challenge to creating effective mixed-signal design chains is the shortage of trained analog designers. Why are there so few? And what can the semiconductor industry do to ensure a steady supply of analog talent in the future? There are three reasons for the dearth of the analog engineers. First, analog design is so difficult that it scares away potential practitioners. "The math and physics requirements for digital engineers are less demanding, and CAD tools exist to do much of the heavy lifting," says Thomas H. Lee, professor of electrical engineering at Stanford University. "For many students, the pain of field theory and Laplace transforms keeps them away from analog design." The second reason for the analog shortage is that engineering departments are broadening their offerings into computer science and biotechnology, sometimes at the expense of traditional engineering disciplines such as analog design. "The problem is not so much a dichotomy between digital and analog design as it is the enormous burden that society is putting on colleges," says Paul Gray, executive vice chancellor and provost at the University of California, Berkeley. Finally, the advent of computer engineering, computer science and biotechnology as major engineering disciplines has tended to direct academic funding away from core engineering coursework. "The absolute size of the engineering higher education establishment in the U.S. is growing much less rapidly than the job market," says Gray. As a result of these reasons, analog design has gotten the short end of the academic stick, resulting in a shortage that makes it difficult for semiconductor firms to get their analog design work completed in a timely manner. Perhaps that won't always be the case, though. Engineering schools are beginning to take more notice of analog design, according to Gray. "You will likely see some gradual increase in funding over the next few years," he promises. However, he also warns that analog engineering is unlikely to experience a dramatic upsurge of academic investment. "There are simply many other critically important areas of engineering that need to be addressed." The best way to ensure that analog design gets its fair share is to make engineering students aware of the salary potential in analog, according to Lee. "Engineering students are good at optimization, and that extends to choosing a professional focus," he says. "Analog engineers are certainly in short supply, and companies have adjusted compensation somewhat to respond to that reality." Beyond this, the semiconductor industry may need to work more closely with academia to ensure that the proper resources are allocated. And there are signs that that's already beginning to happen. National Semiconductor, for example, is working with a college in Silicon Valley to mentor students in the field of analog design.—G.J. GUIDELINE #4. Minimize design chain dependencies. Given that delays in the analog design process are next to inevitable, it's madness to tightly couple the digital segments of a design chain with the analog segments. Instead, reduce dependencies to a minimum, so that analog delays have a minimal impact on the rest of the chain. The best way to do this is to set up parallel design paths with separate milestones. You should also break the analog path into subprojects, so that the analog content can be gradually integrated into the digital content, rather than risking everything on a single end-of-design integration crunch, according to Steve Parks, director of marketing for high-performance analog at Texas Instruments. "If the analog elements of a chip are, for example, broken into the portion that handles the signal and the portion that handles the power, the signal portion can be developed first. That way, it can be more quickly integrated with the digital elements that constitute the brains of the chip. The power management module can be integrated later, when the power consumption of the digital portion of the chip is better understood." GUIDELINE #5. Communicate, communicate, communicate. Even if the previous four guidelines are followed religiously, it is the quality of the ongoing communication between teams that will ultimately determine whether a project is successful, according to A. J. Sen, CEO of Astro Semiconductor, an analog IP supplier in San Jose, Calif. "Having lots of communication is the only way you can be certain that the analog/digital integration works," he insists. There are four primary ways to ensure a desirable free flow of communication: 1. Create a comprehensive and clear specification. It seems obvious, but doing the up-front paperwork is one of the best ways to keep a design chain running smoothly. Organizational confusion and schedule delays can be held to a minimum when everybody on the project team has a "bible" that describes what the chip is supposed to do and how it's supposed operate. "First and foremost, a well-defined specification is paramount, to avoid ambiguity," says TI's George. 2. Schedule multiple face-to-face meetings. Now that e-mail and instant messaging are commonplace, there's a temptation to save time and money by reducing business travel. But that's a big mistake, according to Robertson. He insists that it's essential for members of the various teams to get to know one another face to face and build personal working relationships. "If that means a fair bit of travel, then so be it," he says. 3. Appoint a strong project manager. The more engineers working on a project, the more important it is to have a single point of contact working cross-organizational issues. Ideally, a project manager should have broad experience in all phases of the design chain and the diplomatic skills to work with engineers in a variety of environments. "I've never seen a successful design completed with a customer without superb project management," says George. 4. Drive for consensus between design philosophies. Analog engineers tend to be older, more conservative, and more skeptical about automation than their digital counterparts. This creates a danger that differences in design philosophy may make it difficult to keep the chain running smoothly. "Design meetings can end up like United Nations debates," Robertson warns. To avoid this, management must constantly strive to raise technical discussions above the "how should we design" level to the "how can we achieve" level, according to Robertson. "You've got to depoliticize the design effort, so that the various groups see eye to eye," he says. Decoupling Design Finally, if time to market really is the paramount concern, it may make sense to completely decouple analog and digital by breaking the project into two separate chips. Although this sounds like heresy to those committed to the system on a chip (SoC) concept, there are some advantages to this approach, according to Gray. "Why not take an analog chip that already works rather than create a brand-new complicated, multilayered SoC?" he asks. Gray points out that "putting the analog on a separate chip makes the design chain more flexible, because it's easier to change things on the fly without affecting the rest of the design." National Semiconductor's Pease puts it somewhat more bluntly: "The mindless rush to put everything on one chip has been overdone." ABOUT THE AUTHOR Geoffrey James writes frequently about EDA for Electronic Business. His work has appeared in Computerworld, CIO, Red Herring, Upside, Business 2.0 and Men's Health. Contact him at gjames@designchain.com.

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