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Electronic Design

Reference Designs Play A Dual Role

Sometimes, designers take the design and modify it, and other times they use it to the letter. It all depends on market demands.

At one time, reference designs were simply helpful guides to the finer details of designing a part into a board. Those days are long gone. The complexity of today’s devices, in addition to the fast pace of many markets, has forced some reference designs to evolve beyond educational tools into manufacturing documentation for fully defined end products (Fig. 1). This dual role leaves semiconductor vendors struggling to add application expertise to their chip design efforts.

“In the old days, a reference design was just that— a reference,” says Tony Valentino, chief operating officer of QuickFilter Technologies (Fig. 2). “You looked at it for learning, then went on to do your own design.” But the educational role of a reference design began taking a back seat to a new role: becoming a blueprint for end-product manufacturing.

“We still have customers that use these designs as true references, taking our basic circuits and modifying them,” says Valentino. “But now we have customers that take them literally and build our designs just as they are.”

Semiconductor vendors across all industries report the same phenomenon. Reference designs have had to become product designs, complete with schematics, board layout files, bills of material, software, and test procedures. Developers seek such complete designs from their semiconductor vendors for many reasons, including the growing complexity of today’s chips.

“Today, we build systems on a chip,” says Deepak Prakash, director of marketing at Toshiba America Electronics Corp. “There is not much left after that to design in. Also, these chips are so complex that no one outside of the company can understand them as well as we do.”

Ken Lowe, vice president of strategic marketing at Sigma Designs, agrees. “Some of our chips are pushing 7 million gates, with over 1000 registers and 900 pins. The hardware and software are so complex that it is almost impossible to design with them from scratch,” Lowe says (Fig. 3).

While chips have become more complex, customer design expertise seems to have shifted away from board-level details. “The culture has changed in a lot of companies,” says Valentino. “Design engineers are more system-level now and don’t design from the ground up anymore. They look for ready-made designs to drop into their systems.”

Design time has also become a factor, especially in the fast-paced consumer electronics market. Engineers cannot afford the time required to learn the details of a new part and incorporate it into a design when new product variations must continually appear to address rapid obsolescence. “Companies in markets such as DVD players need to get products in and out within a year,” says Lowe, “so they have to go from reference designs straight into production. They can’t add engineering and keep to schedule.”

But it’s not just chips for consumer products that need the support of full-product reference designs. Semiconductor companies are also finding that fullproduct designs are important when jumpstarting any market. “To introduce new technology and enable new markets quickly,” says Sujata Neidig, product manager for audio DSPs at Freescale Semiconductor (Fig. 4), “we need full designs.”

Mario Aleo, division manager for bipolar, IGBT, and RF at STMicroelectronics, feels the same way. “Customers use full reference designs as development kits to understand the potential of new technologies. They also serve as prototypes for testing options and for quick development,” he says.

These many factors have turned full-production reference designs into an essential element of product support for semiconductor vendors, sometimes more important than the product itself. “Customers are making their design decisions based on the reference design, not the chip,” says Lowe. “The assumption is that the reference design brings the full power of the chip out.”

“More and more, our product is being judged on how well the reference design performs,” says Valentino. And, this demand for fully optimized and production-ready reference designs places a huge burden on semiconductor vendors.

One important part of that burden is the design effort that’s required. “Sometimes we have more engineers doing the reference designs than we have doing the original chip,” says Prakash. “In our group, we have as many board and software designers as chip designers.”

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Another vital part of the burden is the need for detailed application expertise. “A reference design has to be targeted to a specific application,” says Valentino, “and we have to be particularly versed in what the end performance requirements of our design must be.”

Companies may also work with third parties to augment their reference design efforts. “Sometimes you have to go out and get expertise,” says Valentino, “in order to address a market in a hurry because you have a short market window.”

Semiconductor companies have developed a variety of strategies to cope with these burdens. One is to focus their efforts only on key markets and components. STMicroelectronics, for instance, has more than 16,000 active part numbers, but only offers about 200 ready-to-go reference designs.

“We attack only those market segments where the added value of our product mix is a major advantage,” says Aleo. The company also multiplies its exposure by incorporating as many STMicro products in a single reference design as possible—from six to 15 on each board, according to Aleo.

Another approach is to create multiple reference designs addressing different needs. QuickFilter starts by creating a generic design that it can then leverage to create a series of application-specific designs, notes Valentino.

Freescale sees a need for both educational and production-ready reference designs. “Full designs get customers to market quickly when they don’t have expertise,” says Neidig. “But for more established applications, customers have developed their expertise so they don’t need full production readiness.”

Regardless of the type of reference design that’s offered by a semiconductor vendor, developers should ensure that it has full software. “Software is a key aspect when evaluating reference designs,” says Lowe. “How much of a whole solution is the vendor providing?”

Developers should also check to make sure the reference design’s software is available for use. “We keep reminding our customers that they will need to get a license to use some of the software we include in the reference design,” says Neidig.

Finally, designers need to make sure the documentation for the reference design includes the education aspect, even when they’re adopting the design wholesale. “The reference design is not useful without documentation,” says Prakash. “It saves questions at the end.”

Documentation should include information on how to make changes, what to change, and warnings of what not to change—like high-speed circuit layouts—as well as the full details on how to fabricate the design.

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