Designers Corner with Prof. Mike Smith  Part 1  Part 2

Getting help

Fortunately Xilinx routinely designs and fabricates PCBs (printed-circuit boards) for testing new FPGAs. We were able to lean heavily on the people responsible for these designs in our project. We obtained a tremendous amount of help on schematic design from Bill Pabst, the Xilinx FPGA lab director, who had designed similar experimental boards. We tried to use as much as we could from these previous designs including footprints and schematic libraries. Steve Carey provided PCB layout support as an almost full-time consultant who was working on several board designs at Xilinx. In his work, both inside and outside Xilinx, Steve was familiar with high-speed layout issues that made layout of the analog section much easier.

Our contacts at Wyle were keen to help us with the layout of the board using the Level One PHY chip and the Wyle engineers provided us with some useful checks. The role of a distributor, such as Wyle, in any systems design is always an interesting one. Distributors sit between a semiconductor or chip company and the customer. They take a cut (typically 30%) for marketing and selling devices, keeping and distributing chips from their stock, and interfacing with the customer. Until recently the typical engineer’s day in the design phase of any system goes like this: you call a few distributors that you have worked with in the past to check on availability of a part and get price quotes. One of the first things they want to know is your potential application and immediately after that the potential volume. You have to be careful at this point. If you say: “I just want to prototype,” you won’t get the parts; if you say “millions,” they won’t believe you and you still won’t get the parts. If you work for a large customer and you say: “We need the parts urgently to build a prototype for a product that may go into production,” you will get parts (usually for free). Though it is hard to find exact statistics, over 90% of all boards built never go into production and the distributors know that. The distributor’s job is to find the few prototype designs that will go into production (and especially those that will go into high-volume production) and make sure that their supplier’s chips are in those systems. Distributors and FAEs (field application engineers) are rewarded handsomely for finding these “golden sockets.”

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