5.1. Board Design Process Overview
A typical high-speed board design begins with a product requirements document, a concept review, and a functional specification. After the specification is finalized, actual system design begins with the selection of key components. At this point, timing analysis for all the interfaces and power analysis — to determine the power requirements — is performed. Based on the power analysis, power supply modules and regulators are chosen, and a decoupling scheme is specified. Based on the timing analysis, a length-matching criterion for the buses is established. Upon completion of these tasks, as well as completion of the system design and selection of remaining components, the schematics are created. These are typically reviewed among engineers who make any necessary changes, after which they are given to the layout designer. A layout guidelines document, which specifies how to place components on the board and how to route the traces, is created and given to the layout designer as well.
A pre-layout simulation is performed to determine the ideal stack-up, trace widths, spacing, and other routing requirements. Any changes to the schematic, based on the simulation results, are incorporated in the schematic and provided to the layout designer. When the layout is complete, a post-layout simulation is performed on the critical sections of the board to ensure that there are no major signal integrity problems.
Based on the results of the post-layout simulation, any changes required are incorporated into the layout, and finally the layout is released to the fabrication house for board manufacturing. Figure 13 shows typical board design process.
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