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10 PDN designers often start with a proven design. This approach has advantages, but it also has its limitations as the initial design must often be reformatted to fit into a new, often tighter, form factor. If you think of a power plane as a distributed RLC grid, by shrinking that power plane, you gain the benefit of having less parasitic effects from the power plane affect your design. In contrast, you will have higher current densities and higher power densities that you need to distribute across the board, which makes the board run hotter. In the end, you will have to reevaluate the entire design. So, while beginning with a proven design is a starting point, in the end you will still need to analyze the design from scratch and improve the PDN design to suit your application. One of the best ways to lower design cost is to minimize the spins of your board. The best way to achieve that is to have high-fidelity models of the load, the power supply, and the components in your PDN so that you can run accurate design simulations. The three key design pressures—lower cost, increased device density, and greater efficiencies—really put those component models to the test, and simulations are only as good as the models they use. Some simulations incorporate enough of the electrical parasitics or nonidealities that they are actually high fidelity and precise enough to sufficiently capture the behavior of the power solution. More simplistic models are not. To construct a power solution that is optimized for the application and minimizes board spins, you need detailed component data and tools for making high-fidelity simulations. Several technology trends are enabling denser designs. For example, increasing the converter switching frequency makes the PDN smaller, but the power converter is less efficient, which makes the boards hotter. Capacitors are trending smaller so they can be placed closer to the load and minimize parasitic loop inductance, which means that they will need to be higher quality (and more expensive) to withstand the heat. '' One challenge for PDN designers is that when using nonlinear components, you can no longer use the target impedance or other frequency domain methodologies for your design."

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