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6 Pushing this strategy further, however, creates a new challenge. As we move toward complete system-on-a-chip (SoC) or systems-in-a-package (SiP) components with many functions inside a single package, these components require many more power inputs. Before, we had ICs with three or four power rails. Now, we have ICs that require up to twelve power inputs to power all the SoC functions. Each branch of the power tree requires a conversion function and filtering. Other technologies and approaches can help reduce PDN size: • Power transistors and switching frequency. Increasing the hash frequency of the DC-to-DC converter enables you to reduce the size of LC filtering behind the converter, reduce the size of boost functions, and generally reduce the size of the power delivery network and passive components connected to it. Gallium nitride power transistors, which can replace silicon metal oxide semiconductor field-effect transistors, enable much higher-frequency switching with greater efficiencies, which makes it possible to avoid the use of bulk capacitors, contributing to a smaller PDN footprint. • Multiphase voltage regulators. High switching frequencies can create electromagnetic interference that can cause problems in devices with radio communications or high-performance digital signal processing. Multiphase voltage regulators reduce signal interference. They also enable more compact designs because these regulators operate with less output capacitance and greater thermal efficiency. • Modeling passive components. One challenge for PDN engineers is modeling passive components used in a PDN design simulation. In precision circuits, it's critical that values of the components be accurate. For example, a PCB can have more than twenty power rails. As we design the PDN, one way to reduce the number of conversion functions is to use filtering to separate the branches of the power tree. '' One challenge for PDN engineers is modeling passive components used in a PDN design simulation. In precision circuits, it's critical that values of the components be accurate."

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