Study on Decoupling Capacitor Selection Strategy Based on Board-Level PDN Design

With the rapid development of high-speed digital circuits, the rationality of power distribution network (PDN) design is becoming increasingly critical. Among these aspects, the selection of decoupling capacitors is particularly important. Traditional methods for selecting decoupling capacitors, such as the Big "V" method and the Decade method, rely on empirical values and cannot quantitatively and accurately select capacitors. This results in high redundancy in capacitor selection, leading to wasted space on printed circuit boards (PCBs) and low decoupling efficiency, while also increasing engineering costs. This paper proposes an optimized strategy for selecting decoupling capacitors based on the frequency domain characteristics of PDN and the capacitors themselves. This strategy enables the quantitative selection of capacitors, ensuring that the number of capacitors is minimized while meeting design requirements. Additionally, simulation methods are used to confirm the reasonable placement of capacitors, leading to improved decoupling performance. The effectiveness of this strategy is validated through engineering examples, and a comparison of the number of capacitors and decoupling effectiveness before and after optimization demonstrates that the proposed strategy offers better decoupling performance, saves board space, and reduces engineering costs.