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50 DESIGN007 MAGAZINE I AUGUST 2025 Why Is Floor Planning So Crucial? Think of floor planning as designing the layout of a city before building its roads. A well-planned city ensures efficient traffic flow, access to utilities, and a pleasant living environment. Similarly, a well- floor-planned PCB ensures: • Optimized performance: Minimizes SI issues (reflections, crosstalk), reduces EMI, and improves power delivery • Enhanced reliability: Facilitates proper ther- mal management, preventing overheating and extending component lifespan • Improved manufacturability (design for manufacturing or DFM): Ensures compo- nents are spaced correctly for assembly, sol- dering, and testing, reducing production costs and errors • Cost efficiency: Reduces board size, layer count, and rework, directly impacting manu- facturing expenses • Simplified routing: Placing components logi- cally makes the routing phase significantly eas- ier and more efficient, reducing design time Key Considerations in Effective Floor Planning Great floor planning doesn't happen by accident. It's the result of understanding both the system- level requirements and the physical realities of PCB design. Successful floor planning requires a holistic approach, balancing numerous, often con- flicting, design constraints. Functional Partitioning and Signal Flow Start by organizing components into logical functional blocks. Place components belonging to the same functional block (e.g., CPU and its mem- ory, power supply section, RF section) nearby. This minimizes trace lengths, reduces noise, and simpli- fies routing. Define signal paths, understand the primary sig- nal flow from input to output, and arrange blocks to support a logical, unidirectional signal path, min- imizing crossovers and long, winding traces. High-speed and Critical Signals Critical signals need special attention. • Shortest path: High-speed signals (e.g., DDR, PCIe, USB 3.0) demand the shortest possi- ble trace lengths to minimize reflections and maintain SI. Place their source and destina- tion components as close as possible. • Impedance control: Consider the need for controlled impedance traces early. This influ- ences component placement to allow for uni- form trace widths and reference planes. • Differential pairs: Place components that require differential routing (e.g., Ethernet, DDR, HDMI) to allow for parallel, tightly cou- pled traces. Power Delivery Network A stable power delivery network (PDN) starts with smart placement. • Decoupling capacitors: Place decoupling capacitors as close as possible to the power pins of ICs, especially high-speed digital and analog components, to provide localized charge and to filter noise. • Power planes: Plan for efficient power and ground planes. These planes must be tightly coupled and designed in the PCB stackup as pairs, per industry best practices. Compo- nent placement should facilitate clear, unin- terrupted current return paths. • High current paths: Identify components with high current draw, such as power reg- ulators and motor drivers, and ensure that their placement allows for wide, short traces to minimize voltage drop and heat. 3 2 1