Issue link: https://iconnect007.uberflip.com/i/1529118
60 DESIGN007 MAGAZINE I NOVEMBER 2024 • It's better to think of rules of thumb as guidelines rather than principles. • It's a good idea to double-check them with facts or calculations to ensure they apply to your problem. • Stay updated because some old rules might not work as technology changes. • Rules of thumb don't always consider things like cost or performance, so you should consider how they affect different parts of your project. The Best Schematic Rules of Thumb • Keep the circuit flow logi- cal and clear: Arrange the schematic so the signal flows from le to right. Inputs should be on the le, outputs on the right, and signal flow should follow a natural le-to-right pro- gression. • Use standard component symbols: Always use the correct standard symbols for components (like resistors, capaci- tors, transistors, etc.) so that anyone can quickly recognize each element. • Clearly label components and connec- tions: Every component should have a unique label (R1, C2, etc.), and all connec- tions should be clearly marked, especially power, ground, and critical signal paths. • Power and ground placement: Place power connections (VCC, +5V, etc.) at the top of the schematic and ground (GND) at the bottom. at helps make the power distribution easy to understand and trace. • Group related components: Keep com- ponents that work together (like resistors and capacitors in a filter or transistors in an amplifier) close in the schematic to clarify the relationships. • Minimize wire crossings: Avoid cross- ing wires whenever possible by rearrang- ing components or using labels for signals instead of connecting wires directly. • Use buses for complex connections: When dealing with multiple wires for sig- nals, use buses to group them and make the schematic less cluttered. Label each wire clearly to indicate where it connects. • Show power distribution clearly: Include power supply rails in a clear, easy-to- follow way. If multiple voltage levels are used (e.g., +12V, +5V, 3.3V), clearly indi- cate these and label which circuit parts use each voltage. • Indicate decoupling and bypass capaci- tors: Place decoupling capacitors close to each integrated circuit (IC) or important component and show these in the sche- matic, ensuring they are tied to the appro- priate power and ground rails. • Add test points and notes: Include test points where vital measurements might need to be taken and note any unique component values near those components, such as precision resistors or special capacitors. Component Placement Rules Of course, PCB design has many more intricate steps. Here are a few of the essen- tial rules of thumb for PCB design, focusing on placement and routing: • Group components by function: Place related components (such as resistors and capacitors for the same IC) close together to minimize routing complexity. • Place critical components first: Place key components like microcontrollers, power supplies, or high-frequency parts. Position them logically based on signal flow and power distribution. • Minimize trace lengths for sensitive signals: Place sensitive components (e.g., clocks, analog signals) close to their associated ICs to reduce noise and signal degradation.