Schematic design guidelines

Schematic contains all the necessary components for the desired circuit, and most importantly describes the connectivity between them.

Important:

• include all the necessary components (and more if applicable)
• get the connections right (main purpose of the schematic)

• Keep schematics clean, readable, and professional.
• Use mainly horizontal/vertical lines, not odd angles(45°).
• Minimize net names — connect with lines where possible.
• Group and organize components where they belong:
  • power,processing,analog,digital,outputs,inputs,electromechanical, and so on.
• Decoupling capacitors should be next to and connected to the component they are decoupling.
• Do NOT overlap symbols, lines, reference designators, values, notes or any other text.
• Keep part symbols and lines spaced clearly.
• Keep the text horizontal so whoever is reading the schematic doesn't have to hurt their neck.
• Follow conventions for power rails (positive up, ground down).
• Include board/project name, author, date, revision in the Title Block
• Leave any critical notes and design choices that others reviewing the schematic or your future self should know about without having to dive deep into the topic again and invest significant time.

• Use standardized symbols (consistent IEC/IEEE style). Resistor example: IEC elongated rectangle, IEEE zig-zag
• Label components with correct reference prefixes (R, C, L, D, Q, U, S, etc.).
• Use logical numbering schemes (by page or by block).
• Use standard, orderable values (E-series).
• Stick to one consistent naming format (e.g., 4.7k or 4K7, not both). 4K7 is preferred because its possible to not see the little dot and place a wrong value during assembly.
• Stick to one consistent value format (e.g., 100n or 0.1u, not both).

• Terminate unused inputs properly to avoid oscillation/power issues. (see course Low power design)
• Provide access pads/connectors if you may repurpose unused I/O later.
• Check datasheets for special handling of unused pins/outputs.

• Verify symbol-to-footprint pin mapping.
• Add debouncing circuits for buttons/switches where needed.

• Rectangles and titles can be added in the schematic around different functional parts i.e. Power, MCU, Outputs, Electromechanical and so on.
• Do Not Place components can be added, ex. after the board is manufactured and assembled maybe voltage divider output need to be tuned.