In the process of PCB layout and routing, it is crucial to follow certain design guidelines to ensure the stability and reliability of the circuit. Below are 20 essential PCB layout design guidelines that we hope will be helpful to everyone.
1. Isolation of Strong and Weak Currents, High and Low Voltages, and High and Low Frequencies
During layout, circuits with strong and weak currents, high and low voltages, and high and low frequencies should be separated to avoid mutual interference. The boundary standard is usually a difference of one order of magnitude, and isolation methods can include spatial separation or grounding separation;
2. Layout and Routing of Crystal Oscillators
Crystal oscillators should be placed as close to the IC as possible, and the routing should be wide to reduce noise interference and signal loss;
3. Separation of Analog and Digital Circuits
Analog and digital circuits should have their own power and ground paths to reduce mutual interference. Where possible, the power and ground paths for these two parts of the circuit should be widened or separate power and ground layers should be used;
4. Layout and Routing of Clocks
When clock routing passes through connectors, ground pins should surround the connector pins to reduce electromagnetic radiation and interference;
5. Grounding of Crystal Oscillator Casings
To improve stability, the casing of the crystal oscillator should be grounded to eliminate potential electromagnetic interference;
6. Layout of High-Speed, Medium-Speed, and Low-Speed Circuits
When mixing high-speed, medium-speed, and low-speed digital circuits, different layout areas should be allocated on the printed circuit board to reduce mutual interference;
7. Separation of Power and Ground on the Motherboard
If the PCB is inserted into a motherboard, the power and ground for the analog and digital circuits on the motherboard should also be separated and grounded at the motherboard’s grounding point;
8. Separation of Low-Level Circuits
Low-level analog circuits and digital logic circuits should be separated as much as possible to reduce noise and interference;
9. Connection of Analog and Digital Grounds
The analog and digital grounds of a standalone PCB can be connected at a single point near the system grounding point. If the power supply voltages are consistent, the power supplies for the analog and digital circuits should connect at the power entry point; if inconsistent, a capacitor of 1~2nF should be placed near the two power supplies to provide a return current path for the signal;
10. Power Plane Design for Multilayer Boards
In multilayer printed circuit board design, the power plane should be close to the ground plane and arranged beneath the ground plane to improve electromagnetic compatibility.
11. Routing Layers Adjacent to Metal Planes
Routing layers should be arranged adjacent to solid metal planes to provide good shielding effects;
12. Layer Separation for Digital and Analog Circuits
In multilayer printed circuit board design, digital and analog circuits should be separated. If they need to be arranged on the same layer, isolation methods such as trenches and additional grounding lines should be used;
13. Isolation of Clocks and High-Frequency Circuits
Clock circuits and high-frequency circuits are major sources of interference and should be arranged separately, away from sensitive circuits;
14. Right-Angle Routing
Interference source lines and sensitive lines should be routed at right angles as much as possible to reduce coupling;
15. Minimize Loop Area
Minimize the loop area between interference sources and sensitive circuits, using twisted pairs and shielded cables to reduce electromagnetic radiation and interference;
16. Attention to Waveform Distortion in Long-Line Transmission
During long-line transmission, attention should be paid to waveform distortion issues to ensure signal quality;
17. Increase Line Spacing
Increase the spacing between lines to reduce mutual inductance and lower coupling effects between lines;
18. Increase Line Distance
Increasing the distance between lines is an effective method to reduce capacitive coupling;
19. Classification and Bundling of Lines
Before formal routing, lines should be classified by power level and bundled separately to reduce interference;
20. Spacing for Classified Lines
Wires of different classifications should be laid out separately, maintaining a minimum distance, typically 50~75mm, to ensure the stability and reliability of the circuit.
This article is an original piece by Wanyi Education. Please indicate the source when reprinting!