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9 principles of high-speed automotive circuit board PCB design

Automotive circuit board PCB design and wiring principles

1. Usually, the power line and ground wire should design first to ensure the electrical performance of the circuit board. Within the scope of conditions, try to improve the width of the power line and the ground wire. It is better that the ground wire is wider than the power line, the thinnest width can reach 0.05~0.07 mm, and the power line is generally 1.2~2.5 mm. For the digital circuit, a wide ground wire can be used to form a loop, then use for a ground network (the ground of the analog circuit cannot be used in this way).

2. Layout the lines with stricter requirements (such as high-frequency lines) in advance, and avoid the adjacent parallel lines between the input end and the output end to avoid reflection interference. If necessary, ground wire isolation should be added, and the lines of two adjacent layers should be perpendicular to each other, and parasitic coupling will easily occur in parallel.

3. The oscillator case is grounded, and the clock line should be as short as possible, and should not be drawn everywhere. Below the clock oscillation circuit, the special high-speed logic circuit part should increase the area of the ground, and other signal lines should not be used to make the surrounding electric field approach zero.

4. Use 45° folded line wiring as much as possible, and do not use 90° folded line to reduce the radiation of high-frequency signals; (double arcs should be used for lines with high requirements).

5. Do not form a loop on any signal line. If it is unavoidable, the loop should be as small as possible; the vias of the signal line should be as few as possible.

6. The key lines should be as short and thick as possible, and protective ground should be added on both sides.
7. When transmitting sensitive signals and noise field band signals through flat cables, they should be led out in the way of “ground wire-signal-ground wire”.

8. Reserve a test points for key signals to facilitate production and maintenance testing.

9. After the schematic layout is complete, the circuit layout should be optimized. At the same time, after the preliminary network and DRC checking correctly, fill the non-layout area with ground wire, use a large area of copper layer for ground wire, and connect the unused places on the printed board to ground as ground line. Or design a multilayer PCB board, power supply, ground wire each occupy one layer.

Following this 9 principles, I believe that your PCB design ability will be greatly improved.