High speed PCB signal wiring rules

High speed PCB signal wiring rules
Rule 1: High speed signal routing mask rule
In the design of high-speed PCB, it is necessary to mask key high-speed signal lines and tracking, such as clock If there is no mask or only part of the mask, EMI leakage will occur It is recommended that the shield wire be grounded with holes every 1000 mil
Rule 2: Closed loop routing rules for high-speed signals
Due to the new density of PCB boards, many PCB LAYOUT engineers are prone to make mistakes in the wiring process, that is, the clock signals and other high-speed signal networks generated when wiring multilayer PCB boards. As a result of the closed loop, such a closed loop will lead to a ring antenna, thus increasing the radiation intensity of EMI.
Rule 3: Open loop routing rules for high-speed signals
Rule 2 mentions that the closed loop of high-speed signal will cause EMI radiation, but the open loop will also cause EMI radiation. For high-speed signal networks such as clock signals, once the open-loop result is generated when wiring multilayer PCB boards, a linear antenna will be generated, thus increasing the radiation intensity of EMI.
Circuit board

Rule 4: characteristic impedance continuity rule of high-speed signal
For high-speed signals, the continuity of characteristic impedance must be ensured when switching between layers, otherwise EMI radiation will be added. In other words, the width of the wiring in the same layer must be continuous, and the wiring impedance in different layers must be continuous.
Rule 5: Regular wiring direction High speed PCB board design
The trace between two adjacent layers must follow the principle of vertical trace, otherwise it will cause crosstalk between lines and increase EMI radiation. In short, adjacent wiring layers follow the horizontal and vertical wiring directions, and vertical wiring can suppress crosstalk between lines.
Rule 6: Topology rules in high-speed PCB design
In the design of high-speed PCB, the control of characteristic impedance of PCB and the design of topology under multi load directly determine the success or failure of products. The chrysanthemum chain topology is shown in the figure, which is usually beneficial for several megahertz. It is recommended to use the rear star symmetric structure in the design of high-speed PCB boards.
Rule 7: Trace length resonance rule
Check whether the length of the signal line and the frequency of the signal constitute resonance, that is, when the wiring length is an integral multiple of 1/4 of the signal wavelength, the wiring will generate resonance, which will radiate electromagnetic waves and cause interference.
Rule 8: Return path rule
All high-speed signals must have a good return path. Make the return path of high-speed signals such as clock as small as possible. Otherwise, the radiation will increase, and the size of the radiation is proportional to the area surrounded by the signal and the return path.
Rule 9: Rules for the placement of equipment decoupling capacitors
The placement of decoupling capacitors is very important Unreasonable layout can not achieve decoupling effect at all The principle is that the smaller PCB board is surrounded by the power line and ground wire of the capacitor close to the power pin
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