PCB News - How to reduce the impact of high-speed PCB crosstalk

How to reduce the impact of high-speed PCB crosstalk

Crosstalk is ubiquitous inhigh-speed and high-density PCB design, and the impact of crosstalk on the system is generally negative. In order to reduce crosstalk, the most basic thing is to make the coupling between the interference source network and the interfered network as small as possible. It is impossible to completely avoid crosstalk in high-density and complex PCB design, but in system design, designers should choose appropriate methods to minimize crosstalk without affecting other performance of the system. Combined with the above analysis, the solution to the crosstalk problem is mainly considered from the following aspects:

1) When the wiring conditions allow, increase the distance between the transmission lines as much as possible; or reduce the parallel length between adjacent transmission lines as much as possible (cumulative parallel length), preferably routing between different layers.

2) The signal layer (no plane layer isolation) of the two adjacent layers should be perpendicular to the routing direction, try to avoid parallel routing to reduce crosstalk between layers.

3) Under the condition of ensuring signal timing, choose devices with low conversion speed as much as possible to slow down the rate of change of electric field and magnetic field, thereby reducing crosstalk.

4) When designing the stack, under the condition of satisfying the characteristic impedance, the dielectric layer between the wiring layer and the reference plane (power or ground plane) should be made as thin as possible, thus increasing the coupling between the transmission line and the reference plane and reducing Coupling of adjacent transmission lines.

5) Since the surface layer has only one reference plane, the electric field coupling of the surface layer wiring is stronger than that of the middle layer, so signal lines that are more sensitive to crosstalk should be placed in the inner layer as much as possible.

6) Through termination, the impedance of the far end and near end of the transmission line can be matched with that of the transmission line, which can greatly reduce the amplitude of crosstalk.

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