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How to control EMI radiation by PCB layered stack?About 4Layer.
-The first is the preferred solution. The outer layer of PCB is stratum, and the middle two layers are signal/power layer.The power supply on the signal layer is wired with a wide line, which makes the path impedance of the power current low and the path impedance of the signal microstrip low.From EMI control point of view, this is the best available 4-layer PCB structure.
-In the second way, the outer layer is power supply and ground, and the middle layer is signal.Compared with the traditional 4-layer plate, the improvement of the scheme is smaller, and the inter-layer impedance is as poor as the traditional 4-layer PCB.
-If the routing impedance is to be controlled, the stacking schemes described above must carefully place the routing beneath the power and grounding copper island.In addition, the power supply or copper laying islands in the formation should be interlinked as much as possible to ensure DC and low frequency connectivity.
