PCB design is very important in the process of the printed circuit board, which determines the whole basis of PCB. Here are some summarized points of PCB design that need to pay attention to:
1. Choose PCB board:
The choice of PCB board must strike a balance between meeting design requirements, mass production, and cost. The design requirements include both electrical and mechanical parts. Generally, material problems are more serious when designing very high-speed PCB boards (frequency bigger than GHz)
2. Avoid high-frequency interference:
The basic idea to avoid high-frequency interference is to minimize the electromagnetic field interference of high-frequency signals, which is called crosstalk (Crosstalk). It can increase the distance between high-speed signals and analog signals to avoid crosstalk.
3. Solve the problem of signal integrity:
Signal integrity is basically a problem of impedance matching, and the factors that affect impedance matching include the structure and output impedance of the signal source, the characteristic impedance of the trace, the characteristics of the load, and the topology of the trace. The solution is to rely on termination and adjustment of the routing topology.
4. Realize differential wiring method:
There are two points to pay attention to in the layout of the differential pair. One is that the length of the two wires should be as long as possible, and the other is that the distance between the two wires (the distance is determined by the differential impedance) must be kept constant, that is, to keep parallel. There are two ways to go, one is that the two wires go on the same wiring layer (side-by-side), the other is that the two wires go on two adjacent layers above and below (over-under)
5. In the case of a clock signal line with only one output terminal, it only means that both the signal source and the receiving terminal are differential signals, so that differential wiring cannot be used for a clock signal with only one output terminal.