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- High speed PCB wiring technique of signal integrity design
- 2016-03-28 21:05:00 Read：288
- In the high-speed PCB circuit board design and manufacturing process engineers need in terms of wiring elements are arranged in a bid to ensure that the PCB has a good signal transmission integrity. In today's article, we will introduce PCB Signal Integrity Design is often used in some of the wiring tips for engineers new to you, hoping to bring some help to you daily study and work newcomers.
In the high-speed PCB circuit board design process, its cost and the number of layers of a printed circuit board, the surface area of ??the substrate is directly proportional relationship. Thus, without affecting system functionality and stability of the premise, engineers should meet as much as possible with the least number of layers the actual design needs, thereby causing the wiring density inevitably increases, and PCB layout design, the trace widths fine, the smaller the gap, the greater the crosstalk between signals, which can transmit less power. Thus, the alignment size selection must take into account various factors.
In the PCB layout design process, engineers need to follow the principles of the following main points:
First, in the wiring process designers should minimize High speed circuit device pinouts bending, using 45? Fold, reducing the coupling to external high-frequency signal reflection and mutual.
Secondly, at the time the PCB routing operation as short as possible between the designer and the lead pinouts between high-frequency circuit device pins between the alternating layers. Frequency digital signal traces should be as far as possible from analog circuits and control circuits.
In addition to the precautions mentioned above points PCB layout, in dealing with the problem of differential signals, engineers also need careful handling. Because the differential signal equal in magnitude and direction are equal, so the magnetic field is generated by two signal lines offset each other, so they can effectively reduce the EMI. Differential line spacing will often lead to changes in differential impedance, inconsistent differential impedance will seriously affect signal integrity, so the actual difference in the wiring between the two signal lines of the differential signal mutual length difference must be controlled at the rising edge of the signal time electrical length of less than 20%. If conditions permit, the differential traces must satisfy the principle of back to back, and in the same wiring layer. The difference in the wiring line spacing settings, engineers need to ensure that at least or greater than 1 times the line width. The difference between the trace and the other signal line spacing should be greater than three times the width.