Keyword: circuit PCB, PCB design, circuit board, PCB
PCB design, rounding. PCB design is based on the graph is based on circuit principle, realize the function of the circuit designer need. The design of the printed circuit board mainly refers to the layout design, need to consider the layout of the external connections, the optimization of the internal electronic components, metal wire layout optimization and hole layout, a variety of factors such as electromagnetic protection, heat dissipation. Good landscape design can save production costs and achieve good circuit performance and heat dissipation performance. Simple layout design can be implemented by hand and complex layout design be achieved with the aid of computer aided design (CAD).
Ground wire design
In the electronic equipment on the circuit board, circuit boards, PCB, grounding is an important way to control interference. If you can combine grounding and shielding correct use, can solve most of the interference problem. Electronic equipment in the ground structure roughly systematically, casing (block), digital earth (logically) and simulation, etc. The ground should be paid attention to in the design of the following:
1. Correct selection of single point grounding and multipoint earthing
The working frequency of low frequency circuit, the signal is less than 1 MHZ, little impact on its inductance between wiring and devices, and grounding circuit had a greater influence on the formation of the circulation of interference, thus should use one-point earthing. When the working frequency of the signal is more than 10 MHZ, ground impedance becomes large, at this point should try to reduce the ground impedance, nearby multipoint earthing should be adopted. When the working frequency in 1 ~ 10 MHZ, if the grounding, the ground wire length should not exceed 1/20 of the wavelength, otherwise the multipoint earthing method should be adopted.
2. Digital circuit is separated from simulation circuit
Circuit board has both high speed logic circuit, and linear circuit, should make them apart as far as possible, and both ground not mixed, respectively connected to the power end ground. Try to increase the grounding area of linear circuit.
3. Bold grounding line as far as possible
If the ground wire is very thin, grounding potential changes over electric current, the timing signal level instability of the electronic equipment, anti-noise performance becomes bad. Therefore earth wire should be bold as far as possible, to enable it to pass three times the printed circuit board allow current. If possible, the width of the ground wire should be greater than 3 mm.
4. The ground wire road death cycle
Design only composed of digital circuit PCB ground system, the grounding wire into a dead loop can obviously improve the ability to resist noise. The reason is that there are many integrated circuit components on printed circuit board, especially in case of more components, power consumption due to limit of the grounding line thickness, can produce large potential difference on the knot, cause anti-noise ability to drop, if the grounding structure into the loop, would be to reduce the potential difference value, improve the ability to resist noise electronic equipment.
Source: //www.seekic.com
