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锘? If the high-speed PCB Schematic design to the node as the connection as simple and as seen on the computer monitor as beautiful then Seahawks Doug Baldwin Jersey , it will be a wonderful thing. However, unless the designer first joined the PCB design, or extremely lucky, the actual PCB design they are usually not as easy as in the circuit design. Eventually work in the design, make sure it was before the performance, PCB designers are facing many new challenges. This is the current status of high-speed PCB design - design rules and design the continuous development of guidelines, if lucky, they will form a successful solution. PCB is proficient in most of the working principle of the device PCB and interaction and composition Board Input and output of various data transmission standard schematic designers and may know little or even do not know, the little diagram printed circuit copper wire connection into what will happen to each professional layout designer Cooperation Results. Typically, the final success or failure of the board is responsible for schematic design. However, the schematic design for excellent technical know the territory the more chance to avoid the more major issues. If the design contains high-density FPGA Seahawks Russell Okung Jersey , is likely to be many challenges placed in front of well-designed schematics. Including hundreds of input and output quantity, more than 500MHz (some designs may be higher) operating frequency, and small to semi-mm ball pitch, all of which will lead to the design unit should not be created between interaction. Concurrent Switch Noise First challenge is likely that the so-called concurrent switching noise (SSN) or complicated switching output (SSO). A large number of frequency data stream will generate ringing and crosstalk data lines like problem Power supply And ground plane will also appear on the performance impact of the circuit board ground bounce and power supply noise. Order to solve the high-speed data lines ringing and crosstalk, differential signal switch is a good first step. As the differential pair on a line is the absorption (Sink) side, providing another source of current, inductive effects can be eliminated. Transmit data using differential pair, because the current kept at the local, thereby helping reduce the return path of the induced current produce a "bounce" noise. For up to several hundred MHz or even GHz radio frequency, signal theory shows that in impedance matching the maximum signal power can be transmitted. The transmission line matching bad, will have a reflection Seahawks Earl Thomas III Jersey , only part of the signal transmitted from the originator to the receiving device, while other parts of the transmitter and the receiver in the back and forth between the rebound. Differential signal on the PCB to achieve the good and bad will have impedance matching (and other) play a significant role. Design differential traces Differential alignment design based on the principle of impedance controlled PCB. The model somewhat like coaxial cable. In the impedance controlled PCB, metal surface layer can be used as shield, insulator is FR4 laminate, the conductor is the signal trace on (see Figure 1). FR4 dielectric constant at the average between 4.2 to 4.5. Manufacturing error because they do not know, it may lead to excessive copper etching, eventually leading to resistance error. PCB trace impedance calculation of the most accurate method is the use of field analytical procedures (usually two-dimensional, sometimes three-dimensional), it needs to use the finite element solution to the entire PCB bulk Maxwell's equations directly. The software can take the line spacing, line width, line thickness and the insulation effect of the height to analyze the EMI. Figure 1: Comparison of coaxial cable and the PCB. 100 differential characteristic impedance of cable has become the industry standard for value. 100 differential lines can be two equal length 50 single-ended line of production. As the two traces close to each other Derrick Coleman Jersey , the line will reduce the coupling between the differential mode impedance line. In order to maintain the impedance of 100 , and take line width must be decreased a little. The results, 100 differential lines on each thread of common mode impedance slightly higher than 50 euro. Theory traces the size and materials used in the decision of the impedance, but the through-hole, Connector And even the device pad will be introduced in the signal path impedance discontinuities. These things do not usually impossible. Sometimes, in order to more rational layout and routing, we need to increase the number of layers PCB, or add features such as buried vias. Buried via connections only part of PCB layers, but in solving the transmission line problem, the board also increased the production cost. But sometimes there is no choice. As the signal faster and faster, smaller and smaller spaces Cliff Avril Jersey , such as on the buried hole began to increase the additional demand, which should be the cost of the solution PCB elements. Figure 2: Differential line design example. Shown in Figure 2 is the actual differential cross-section line of the territory of the most common pattern. The use of stripline wiring, the signal is FR-4 material in the middle. The microstrip line, a conductor is exposed in the air. Because the lowest dielectric constant of air (Er = 1), it is most suitable for laying some of the key top-level signals such as clock signal or high frequency SERial-DESerial (SERDES) signal. Wiring should be coupled to the microstrip ground plane below the ground plane through the absorbing part of the electromagnetic field lines to reduce electromagnetic interference (EMI). In the strip line, all coupled to the electromagnetic field lines above and below the reference plane, which greatly reduces EMI. , If possible, should try not to use the broadside-coupled stripline design. This structure vulnerable to reference plane in the coupling of the differential noise..