20 questions about PCB wiring, classic

                               20 questions about PCB wiring, classic

    1, high frequency signal wiring should pay attention to what issues?Line impedance matching; With other signal space isolation; For high frequency signal, the differential line effect will be better.

    2, when the cloth plate, if line, hole could, of course can affect electrical properties of the board, how to improve the electrical performance of the board?For low frequency signal, via it doesn't matter, the high frequency signal to minimize the hole. If the line can consider more multilayer board,

    3, if the board and add more decoupling capacitors?Decoupling capacitor to be in the right place to add the appropriate value. For example, power supply port will need to add in the simulator, and the need to use different capacitance value to filter out the spurious signals of different frequency.

    4. A good standards of board it is?Layout is reasonable, the power cord power redundancy, high frequency impedance, low frequency line concise enough.

  5. Hole and blind hole signal differences influence have how old? What are the principles of the application?Using blind or buried hole is to improve the density of sandwich plate, reducing the layer number and panel size, and greatly reduce the number of the plating through hole.

  But in comparison, the hole on the process for implementation, low cost, so generally are used in the design of the hole.

    6, when it comes to analog digital hybrid system, it is suggested that electric layer division, take the whole piece of copper ground plane, also it is suggested that electric strata are divided, different in power supply terminals, but the signal return path is so far, specific application should be how to choose the right method

If there is a high frequency > 20 MHZ signal lines, and the length and the quantity are more, so need at least two layers for the high frequency signal. A layer of signal lines, a layer of large area, and signal lines need to make enough layer of hole to the ground. This is the purpose of:

   For analog signal, this provides a complete transmission medium and impedance matching;. The ground plane analog signals and other digital signal isolation. Loop is small enough, because you have played a lot of holes is a big plane.

    7, in the circuit board, signal input plugin in the far left along the PCB, MCU on the right, so when the layout is regulated power supply chip is placed in the source close to the connector (5 v power supply 1 c output over a period of a long path to reach MCU), or placed the power 1 c to the centre-right (power IC output 5 v line to MCU is short, but the input power line segment after a relatively long period of PCB)? Or have a better layout?

   The first signal input plugin is a simulator? If you advise power simulator, the layout should try not to affect the analog part of the signal integrity. So there are a few points to consider:

    First regulated power supply chip is cleaner, ripple small power supply? Analog part of the power supply, the requirement to the power supply is higher;

    Analog part and MCU is a power, in the design of high precision circuit, suggest to separate analog and digital part of the power supply;

For digital part of the power supply need to be considered to minimize the impact on the analog circuit part.

     8, in the application of high-speed signal chain, for the ASIC are more analog ground and digital ground, is used to break up, or not split? Both the rule is? Which is better?So far no conclusion. Under normal circumstances can refer to the manual chip. ADI mixed all chip in the manual of a grounding scheme is recommended, some are recommended to, some recommendations about isolation, depending on the chip design9, when want to consider the length of the line? If you want to consider using for the long term, such as the difference in length between two signal lines can't more than how much? How to calculate?Difference method: if a sine signal, the length difference is equal to half of its transmission wavelength, phase difference is 180 degrees, the two signals is then completely offset. So when the length of the poor is a maximum. By analogy, signal difference must be less than this value.10, high-speed the serpentine line, suitable for what kind of situation? What are the disadvantages? For difference go line, for example, requires two sets of signals are orthogonal.Snake walk the line, because of the different applications have different effectsIf serpentine line appear in the computer board, its main play the role of a filter inductor and impedance matching, is used to improve the anti-interference ability of the circuit. In computer motherboard, serpentine line, mainly used in some of the clock signal, such as PCI - Clk, AGPCIK, IDE, DIMM signal lines, etc.If in the ordinary PCB, besides have the function of the filter inductance, also can be used as a radio antenna inductance coil and so on. Such as 2.4 G radio is used for inductance

    If in the ordinary PCB, besides have the function of the filter inductance, also can be used as a radio antenna inductance coil and so on. Such as 2.4 G radio is used for inductance.Must be strict with some signal wiring length, high speed digital PCB line length is such as to keep the signal delay differential in a range, to ensure the effectiveness of the read data in the system in the same period (delay less than one clock cycle wrong when they read the data of the next cycle). Such as INTELHUB HUBLink in architecture, a total of 13 root, using the frequency of 233 MHZ, must strict isometric, to eliminate the delay caused by the hidden trouble, winding is the only solution to the general request delay no more than a quarter of the clock cycle, unit length line delay difference is fixed, delay with the line width, line length, copper layer thickness, plate structure , but the line is too long will increase the distribution of distributed capacitance and inductance, make the signal quality declined. So the clock IC pins are generally after termination, but serpentine line is not the inductance of the role. On the contrary, the inductance will make up along the higher harmonic signals in phase shift, cause the signal quality deterioration, serpentine line spacing is required at least is the line width of the two. The smaller the rise time of a signal, the more vulnerable to the influence of the distribution capacitance and inductance.Snake go line in some special circuit plays the role of a distribution parameter of the LC filter.

   If in the ordinary PCB, besides have the function of the filter inductance, also can be used as a radio antenna inductance coil and so on. Such as 2.4 G radio is used for inductance.Must be strict with some signal wiring length, high speed digital PCB line length is such as to keep the signal delay differential in a range, to ensure the effectiveness of the read data in the system in the same period (delay less than one clock cycle wrong when they read the data of the next cycle). Such as INTELHUB HUBLink in architecture, a total of 13 root, using the frequency of 233 MHZ, must strict isometric, to eliminate the delay caused by the hidden trouble, winding is the only solution to the general request delay no more than a quarter of the clock cycle, unit length line delay difference is fixed, delay with the line width, line length, copper layer thickness, plate structure , but the line is too long will increase the distribution of distributed capacitance and inductance, make the signal quality declined. So the clock IC pins are generally after termination, but serpentine line is not the inductance of the role. On the contrary, the inductance will make up along the higher harmonic signals in phase shift, cause the signal quality deterioration, serpentine line spacing is required at least is the line width of the two. The smaller the rise time of a signal, the more vulnerable to the influence of the distribution capacitance and inductance.Snake go line in some special circuit plays the role of a distribution parameter of the LC filter.

    Rf race with 12, can you tell me the PCB circuit transmission line design do you have any need to pay attention to? The transmission line hole how to set up a more appropriate, impedance matching is the need to design PCB processing factory or want to work with?This problem should consider many factors. The various parameters of the material such as PCB finally established transmission line model based on these parameters, the parameters of the device, etc. Impedance matching typically to be designed in accordance with the information provided by manufacturer.

   13, in analog circuits and digital circuits, such as half of the FPGA digital circuit or part, the other is analog part of the DAC and the relevant amplifier. All kinds of voltage of power supply is more, have both analog voltage value of power supply circuit are used, whether can use a common power supply, decorate in the wiring and magnetic beads on what skills?Such use is not recommended, so use will be more complex, also hard to debug.

    14, in the high-speed multi-layer PCB design, about resistance capacitance devices such as the choice of encapsulation, what is the main basis? Which is commonly used packaging, can give a few examples.0402 is a commonly used mobile phones; 0603 is a commonly used high speed signal module; Is based on the packaging is smaller, the smaller the parasitic parameters of course different manufacturers of the same package, there is much difference in the high frequency performance. I suggest you use the special components of high frequency in key position.

   15, a double panel is go first line in the design or go first ground?This should be considered. In considering the layout of the case, first consider the line.16, in the high-speed multi-layer PCB design, the most should pay attention to is the problem? Can do detailed solution of the problemSignal lines, the best is it should be noted that the design, the power cord, ground, the line of control that you is how to divide in each layer. The general principle is analog signal and analog signal to ensure at least a separate layer. Power supply is also suggested by a single layer.When 17, can you tell me the specific use 2 layer board, 4 layer board, 6 layer board? Have strict limits on technology (minus volume)? Is subject or its a CPU frequency and the frequency of the external data interaction device shall prevail?Using sandwich plate can provide complete ground plane first, also can provide more signal layer, convenient line. For the CPU to control the application of external storage devices, should be taken into account for the frequency of interaction, if the frequency is higher, complete ground plane is make sure, in addition line is best to keep the isometric.18, PCB wiring on how to analyze the influence of analog signal transmission, noise is introduced in the process of how to distinguish the signal transmission, as a result of or op-amp device wiring?This is very difficult to distinguish, only by introducing additional noise PCB wiring to avoid wiring.19, for high-speed multi-layer PCB, power cord, ground and signal line width is set to how much is appropriate, what is the common setting, can illustrate? Such as working frequency in how to set up 300 MHZ?300 MHZ signal must do impedance line width and line and simulation calculation of the distance; The power cord need to decide the size of the current line width, at the time of mixed-signal PCB generally don't have to indicate to the "line", but with the entire plane, so as to guarantee the minimum loop resistance, and below the line has a complete plane

    The layout of the 20, how to achieve the best cooling effect?The source of heat in PCB mainly has three aspects: the electronic components of fever; The PCB itself fever; Other parts from the heat.In these three heat source, the components of calorific value is the largest, is the main heat source, followed by the heat generated in PCB, external incoming heat depends on the overall system thermal design, do not do temporarily consideration.So hot design purpose is to take the appropriate measures and methods to reduce the temperature of the components and the temperature of the PCB board, make the system work properly under the right temperature. Mainly by reducing fever, and speed up the heat.