TEN Questions About PCB Wiring, Classic

1, what issues should pay attention about high frequency signal wiring ?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 sandwich plate.

3, if the board and add more decoupling capacitors?to say capacitance 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:0 for analog signal, this provides a complete transmission medium and impedance matching;0 to plane the analog signals and other digital signal in 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 (power IC output 5 v over a period of relatively long path to reach the MCU), or placed C power supply 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:

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, so inconclusive. In general, you can refer to the manual of the chip. ADI manuals for all hybrid chips recommend a grounding solution, some common ground, some isolated ground, depending on the chip design.

9, 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 different applications have different functions:If 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 - Ck, AGPCIK, IDE, DIMM signal lines.

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.