Graphic PCB wiring digital, analog, power supply, single point grounding anti-interference !, Pcb anti-interference

Graphic PCB wiring digital, analog, power supply, single point grounding anti-interference !, Pcb anti-interference

Why do analog and digital locations have their own independent loops? Why do people share different places?The Link level is very low, and some low-level questions are often asked.
Thanks to Perter, I have learned a little about it. Now I want to share it with you.
In fact, the essence is right, that is, the numbers and analog places are both places. It's not that the two of them have a long angle on their heads. It's very strange. You need to understand why you need to separate them. First, let me tell a story.
The business building of our company is located on the third floor, the second floor is simulated, and the third floor is digital. There is only one elevator in the whole building. When there are few people at ordinary times, we can handle it on the second floor, on the third floor, there is no image of each other, but it is very difficult to go to or from work every morning. There are many people. The number of people on the third floor is always affected by the simulation on the second floor, the simulated persons on the second floor are going to go downstairs. They always have to wait for the elevator to go to the third floor. It is very troublesome to affect each other,
In order to solve this problem, the business building property has proposed two solutions,
1st million (laughing)
The elevator expands and more people can be installed,
The elevator is good, but the company will recruit more people, there are more people, then change the elevator, then recruit people... there is always an endless loop, and there is a good way to do it. Everyone simply doesn't want to take the elevator and jump down directly. No matter whether it's on the second or third floor, it will definitely solve the problem, but there will certainly be problems (1st were shot down)
2nd
Install two elevators, one on the second floor and the other on the third floor.
WondeRFul! This is so witty that the staff on the two floors will not affect each other.
End
Do you understand?

The simulated place influences each other not because it is a number or a simulation, but because they use the same elevator-location, the well used by this elevator is the ground wire we laid on the PCB.
The current of the Analog Loop follows this line, and the current of the digital loop follows this line. It is understandable that the wire is used to turn on the current, but the problem is that there is a resistance on this line!
The most fundamental problem is that the current going through this line is going to two different circuits.
Suppose there are two currents, a digital stream, and a model stream starting from the ground at the same time. There are 2 devices, several devices, and modules.
If the two circuits are not separated, the loss voltage is v when the model flow is back to the front of the grounding end of the several parts.
V = (digital stream + die stream) x wire resistance
It is equivalent to increasing the grounding end of the digital device to the ground end.
The digital device is not satisfied. I admit that it will increase a little voltage. I recognize the part of the digital stream, but why should the model stream be added to my head?
Similarly, the simulator will also complain.
2 solutions
1st: the PCB line you deploy has no impedance and will naturally not cause interference, just as the 2 and 3 floors jump down directly. That is the widest time of the well, that is, an infinite elevator can be installed. Naturally, no one will affect anyone, but everyone knows that this is mission impossible.
2nd: two circuits are separated, the number of streams and the mode stream are separated, which are separated by both the number and mode.
Similarly, although it is sometimes in a simulated loop, it must be divided into large and small current circuits to avoid mutual interference.
The so-called interference is the voltage caused by the current of two different circuits on the PCB going online. These two voltages are superimposed on each other.
OK!

When we conduct pcb cabling, we always face two or three kinds of situations on one board. The silly practice is of course, regardless of the case of November 21, copper is applied as long as it is the ground. This is not a problem for low-speed boards or boards that are insensitive to interference. Otherwise, the Boards may not work properly. Of course, if there are many places on a board, even if the Board has no requirements, but from a rigorous and serious point of view, we still need to use the method mentioned in this article to wiring, to optimize the entire system and maximize its performance! Of course, I will not talk about some basic concepts of these regions and why they should be separated. If you don't understand them, check them yourself!

Finally, there are also many posts on the Internet about this issue, but most of them are text descriptions and no illustrations, which make people feel that they have always known but do not know why, in this bold illustration, I want to give my thoughts. If not, I hope you can give me some advice and leave a message. Thanks ~

 

1. Digital, analog, and power supply on the Board:

From this figure, we can see that the analog and digital locations are completely separated, and finally each point is connected to the power source, which can prevent the mutual Crosstalk of the ground signal from affecting some sensitive components, as we all know, digital components have a higher Interference tolerance than analog components, while the noise on the digital ground is generally large, so separating them can reduce this effect. In addition, the single point grounding position should be as close as possible to the inlet of the power source (initial position) of the Board, so that the interference can be minimized by the principle that the current is always returned by the shortest short-circuit runoff.

 

2. Only digital and power sources are available on the Board:

From this figure, we can see that only a single point of grounding, such as 0 euro resistance or magnetic beads, can be used between the power source and the digital ground, similarly, the single point grounding position should be as close as possible to the entry of the Board power source location (start position ).

Iii. display the pcb system I have drawn (in the second case ):

1. Ground Partitioning

2. 0 euro resistance Single Point Grounding

3. Front View

Summary: The diagram in this article is very suitable for the pcb ground layout of the single-chip microcomputer control system. Other systems can also be referred!