There are many PCBs that are no longer single-function circuits (digital or analog circuits), but instead are composed of a mixture of digital and analog circuits. Therefore, it is necessary to consider the mutual interference between them when wiring, especially the noise on the ground. The frequency of the digital circuit is high, and the sensitivity of the analog circuit is strong. For the signal line, the high-frequency signal line is as far away as possible from the sensitive analog circuit device. For the ground line, the whole human PCB has only one node to the outside world, so The problem of dealing with the number and common ground of the PCB must be done inside the PCB, and the digital and analog grounds inside the board are actually separated from each other, but only at the interfaces (such as plugs) where the PCB is connected to the outside world. There is a short connection between the digital ground and the analog ground. Note that there is only one connection point. There is also no common ground on the PCB, which is determined by the system design.
The advantages of common treatment
1. Reduce the common ground impedance of analog and digital circuits
2. Eliminate clutter and reduce mutual interference
In the digital circuit, the general frequency will be higher than the frequency in the analog circuit, and their own signal will form a backflow with the ground plane (because there are various kinds of copper and copper wires in the signal transmission. Inductance and distributed capacitance. If we mix ground lines together, this reflow will crosstalk each other in digital and analog circuits. And we separate them so that they only form a backflow within themselves. They only use a zero-ohm resistor or a magnetic bead to connect because they were originally the same physical ground. Now that the wiring has separated them, they should finally be connected. If analog ground and digital ground are directly connected, mutual interference will result. Not short-circuited and inappropriate, four ways to solve this problem:
1, using magnetic beads connection;
2, with a capacitor connection;
3, use the inductance to connect;
4. Connect with 0 ohm resistor. The equivalent circuit of the magnetic beads is equivalent to a band-restricted wave limiter, which only has a significant suppression effect on the noise of a certain frequency point. It is necessary to estimate the noise frequency in advance in order to select an appropriate model. In the case of uncertain or unpredictable frequencies, the beads do not fit. Capacitors cross over and cause floating ground. The inductor has a large volume, many spurious parameters, and is unstable. The 0 ohm resistor is equivalent to a very narrow current path and can effectively limit the loop current and suppress noise. The resistance is attenuated in all frequency bands (0 Ω resistance also has impedance), which is stronger than magnetic beads.
Earphones Plug Wireless,Wireless Earphone,Earphones For Iphone,Earphone For Samsung,wireless bluetooth earphone
Shenzhen Konchang Electronic Technology Co.,Ltd , https://www.konchang.com