What is the nature of GND, the ground wire in the circuit? Is to provide a low impedance circuit for the circuit;
At the same time, in the process of PCB Layout, engineers will face different GND ground lines.
Why is that?
In the circuit principle design stage, in order to reduce the mutual interference between circuits, engineers generally introduce different GND ground lines as 0V reference points for different functional circuits to form different current loops. Next let's look at the different types of GND
Classification of GND ground cables
1. Analog ground wire AGND
Analog ground wire AGND, mainly used in analog circuit parts, such as analog sensor ADC acquisition circuit, operation amplification circuit and so on.
In these analog circuits, because the signal is an analog signal, it is a weak signal and is easily affected by the large current of other circuits. If not distinguished, the high current will produce a large voltage drop in the analog circuit, which will cause the analog signal distortion, and may seriously cause the analog circuit function failure.
2. Digital ground cable DGND
Digital ground wire DGND is obviously relative to analog ground wire AGND, which is mainly used in digital circuits, such as key detection circuit, USB communication circuit, MCU circuit and so on.
The reason why the digital ground wire DGND is set up is because the digital circuit has a common characteristic, which is a discrete signal, only the digital "0" and the digital "1" distinguish.
Digital signal:
In the process of jumping from a digital "0" voltage to a digital "1" voltage, or from a digital "1" voltage to a digital "0" voltage in the process of a change in voltage, according to Maxwell's electromagnetic theory, the changing current will generate a magnetic field around, which will form EMC radiation to other circuits.
In order to reduce the EMC radiation impact of the circuit, a separate digital ground wire DGND must be used to allow other circuits to be effectively isolated.
3, power ground PGND
Analog ground wire AGND or digital ground wire DGND, they are both low-power circuits. In high-power circuits, such as motor drive circuits, solenoid valve drive circuits, etc., there is also a separate reference ground wire, which is called power ground wire PGND.
High-power circuit, as the name suggests, is a relatively large current circuit. It is obvious that the large current is easy to cause the ground shift phenomenon between different functional circuits.
Socket with EGND protection
The socket for household appliances, why are there 3 terminals? 220V AC only needs live wire and neutral wire, two can, then why is the socket 3 terminal?
The three wiring terminals of the socket, of which two terminals are used for 220V live wire and neutral wire, and the other terminal is the ground wire EGND that plays a protective role.
The chip brother needs to point out that the ground wire EGND is only connected to our earth and plays a high-voltage protection role. It does not participate in the circuit function of the project and has nothing to do with the circuit function.
Therefore, EGND ground wire has obvious difference in circuit meaning from other types of ground wire GND.
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