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Do you know what kinds of GND "ground" are in circuit design?
Date:December 8, 2024    Views:42

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.


    Ground shift phenomenon:
    Once there is a ground shift in the circuit, then the original 5V voltage may not be 5V, but become 4V. Because the 5V voltage is the reference GND ground wire 0V, if the ground shift causes the GND ground wire to rise from 0V to 1V, then the previous 5V (5V-0V=5V) voltage will become the current 4V (5V-1V=4V).

4. Power ground cable GND
    Analog ground cables AGND, digital ground cables DGND and power ground cables PGND are all classified as DC ground cables GND. These different kinds of ground wires are finally brought together as the 0V reference ground wire of the entire circuit, which is called the power ground wire GND.
    The power supply is the source of energy for all circuits. All the voltage and current required for the operation of the circuit are from the power supply. Therefore, the ground wire of the power supply, GND, is the 0V voltage reference point of all circuits.
    This is why other types of ground wires, whether they be analog ground wires AGND, digital ground wires DGND or power ground wires PGND, need to be finally converged with power ground wires GND.

5. Ac ground cable CGND
    AC ground CGND is generally found in the circuit items containing AC power supply, such as AC-DC AC to DC power supply circuit.
    AC-DC power supply circuit, divided into two parts. The front stage in the circuit is the AC AC part, and the back stage in the circuit is the DC DC part, which is forced to form two ground lines, one is the AC ground line, and the other is the DC ground line.
    The AC ground is used as the 0V reference point of the AC circuit part, and the DC ground is used as the 0V reference point of the DC circuit part. Usually in order to unify a ground wire GND in a circuit, engineers will connect the AC ground wire to the DC ground wire through a coupling capacitor or inductor.

6. Ground wire EGND
    The safety voltage of the human body is below 36V, and if the voltage exceeding 36V is applied to the human body, the human body will be damaged, which is a safety common sense of engineers in the development and design of circuit projects.
    In order to enhance the safety factor of the circuit, engineers generally use the ground wire EGND in high-voltage and high-current projects, such as household appliances, electric fans, refrigerators, television and other 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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