Technical
PCB related knowledge- The purpose of each layer of the PCB
How to do heat resistance testing for PCB board
Detailed explanation of rigid-flex board and IC carrier board
PCBA prototype procedure
Defects which can be detected by the SPI
What are the spacing requirements for designing PCB circuit boards?
What are the classification and advantages of PCB metal substrates?
Difference between the processing technology of 1Layer AL PCB and 2Layer AL PCB
Introduction of FPC Cable and its usage
advantages of Shenzhen SMT assembly factory
inspection items before PCB ordering
usages of ceramic substrates
main applications of PCB boards
Cost-effective PCB product services
How to check short circuit of a circuit board during manual soldering
Identify the polarity of electronic components during PCBA processing
Means Which Can Prevent Component Shifting in SMT Processing
Skills of PCB prototype manual soldering
Reasons for the shift of Components in the SMT Process
Seven Types of PCB Probes
What Should Be Paid Attention to in Layout of High-frequency PCB
Precautions for PCB CCL Selection
Advantages of LED Plant growth light
Advantages of using LED grow lights to grow industrial hemp
Detailed explanation of PCB manufacturing process and precautions
Detailed explanation of PCB manufacturing process and precautions
How to draw multilayer PCB on Altium Designer
Three basic elements of interference and how to suppression them.
Decrease interference between digital circuit and analog circuit
SMT Component Placement Process Of Parts : Manual Placement
SMT factory incoming PCB material inspection
Basic concepts commonly used in PCB design
Ideas and principles of High speed PCB layout
Component layout rules and safety distance considerations
SMT assembly process quality specification
5 points in PCB layout
Professional interpretation of SMT
Advantages and disadvantages of different PCB surface treatment
Special process in PCB prototype
Why the via hole become open after component assembly
Keep the cost of the PCB as low as possible
what are the causes of PCB board heating radiation problem
Pad size and via diameter dimensions consideration in PCB prototyping
How to Judge the Acceptance of PCB Quality
Which Color Circuit Board Sells the Most Expensive
Method to Solve the Noise Interference of Power Supply on High-frequency PCB Board
Disassembly Skills of Chip Components on PCB
What Factors Should Be Considered in the Selection of High-frequency PCB CCL
How to Place Special Components during PCB Layout
What Are the Functions of Capacitors in Circuits?
Testing Techniques for Common Electronics Components
What to do if There is a Short Circuit on the PCB
Desoldering Principles and knowhow during PCBA Processing
Black Oxidation of the Inner Layer of the Multilayer PCB
How to Ensure the High-performance Design of PCB
What Is the Printing Process of SMT Solder Paste?
PCB without fiducial mark, Is There Any Way to do SMT for It
What Are the Benefits of Reserving Break-up Tab for PCB Production
How Does SMT Affect PCB Production Time and Speed It Up
Classification of PCBs from three aspects
Common Problems and Solutions for Dry Film pasting during PCB Manufacturing process
Several Elements to Inspect after PCB Design
What is a halogen-free circuit board?
What Do Capacitive Coupling and Decoupling Mean?
What Are the Differences Between PCB Paste Mask and Solder Mask?
How PCBA Is Packaged and Shipped
How long can PCBA finished products be stored?
What Are the Differences and Relations Between PCB, PCBA, and SMT?
PCB Baking Specifications
PCB "Solder Mask Tenting" and "Solder Mask Opening"
Five reasons for PCB deformation and six solutions
Importance of first article inspection of PCBA board
Temperature zone standard for SMT reflow soldering
Small and medium volume PCB manufacturers in China
The main reason for PCBA cleaning
For power filter, the more capacitors, the better?
What does PCBA programming mean?
Content of PCB incoming testing
What conditions must be met for PCB circuit board soldering?
What is Blind via and Buried via
PCBA Manufacturers Temperature and Humidity Sensitive Components Management
Why choose Shenzhen SMT processing factory?
How long does it take to calculate the quotation for PCBA manufacturing?
Introduction of PCB design clearance requirements
Explanation of BOM, DIP, SMT, SMD
Introduction of the process of PCBA prototype
How to prevent pseudo soldering or cold soldering defects in PCBA manufacturing?

Classification of different GND in circuit

Ask a simple but difficult circuit question: What is the nature of the ground in the circuit?
During the PCB Layout process, engineers will face different GND treatments. Why is this? In the circuit schematic design stage, in order to reduce the mutual interference between circuits, engineers generally introduce different ground as 0V reference points for different functional circuits to form different current loops.

Classification of GND
1. Analog ground, AGND
The analog ground AGND is mainly used in the analog circuit part, such as the ADC acquisition circuit of the analog sensor, the operational amplification circuit and so on.
In these analog circuits, since the signal is an analog signal, it is a weak signal, and it is easily affected by the large current of other circuits. If they are not distinguished, a large current will produce a large voltage drop in the analog circuit, which will cause the analog signal to be distorted, and severely may cause the analog circuit to fail.

2. Digital ground, DGND
The digital ground DGND, obviously opposite to the analog ground AGND, is mainly used for digital circuit parts, such as button detection circuit, USB communication circuit, MCU circuit and so on.
The digital ground DGND is set up because digital circuits have a common feature, they are all discrete signals, and only the digital "0" is distinguished from the digital "1", as shown in the figure below.



In the process of changing from the digital "0" voltage to the digital "1" voltage, or changing from the digital "1" voltage to the digital "0" voltage, the voltage has a change. According to Maxwell's electromagnetic theory, a magnetic field is generated around the changing current, which forms EMC radiation to other circuits.
In order to reduce the EMC radiation effect of the circuit, a separate digital ground DGND must be used to effectively isolate other circuits.

3. Power ground PGND
Whether analog ground AGND or digital ground 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, which is called the power ground PGND.

High-power circuits, as the name suggests, are circuits with relatively large currents. Obviously, a large current can easily cause ground offsets between circuits with different functions, as shown in the figure below.


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

4. Power ground GND
The analog ground AGND, the digital ground DGND and the power ground PGND are all classified as the DC ground GND. These different types of ground s are finally brought together to serve as the 0V reference ground of the entire circuit. This ground is called the power ground GND.

The power supply is the energy source of all circuits. The voltage and current required by all circuits are from the power supply. Therefore, the ground line GND of the power supply is the 0V voltage reference point for all circuits.

This is why other types of ground, whether it is analog ground AGND, digital ground DGND or power ground PGND, need to be collected together with power ground GND in the end.

5. AC ground CGND
The AC ground CGND generally exists in a circuit project that contains AC power, such as an AC to DC power supply circuit.
The AC-DC power supply circuit is divided into two parts. The front-end circuit in the circuit is the AC part, and the back-end circuit in the circuit is the DC part. This is forced to form two ground s, one is the AC ground and the other is the DC ground.

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 GND in the circuit, engineers will connect the AC ground to the DC ground through a coupling capacitor or inductance.

6. Earth ground EGND
The safety voltage of the human body is below 36V. If a voltage exceeding 36V is applied to the human body, it will cause damage to the human body. This is a common safety sense that engineers keep in mind when develop and design circuit projects.

In order to enhance the safety factor of the circuit, engineers generally use the EGND in high-voltage and high-current projects, such as in the circuits of household appliances, electric fans, refrigerators, and televisions. The socket with earth ground EGND protection function, as shown in the figure below.


Why the sockets of household appliances are 3 terminals? 220V AC only needs live and neutral wires, two wires are enough. There are three connection terminals of the socket, two of which are used for 220V live and neutral, and the other terminal is the earth ground EGND for protection.

What needs to be pointed out is the earth ground EGND, which is only connected to our earth and plays a high-voltage protection function. It does not participate in the circuit function of the project and has nothing to do with the circuit function. Therefore, the EGND has circuit meanings that are obviously different from other types of GND.