1. To mitigate the edge radiation effect, electromagnetic interference is emitted from the edges of the board. By retracting the power layer so that the electric field is confined within the grounding layer, the overall EMC performance is significantly improved. For instance, if you reduce the power layer by 20H, around 70% of the electric field can be confined to the ground edge; reducing it by 100H can limit up to 98% of the electric field.
2. The ground plane should be larger than the power or signal layers to effectively reduce external radiation interference and shield the board from outside disturbances. In typical PCB design, shrinking the power layer by 1mm from the ground layer generally satisfies the 20H principle.
3. How to apply the 3W and 20H principles in PCB design?
The 3W principle is straightforward to implement in PCB design. Ensure that the center-to-center distance between traces is at least three times the trace width. For example, if the trace width is 6 mils, the center-to-center spacing should be set to 18 mils.
To meet the 3W principle in Allegro, set the line-to-line clearance rule to 12 mils, as the software calculates spacing based on the edge-to-edge distance.
4. As for the 20H principle, to implement it in PCB design, it is generally necessary to reduce the power layer by 1mm from the ground layer when dividing the plane layers.
Then, punch a shielding ground via on the 1mm shrink tape, with one 150mil via.
3. **What are the types of PCB signal lines and what are the differences?**
PCB signal lines are typically categorized into two types: microstrip lines and strip lines.
A microstrip line is a type of stripline that is placed on the surface layer (microstrip) and is attached to the top layer of the PCB. As illustrated below, the blue section represents the conductor, the green section is the insulating dielectric of the PCB, and the blue block on top is the microstrip line. Since one side of the microstrip line is exposed to air, it can radiate energy or be susceptible to interference from surrounding radiation, while the other side is in contact with the insulating dielectric of the PCB. Consequently, part of the electric field formed by the microstrip line is distributed in the air, and the other part is confined to the PCB’s insulating medium. The main advantage of microstrip lines is that they offer faster signal transmission speeds compared to striplines.
The stripline, or double stripline, is placed in the inner layers of the PCB and is embedded between two conductive layers. As shown in the diagram below, the blue part is the conductor, the green part is the insulating dielectric, and the stripline is embedded between two conductive planes. Since the stripline is sandwiched between two conductor layers, its electric field is confined within these two conductive planes, preventing energy radiation and shielding it from external interference. However, because the stripline is surrounded by dielectric material (with a dielectric constant greater than 1), the signal transmission speed in a stripline is slower than in a microstrip line.
4. **What is EMC?**
EMC stands for Electromagnetic Compatibility, referring to the ability of a device or system to operate properly in its electromagnetic environment without causing or suffering from harmful interference.
For sensors, electromagnetic compatibility refers to the sensor’s ability to function correctly in an electromagnetic environment while maintaining its inherent performance and meeting its specified functions. EMC for sensors includes two key requirements: First, the electromagnetic interference (EMI) generated by the sensor during normal operation should not exceed certain limits; second, the sensor should have sufficient immunity to electromagnetic interference from the environment.
5. **What are the design methods for distinguishing between analog ground and digital ground in PCB design?**
There are several approaches to handling analog and digital grounds in PCB design:
– **Direct separation:** Connect the ground for the digital section as DGND and the ground for the analog section as AGND in the schematic, then divide the ground plane in the PCB into separate digital and analog sections with increased spacing between them.
– **Magnetic beads:** Use magnetic beads to connect the digital and analog grounds.
– **Capacitive coupling:** Connect the digital and analog grounds using capacitors, relying on the capacitor’s ability to block DC current.
– **Inductive coupling:** Use inductors to connect the digital and analog grounds, with inductance values typically ranging from microhenries (uH) to tens of microhenries.
– **Zero-ohm resistors:** A zero-ohm resistor can be placed between the digital and analog grounds.
In summary, capacitors can separate DC currents and create floating grounds. If a capacitor is not DC-coupled, it can lead to voltage differences and static charge buildup, potentially causing discomfort when touching the enclosure. When capacitors and magnetic beads are used in parallel, they can be redundant, as the magnetic beads pass DC, rendering the capacitors ineffective. If they are in series, the result can be less effective overall.
Inductors, while effective in some cases, tend to have large sizes and many stray parameters, leading to unstable performance and less precise control over distributed parameters. Inductance can also introduce notch effects and LC resonance, which can impact noise behavior.
The equivalent circuit of a magnetic bead acts like a band-rejection filter, suppressing noise at specific frequencies. However, if the noise frequency is unpredictable, choosing the right magnetic bead can be challenging, making them less ideal.
Zero-ohm resistors, by contrast, offer a narrow current path that effectively limits loop currents and suppresses noise across all frequencies, offering a more reliable solution than magnetic beads.
In conclusion, the key principle is that analog and digital grounds should be connected at a single point. It’s recommended to connect different types of grounds with 0-ohm resistors, use magnetic beads when introducing high-frequency components into the power supply, employ small capacitors for coupling high-frequency signal lines, and use inductors for high-power, low-frequency applications.
If you have any PCB manufacturing needs, please do not hesitate to contact me.Contact me
2. The ground plane should be larger than the power or signal layers to effectively reduce external radiation interference and shield the board from outside disturbances. In typical PCB design, shrinking the power layer by 1mm from the ground layer generally satisfies the 20H principle.
3. How to apply the 3W and 20H principles in PCB design?
The 3W principle is straightforward to implement in PCB design. Ensure that the center-to-center distance between traces is at least three times the trace width. For example, if the trace width is 6 mils, the center-to-center spacing should be set to 18 mils.
To meet the 3W principle in Allegro, set the line-to-line clearance rule to 12 mils, as the software calculates spacing based on the edge-to-edge distance.
4. As for the 20H principle, to implement it in PCB design, it is generally necessary to reduce the power layer by 1mm from the ground layer when dividing the plane layers.
Then, punch a shielding ground via on the 1mm shrink tape, with one 150mil via.
3. **What are the types of PCB signal lines and what are the differences?**
PCB signal lines are typically categorized into two types: microstrip lines and strip lines.
A microstrip line is a type of stripline that is placed on the surface layer (microstrip) and is attached to the top layer of the PCB. As illustrated below, the blue section represents the conductor, the green section is the insulating dielectric of the PCB, and the blue block on top is the microstrip line. Since one side of the microstrip line is exposed to air, it can radiate energy or be susceptible to interference from surrounding radiation, while the other side is in contact with the insulating dielectric of the PCB. Consequently, part of the electric field formed by the microstrip line is distributed in the air, and the other part is confined to the PCB’s insulating medium. The main advantage of microstrip lines is that they offer faster signal transmission speeds compared to striplines.
The stripline, or double stripline, is placed in the inner layers of the PCB and is embedded between two conductive layers. As shown in the diagram below, the blue part is the conductor, the green part is the insulating dielectric, and the stripline is embedded between two conductive planes. Since the stripline is sandwiched between two conductor layers, its electric field is confined within these two conductive planes, preventing energy radiation and shielding it from external interference. However, because the stripline is surrounded by dielectric material (with a dielectric constant greater than 1), the signal transmission speed in a stripline is slower than in a microstrip line.
4. **What is EMC?**
EMC stands for Electromagnetic Compatibility, referring to the ability of a device or system to operate properly in its electromagnetic environment without causing or suffering from harmful interference.
For sensors, electromagnetic compatibility refers to the sensor’s ability to function correctly in an electromagnetic environment while maintaining its inherent performance and meeting its specified functions. EMC for sensors includes two key requirements: First, the electromagnetic interference (EMI) generated by the sensor during normal operation should not exceed certain limits; second, the sensor should have sufficient immunity to electromagnetic interference from the environment.
5. **What are the design methods for distinguishing between analog ground and digital ground in PCB design?**
There are several approaches to handling analog and digital grounds in PCB design:
– **Direct separation:** Connect the ground for the digital section as DGND and the ground for the analog section as AGND in the schematic, then divide the ground plane in the PCB into separate digital and analog sections with increased spacing between them.
– **Magnetic beads:** Use magnetic beads to connect the digital and analog grounds.
– **Capacitive coupling:** Connect the digital and analog grounds using capacitors, relying on the capacitor’s ability to block DC current.
– **Inductive coupling:** Use inductors to connect the digital and analog grounds, with inductance values typically ranging from microhenries (uH) to tens of microhenries.
– **Zero-ohm resistors:** A zero-ohm resistor can be placed between the digital and analog grounds.
In summary, capacitors can separate DC currents and create floating grounds. If a capacitor is not DC-coupled, it can lead to voltage differences and static charge buildup, potentially causing discomfort when touching the enclosure. When capacitors and magnetic beads are used in parallel, they can be redundant, as the magnetic beads pass DC, rendering the capacitors ineffective. If they are in series, the result can be less effective overall.
Inductors, while effective in some cases, tend to have large sizes and many stray parameters, leading to unstable performance and less precise control over distributed parameters. Inductance can also introduce notch effects and LC resonance, which can impact noise behavior.
The equivalent circuit of a magnetic bead acts like a band-rejection filter, suppressing noise at specific frequencies. However, if the noise frequency is unpredictable, choosing the right magnetic bead can be challenging, making them less ideal.
Zero-ohm resistors, by contrast, offer a narrow current path that effectively limits loop currents and suppresses noise across all frequencies, offering a more reliable solution than magnetic beads.
In conclusion, the key principle is that analog and digital grounds should be connected at a single point. It’s recommended to connect different types of grounds with 0-ohm resistors, use magnetic beads when introducing high-frequency components into the power supply, employ small capacitors for coupling high-frequency signal lines, and use inductors for high-power, low-frequency applications.
If you have any PCB manufacturing needs, please do not hesitate to contact me.Contact me
