High Frequency Circuit Board Wiring
1. The shorter the lead between the pins of a high-frequency circuit board device, the better. The radiation intensity of the signal is proportional to the trace length of the signal line. The longer the high-frequency signal lead, the more likely it is to couple with nearby components. Therefore, signals such as clock, crystal oscillator, DDR data, LVDS lines, USB lines, HDMI lines, and other high-frequency signal lines should be as short as possible.
2. The fewer the number of layer transitions between the pins of a high-frequency circuit device, the better. This means that the fewer vias used in the component connection process, the better. Each via introduces about 0.5 pF of distributed capacitance, and reducing the number of vias can significantly increase signal speed and reduce data errors.
3. Pay attention to the “crosstalk” introduced by parallel signal lines that are close to each other. High-frequency circuit wiring should consider the “crosstalk” caused by close parallel routing of signal lines. Crosstalk refers to the unintended coupling between signal lines that are not directly connected. High-frequency signals are transmitted as electromagnetic waves along the transmission line, making the signal line act like an antenna. The electromagnetic field energy emitted around the transmission line can cause undesirable noise signals due to mutual coupling of the fields between signals. The PCB layer parameters, signal line spacing, electrical characteristics of the driving and receiving ends, and signal line termination methods all affect crosstalk. To reduce crosstalk in high-frequency signals, follow these guidelines:
– If space permits, insert a ground wire or ground plane between two wires with significant crosstalk to provide isolation and reduce interference.
– If parallel routing is unavoidable, place a large ground area opposite the parallel signal line to significantly reduce interference.
– Increase spacing between adjacent signal lines if space allows, minimize the parallel length of the signal lines, and align the clock line perpendicular to the key signal line rather than parallel.
– When parallel routing in the same layer is unavoidable, ensure that the wiring directions in adjacent layers are perpendicular to each other.
– In digital circuits, where clock signals have fast edge changes and high external crosstalk, surround the clock line with a ground line and add more ground vias to reduce distributed capacitance and crosstalk.
– For high-frequency signal clocks, use low-voltage differential clock signals and maintain proper grounding of the package to ensure signal integrity.
– Unused input terminals should be grounded or connected to the power supply, rather than left floating. Floating lines can act as antennas, and grounding can help suppress emissions. This practice has been shown to effectively eliminate crosstalk in some cases.
4. Add a high-frequency decoupling capacitor to the power supply pin of each integrated circuit block. Adding a high-frequency decoupling capacitor near the power supply pin of each integrated circuit block can effectively suppress high-frequency harmonic interference on the power supply line.
PCB Design and Manufacturing Package
1. Speed up and improve PCB wiring. Traditional PCB wiring is constrained by fixed wire coordinates and limited angles. Removing these constraints can significantly enhance wiring quality. This article discusses the benefits of arbitrary-angle wiring, flexible wiring, and presents a new algorithm for constructing Steiner trees through practical examples.
2. Key considerations for PCB design from the perspective of soldering. Despite the advancement of placement machines that can replace manual soldering, many factors still affect soldering quality. This article highlights crucial aspects to consider when designing PCBs with patch soldering in mind. Failure to adhere to these considerations may result in poor soldering quality, false solder joints, or even damage during PCB repair.
3. Wiring skills and essentials for PCB design. Wiring is one of the most intricate and restrictive aspects of PCB design. This section covers effective wiring techniques and essential practices.
PCB Simulation and DDR3 Memory Design
Analyze the main factors affecting signal integrity in DDR3 timing, and use these insights to enhance and optimize the design.
1. The shorter the lead between the pins of a high-frequency circuit board device, the better. The radiation intensity of the signal is proportional to the trace length of the signal line. The longer the high-frequency signal lead, the more likely it is to couple with nearby components. Therefore, signals such as clock, crystal oscillator, DDR data, LVDS lines, USB lines, HDMI lines, and other high-frequency signal lines should be as short as possible.
2. The fewer the number of layer transitions between the pins of a high-frequency circuit device, the better. This means that the fewer vias used in the component connection process, the better. Each via introduces about 0.5 pF of distributed capacitance, and reducing the number of vias can significantly increase signal speed and reduce data errors.
3. Pay attention to the “crosstalk” introduced by parallel signal lines that are close to each other. High-frequency circuit wiring should consider the “crosstalk” caused by close parallel routing of signal lines. Crosstalk refers to the unintended coupling between signal lines that are not directly connected. High-frequency signals are transmitted as electromagnetic waves along the transmission line, making the signal line act like an antenna. The electromagnetic field energy emitted around the transmission line can cause undesirable noise signals due to mutual coupling of the fields between signals. The PCB layer parameters, signal line spacing, electrical characteristics of the driving and receiving ends, and signal line termination methods all affect crosstalk. To reduce crosstalk in high-frequency signals, follow these guidelines:
– If space permits, insert a ground wire or ground plane between two wires with significant crosstalk to provide isolation and reduce interference.
– If parallel routing is unavoidable, place a large ground area opposite the parallel signal line to significantly reduce interference.
– Increase spacing between adjacent signal lines if space allows, minimize the parallel length of the signal lines, and align the clock line perpendicular to the key signal line rather than parallel.
– When parallel routing in the same layer is unavoidable, ensure that the wiring directions in adjacent layers are perpendicular to each other.
– In digital circuits, where clock signals have fast edge changes and high external crosstalk, surround the clock line with a ground line and add more ground vias to reduce distributed capacitance and crosstalk.
– For high-frequency signal clocks, use low-voltage differential clock signals and maintain proper grounding of the package to ensure signal integrity.
– Unused input terminals should be grounded or connected to the power supply, rather than left floating. Floating lines can act as antennas, and grounding can help suppress emissions. This practice has been shown to effectively eliminate crosstalk in some cases.
4. Add a high-frequency decoupling capacitor to the power supply pin of each integrated circuit block. Adding a high-frequency decoupling capacitor near the power supply pin of each integrated circuit block can effectively suppress high-frequency harmonic interference on the power supply line.
PCB Design and Manufacturing Package
1. Speed up and improve PCB wiring. Traditional PCB wiring is constrained by fixed wire coordinates and limited angles. Removing these constraints can significantly enhance wiring quality. This article discusses the benefits of arbitrary-angle wiring, flexible wiring, and presents a new algorithm for constructing Steiner trees through practical examples.
2. Key considerations for PCB design from the perspective of soldering. Despite the advancement of placement machines that can replace manual soldering, many factors still affect soldering quality. This article highlights crucial aspects to consider when designing PCBs with patch soldering in mind. Failure to adhere to these considerations may result in poor soldering quality, false solder joints, or even damage during PCB repair.
3. Wiring skills and essentials for PCB design. Wiring is one of the most intricate and restrictive aspects of PCB design. This section covers effective wiring techniques and essential practices.
PCB Simulation and DDR3 Memory Design
Analyze the main factors affecting signal integrity in DDR3 timing, and use these insights to enhance and optimize the design.
