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20 mil RO4003C PCB
20 mil RO4003C PCB
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Key Points of High Frequency Circuit Board Layout

  • March 23. 2022

The rapid development of science and technology determines that all enterprises need to improve, and PCB depends on science and technology, so it is natural not to lag behind. Therefore, the layout of high-frequency PCB has become the key point that we need to discuss when designing PCB high-frequency board. Today, we sorted out the key points you need to pay attention to in the layout of high-frequency PCB. Let's have a look!


(1) High-frequency circuits tend to have high integration and high-density wiring. The use of multilayer is both necessary for wiring and an effective means to reduce interference.


(2) The less lead bending between pins of high-speed circuit devices, the better. The lead wire for hf circuit wiring is preferably solid wire, which needs to be wound, and can be folded in 45° or arc. In order to meet this requirement, external transmission and mutual coupling of high frequency signals can be reduced.


(3) The shorter the lead between the pins of the high-frequency circuit device, the better.


(4) The less the alternating of wiring layers between pins of high-frequency circuit devices, the better. "Minimizing interlayer crossings" refers to the use of as few vias as possible during component connections. It is estimated that a single vias can deliver approximately 0.5 pF of distributed capacitance. Reduce the number of through-holes. Can greatly improve the speed.


(5) The wiring of high frequency circuit should pay attention to the "cross interference" introduced by parallel lines of signal lines. If parallel distribution cannot be avoided, a large area of "grounding" can be placed on the back of parallel signal lines to greatly reduce interference. Parallel cabling in the same floor is almost inevitable, but in two adjacent floors, the direction of cabling must be perpendicular to each other.


(6) grounding measures surrounding particularly important signal lines or local units, that is, drawing the external contour of the selected object. With this feature, so-called "packet" processing can be performed automatically on selected important signal lines. Of course, using this functionality for local processing of components such as clocks is also very beneficial for high-speed systems. Sichuan Shenya electronics co., Ltd. is a high-tech enterprise specializing in PCB rapid proofing, production and sales. Independent research and development of PCB online ordering system professional production of multi-layer board, difficult board, HDI high-frequency board, mixed plate! Rogers mix! Soft and hard bonding board! SMD patch! BOM with single! One-stop service


(7) All kinds of signal wiring can not form a loop, and the grounding line can not form a current loop.


(8) A high frequency decoupling capacitor shall be placed near each IC block.


(9) When connecting analog and digital ground wires to common ground wires, high-frequency turbulent links shall be used. In the actual assembly of high-frequency turbulence chains, high-frequency ferrite beads passing through the center hole are often used, and are usually not represented in the circuit schematic diagram, and the resulting netlist does not include such components, so the wiring will ignore their existence. In response to this reality, it can be used as an inductor in the schematic, and the component package can be defined separately in the PCB component library and manually moved to a suitable position near the convergence point of the common ground wire prior to wiring.


(10) Analog and digital circuits should be arranged separately. After independent wiring, the power supply and ground wire should be connected at one point to avoid mutual interference.


(11) Before connecting the program memory and data memory outside the DSP chip to the power supply, filter capacitor should be added and placed as close as possible to the chip power pin to filter out the power supply noise. In addition, shielding around DSP and off-chip program memory and data memory is recommended to reduce external interference.


(12) The off-chip program memory and data memory should be placed as close to the DSP chip as possible. At the same time, the layout should be reasonable so that the length of data lines and address lines is basically the same, especially when there are multiple memories in the system, the clock line of each memory should be considered. Clock input distances are equal, or separate programmable clock driver chips can be added. For THE DSP system, select the external memory with the same access speed as THE DSP; otherwise, the high-speed processing capability of DSP cannot be fully utilized. DSP instruction cycle is nanosecond, so the most common problem in DSP hardware system is high frequency interference. Therefore, when making the PRINTED circuit board (PCB) of DSP hardware system, special attention should be paid to address line and data line. The connection of signal cables should be correct and reasonable. When connecting cables, make the high-frequency cables short and thick, and keep them away from easily disturbed signal cables, such as analog signal cables. When the circuit around the DSP is more complex, it is recommended to combine the DSP with its clock circuit, reset circuit, off-chip program memory and data memory into a minimal system to reduce interference.


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