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How To Deal With PCB Sensitive Circuits? What Are The Interference Elements?


Published by: Keyou October 22,2019

1. How to deal with PCB sensitive circuits
     (1) Power cord
     According to the current of the printed circuit board, try to increase the width of the power line and reduce the loop resistance. In particular, it is necessary to make the power supply direction in the power line and the ground line opposite to the data and signal transmission direction, that is, the power supply mode that is advanced from the final stage to the front stage, which helps to enhance the anti-noise capability.

(2) Ground wire
    The principle of design is to separate the digital ground from the simulated ground. If there are both logic and linear circuits on the board, they should be separated as much as possible. The ground of the low-frequency circuit should be grounded in parallel with a single point. If the actual wiring is difficult, it can be partially connected and then grounded in parallel. The high-frequency circuit should adopt multi-point series grounding, the ground wire should be short and rented, and the grid-like large-area foil should be used as much as possible around the high-frequency components. The ground wire should be as thick as possible. If the grounding wire uses a very thin line, the ground potential changes with the change of the current, which reduces the noise immunity. Therefore, the ground wire should be thickened so that it can pass three times the allowable current on the printed board. If possible, the grounding wire should be 2~3mm or more. The ground wire forms a closed loop. In a printed circuit board composed only of digital circuits, the grounding circuit is mostly formed into a loop, which can improve the anti-noise capability.

    2. What interference elements are in the PCB?
    Source refers to the component, device or signal that causes interference. It is described in mathematical language as follows: du/dt, where di/dt is large, is the source of interference. Such as: lightning, relays, thyristors, motors, high-frequency clocks, etc. may become sources of interference. A propagation path is a path or medium that interferes with the propagation from an interferer to a sensitive device. A typical interference propagation path is the conduction through the wires and the radiation from the space. Sensitive components are objects that are easily disturbed. Such as: A / D, D / A converter, microcontroller, digital IC, weak signal amplifier.
    3, can be divided into radiation and conducted interference
    Radiated interference is the interference source that uses space as a medium to interfere its signal with another electrical network. Conducted interference is the use of a conductive medium as a medium to interfere with signals on one electrical network to another. In high-speed system design, integrated circuit pins, high-frequency signal lines and various types of plugs are common sources of radiated interference in PCB design. The electromagnetic waves they emit are electromagnetic interference (EMI), which affects itself and other systems. normal work. Baineng Network is a subsidiary of Qinji Group. It is a leading electronic industry service platform in China. It provides components, sensor procurement, PCB customization, BOM distribution, material selection and other electronic industry supply chain solutions. The overall needs of small and medium-sized customers in the industry.
    4, how to deal with sensitive components in the PCB
    When components are placed, they must be compatible with production and maintainability. The polarity of the capacitor should be the same. The heating components and sensitive components should be placed at a distance. Moisture sensitive components tend to be packaged in tape-and-reel systems, each with a large number of components. When compared to the lead components in the IC tray, the key issue is that the exposure to moisture is longer. The exposure time must be increased to dry storage time during setup and processing.