How to deal with PCB sensitive circuit
(1) the power cord
According to the size of printed circuit board current, try to make the power line width thicker to reduce the loop resistance. In particular, attention should be paid to the direction of power supply in the power line and ground wire, contrary to the direction of data and signal transmission, namely, the way of power supply from the final stage to the front stage, which is helpful to enhance the anti-noise ability.
(2) the ground
The design principle is) to separate the digital from the analog. If there are both logical and linear circuits on the circuit board, keep them as separate as possible. The ground of low frequency circuit should use single point parallel grounding as far as possible. When the actual wiring is difficult, it can be connected in series partly and then connected in parallel. The high frequency circuit should adopt multi-point serial grounding, the ground wire should be short and rented, and the large area of raster ground foil should be used around the high frequency components as far as possible.
Grounding wires should be as thick as possible. If the grounding wire is very flexible, the grounding potential will change with the change of current, which will reduce the anti-noise performance. The grounding wire should therefore be thickened so that it passes through three times the allowable current on the printed board. If possible, the grounding wire should be above 2 ~ 3mm. The ground wire forms a closed loop. For the printed board composed of digital circuit, the ground circuit is arranged into a group loop, which can improve the anti-noise ability.
What interference elements are in THE PCB
Source refers to the components, equipment or signals that produce interference, described in mathematical language as follows: du /dt, di/dt big place is the source of interference. Such as: lightning, relays, silicon controlled, motor, high frequency clock can be a source of interference. Propagation path refers to a path or medium through which interference propagates from an interference source to a sensitive device. Typical interference propagation paths are conduction through the wire and radiation in space. Sensitive components refer to objects easily interfered with. Such as: A/D, D/A converter, single chip microcomputer, digital IC, weak signal amplifier.
Can be divided into radiation and conduction of interference
Radiation interference is an interference source that uses space as a medium to interfere with its signal to another electrical network. Conductive interference, on the other hand, is the use of a conductive medium as a medium to interfere with signals from one electrical network to another.
In high-speed system design, integrated circuit pins, high-frequency signal lines and various connectors are common sources of radiation interference in PCB board design. The electromagnetic wave they emit is electromagnetic interference (EMI), which will affect the normal operation of themselves and other systems.
How to deal with sensitive components in PCB
Components should be placed in accordance with the production and maintenance convenience.
Capacitance should be of the same polarity. Heat components and sensitive components should be placed apart. Moisture-sensitive components tend to be packaged in a tape-and-reel system, with a large number of components per reel. When compared to pin components in IC trays, the key issue is longer exposure to moisture. During setup and treatment, exposure time must be increased to dry storage time.
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