In any power supply design, the physical design of the PCB is the last link. The design method determines the electromagnetic interference and power supply stability. Let's analyze these links in detail:
First, from the schematic diagram to the PCB design process to establish component parameters -> input principle netlist -> design parameter settings -> manual layout -> manual wiring -> verification design -> review -> CAM output.
Second, the parameters set adjacent conductor spacing must be able to meet electrical safety requirements, and for ease of operation and production, the spacing should be as wide as possible. The minimum spacing should be at least suitable for the voltage to withstand. When the wiring density is low, the spacing of the signal lines can be appropriately increased. The signal lines with high and low levels should be as short as possible and the spacing should be increased. Under normal circumstances Set the trace spacing to 8 mil.
The distance from the edge of the pad to the edge of the board is greater than 1mm, which avoids pad defects during processing. When the traces connected to the pads are thinner, the connection between the pads and the traces is designed to be water droplets. This has the advantage that the pads are not easy to peel, but the traces are not easily disconnected from the pads.
Third, the component layout practice proves that even if the circuit schematic design is correct and the printed circuit board is not properly designed, it will adversely affect the reliability of the electronic equipment. For example, if the two thin parallel lines of the printed board are close together, the delay of the signal waveform will be formed, and the reflection noise will be formed at the end of the transmission line; the interference caused by the inconsistency of the power supply and the ground line will cause the product to be Performance is degraded, so when designing a printed circuit board, care should be taken to use the correct method.
4. The wiring switching power supply contains high-frequency signals. Any printed circuit on the PCB can function as an antenna. The length and width of the printed circuit will affect its impedance and inductance, thus affecting the frequency response. Even a trace through a DC signal can couple to an RF signal from an adjacent trace and cause a circuit problem (even radiating an interference signal again).
5. After the inspection wiring design is completed, it is necessary to carefully check whether the wiring design meets the rules set by the designer, and also to confirm whether the established rules meet the requirements of the printed board production process, and generally check the line and wire, wire and component welding. Whether the distance between the disk, the wire and the through hole, the component pad and the through hole, the through hole and the through hole is reasonable, and whether the production requirement is satisfied. Is the width of the power and ground wires appropriate? Is there a place in the PCB where the ground wire can be widened? Note: Some errors can be ignored. For example, some of the outlines of some Connectors are placed outside the board frame, and errors are detected when checking the spacing. In addition, each time the traces and vias are modified, the copper is re-copied once.
Sixth, review according to the "PCB checklist", the content includes design rules, layer definition, line width, spacing, pad, via settings, but also focus on reviewing the rationality of device layout, power, ground network routing, high speed Trace and shield of the clock network, placement and connection of decoupling capacitors, etc.
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