In the research of PCB reverse technology, the backstepping schematic diagram refers to the PCB circuit diagram, which is based on the PCB file diagram or is directly drawn from the product physical objects, so as to illustrate the circuit board principle and work situation. And the circuit diagram is also used to analyze the functional features of the product itself. In the forward design, the R & D of the general product should be designed first, and then the PCB is designed according to the schematic diagram.
Whether it is used to analyze PCB principle and product characteristics in reverse research, or to be used as the basis and basis of PCB design in forward design, PCB schemas play a special role. So, according to the file or the object, how to do the backstepping of the PCB schematic, the backstepping process should pay attention to those details?
1. A rational division of functional areas
In the reverse design of a good PCB circuit board, reasonable partitioning of function area can help engineers reduce unnecessary troubles and improve rendering efficiency. Generally speaking, the components of the same function on a PCB board will be arranged in a centralized way, and the functional division area can be easily and accurately based on the backstepping schematic.
However, the division of this functional area is not arbitrary. It requires an engineer to have a certain knowledge of electronic circuit related knowledge. First of all, find out the core element of one of the functional units, then according to the line connecting the other components can be found with a functional unit will take, form a partition function. The formation of functional partitions is the basis of schematic drawing. In addition, in this process, do not forget to skillfully use the serial number of components on the circuit board, which can help you to perform functional zoning faster.
Two. Correctly distinguish the line and draw the wiring properly
The distinction between ground line, power line and signal line also requires engineers to have relevant power knowledge, circuit connection knowledge, PCB wiring knowledge and so on. The distinction of these lines can be analyzed from the connection of the components, the width of the line copper foil and the characteristics of the electronic product itself.
In order to avoid wiring drawing, line crossing and thrust, and can be used in large amounts of symbol grounding wire, different lines of various lines can use different colors to ensure clear, components can also use special signs of all kinds, can even separate unit circuit drawing, and finally combined.
Three. Look for a pair of benchmarks
This benchmark can also be used as the main component of the drawing at the beginning of the schematic drawing. After determining the reference part, drawing according to the pins of these reference parts can guarantee the accuracy of the schematic diagram to a greater extent.
For engineers, the benchmark is not very complicated, in general, can choose to play a major role in the circuit components as a benchmark, they are generally larger and more convenient for the pin, drawing, such as integrated circuit, transformer, transistors and so on, can be used as a suitable benchmark.
Four. Master the basic framework and draw lessons from similar principles
For some basic electronic circuits, the engineers should master the frame structure and schematic drawing method, not only to draw directly the basic components of some simple and classical unit circuits, but also to form the overall framework of electronic circuits.
On the other hand, do not neglect that the same type of electronic products have some similarities in schematic diagram. Engineers can learn from similar circuit diagrams to make new product schematic backstepping based on experience accumulation.
Five, verification and optimization
After the completion of the schematic drawing, it is necessary to pass the test and check link to say that the reverse design of the PCB schematic is finished. The nominal value of components sensitive to PCB distribution needs to be checked and optimized. According to the PCB file diagram, the schematic diagram is compared and checked to ensure that the schematic diagram is identical with the file map.