In the research of PCB reverse technology, the reverse schematic refers to the reverse derivation of PCB circuit diagram according to the PCB file diagram or directly according to the product, in order to explain the principle and working condition of the circuit board. Moreover, this circuit diagram is also used to analyze the functional characteristics of the product itself. However, in the forward design, the general product research and development should first carry out schematic design, and then proceed according to schematic design.
Whether it is used to analyze circuit board principles and product performance in reverse research, or reused as the basis and basis of PCB design in forward design, PCB schematics have a special role. So, according to the document diagram or the real thing, how to carry out the PCB schematic back push, back push process should pay attention to those details?
First, reasonable division of functional areas
In the reverse design of a good PCB schematic, reasonable division of functional areas can help engineers reduce some unnecessary trouble and improve the efficiency of drawing. Generally speaking, the components with the same function on a PCB board will be centrally arranged, and the functional division of the area can be a convenient and accurate basis for the backdrawing of the schematic.
However, the division of this functional area is not arbitrary. It requires engineers to have some knowledge of electronic circuits. First, the core component of a functional unit is found, and then other components of the same functional unit can be traced according to the wiring connection to form a functional partition. The formation of functional partition is the basis of schematic drawing. Also, during this process, don't forget to use the component numbers on the circuit board, which can help you partition functions faster.
Two, correctly distinguish lines, reasonable drawing wiring
For the distinction of ground wire, power cord and signal line, engineers also need to have relevant knowledge of power supply, circuit connection knowledge, PCB wiring knowledge and so on. The distinction of these lines can be analyzed from the connection of components, the width of copper foil and the characteristics of the electronic products themselves.
In wiring drawing, in order to avoid crossing and interspersing lines, a large number of ground symbols can be used for ground wires. Different lines of different colors can be used to ensure clear identification. Special marks can also be used for various components, and unit circuits can even be drawn separately and then combined.
Three, find the right reference piece
This reference piece can also be said to be the main component used in the schematic drawing at the beginning. After determining the reference piece, drawing according to the pins of these reference pieces can ensure the accuracy of the schematic diagram to a greater extent. For engineers, the determination of the reference is not a very complex thing, in general, you can choose to play a major role in the circuit components as the reference, they are generally larger, more pins, easy to draw, such as, transformer, transistor and so on, can be used as a suitable reference.
Four, master the basic framework, learn from similar schematic diagram
For some basic electronic circuit framework and schematic method, engineers need to master, not only to be able to draw some simple and classic basic cell circuit composition form directly, but also to form the overall framework of electronic circuit.
On the other hand, it should not be ignored that the schematic diagram of the same type of electronic products has certain similarities, so engineers can draw on the schematic diagram of the same kind of circuit according to the accumulation of experience to carry out the backdrawing of the schematic diagram of the new product.
Five, check and optimization
After the schematic drawing is completed, the reverse design of PCB schematic diagram can be concluded only after testing and checking. The nominal values of components sensitive to PCB distribution parameters need to be checked and optimized. The schematic diagram is compared, analyzed and checked according to the PCB file diagram to ensure that the schematic diagram is completely consistent with the file diagram.
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