1. The design of PCB--- brief introduction and design steps

1.The design of PCB
Juvtmall ( a company supply PCB PrototypingPCBA service and sell kinds of components, modules and so on) 

In PCB design, the layout of the components and the wiring of the circuit are the two key links.

Layout, means the circuit device in the printed circuit board wiring area.
Whether the layout is reasonable not only affects the wiring work at the back, but also has an important effect on the performance of the whole circuit board.
After guaranteeing the circuit function and performance index, to satisfy the requirement of process, testing and maintenance aspects, components should be uniform, neat and compact  on the PCB, as far as possible to reduce and shorten the lead and the connection between components, in order to get symmetrical packing density.

The position of each functional circuit unit is arranged according to the circuit process, the input and output signal, the high level and the low level part are uncrossed as far as possible, and the signal transmission route is the shortest.

The position of the components shall be grouped according to the power supply voltage, digital and analog circuit, speed and current size, so as to avoid interference.

When both the digital circuit and analog circuit are installed on the circuit board, the ground electrode and the power supply system of the two circuits are completely separated, and the digital circuit and analog circuit are arranged in different layers. When the circuit boards need to be arranged fast, medium-speed and low-speed logic circuit, they should be placed close to the connector. While low speed logic and memory should be placed away from the connector. In this way, the total impedance coupling, radiation and cross interference are reduced.
The clock circuit and the high frequency circuit are the main source of harassment, must be arranged separately to away from the sensitive circuit.

Considering the thermomagnetic : the heating element and the thermal sensor are as far away as possible, considering the influence of electromagnetic compatibility.

2. PCB design steps
The design of circuit schematic diagram is the basis of the whole circuit design, and its design is directly determined by the effect of PCB design. Generally speaking, the design of circuit schematic diagram is as follows:

Step 1: start the ProtelDXP schematic editor
Step 2: set the size and layout of the schematic diagram
Step 3: remove the required elements from the library and place them in the working plane
Step 4: connect the components according to the design
Step 5: adjust the components after wiring
Step 6: save the schematic diagram document
Step 7: print out the output drawing



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5. The design of PCB--design considerations and assembly rules