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Basics Of PCB Design Must Be Mastered
Oct 16, 2017

Basics of PCB design must be mastered

1. If the designed circuit system contains FPGA devices, the pin assignments must be verified using the Quartus II software before drawing the schematic. (Some special pins in the FPGA can not be used as normal IO).

2, 4-layer board from top to bottom are: signal plane layer, ground, power, signal plane layer Power supply, signal plane layer. 6 layers above the board (the advantage is: anti-interference radiation), give priority to select the inner layer of the line, can not get away from the choice of plane layer, to prohibit the ground from the ground or power line (reason: will split the power layer, resulting in parasitic effects).

3, multi-power system wiring: FPGA + DSP system to do 6-layer board, generally at least 3.3V + 1.2V + 1.8V +5 V.

3.3V is generally the main power supply, directly shop the power layer, through the hole is easy to spread through the global power network;

5V may be the power input, only in a small area of copper shop. And as thick as possible

1.2V and 1.8V are core power (if the direct use of the line will face BGA devices in the face of great difficulties), the layout as much as possible to 1.2V and 1.8V separately, and 1.2V or 1.8V connected The components are laid out in a compact area, using copper foil.

In short, because the power network throughout the PCB, if the use of alignment will be very complicated and will be very far away, the use of copper method is a good choice!

4, between the adjacent lines using cross-way: both parallel wires can reduce the electromagnetic interference between, and easy to track.

5, the analog number to be isolated, how to isolate the layout of the device will be used for analog signal and digital signal devices separately, and then from the middle of the AD chip across the board!

6, PCB design software based on PCB design can also be seen as a software development process, software engineering, the most focus on "iterative development" thinking, reduce the probability of PCB errors.

(1) schematic inspection, with particular attention to the device's power and ground (power and ground is the system of blood, can not have the slightest negligence);

(2) PCB packaging rendering (to confirm the schematic diagram of the pin is wrong);

(3) PCB package size confirmed one by one, add validation tags, add to the design package library;

(4) into the netlist, while adjusting the edge of the layout of the signal sequence (after the layout can not use OrCAD's automatic component function);

(5) manual wiring (side cloth edge check the power to the network, said earlier: the power network using copper way, so less with the alignment);

In short, the guiding ideology in PCB design is to draw the layout of the package layout and routing feedback (from the correctness of the signal connection, the convenience of signal routing considerations).

7, crystal from the chip as close as possible, and the crystal as much as possible without alignment, paving the network copper. The clocks used for multiple use are routed using the tree clock tree.

8, the arrangement of the signal on the connector on the difficulty of the greater degree of wiring, so the edge of the wiring side of the adjustment of the signal on the schematic (but do not re-symbolize the components).

9, multi-board connector design:

(1) the use of cable connection: up and down the same interface;

(2) straight socket: upper and lower interface mirror symmetry, as shown below:

10, the module connection signal design:

(1) If the two modules placed on the same side of the PCB, the discipline number is large then large (mirror connection signal);

(2) If the two modules on the PCB different surface, the discipline number is small and then large.

Doing so can place the signal as if it were on the right as above. Of course, the above method is not a rule, I always say, everything on demand and change (this can only comprehend himself), but in many cases in this way design is very useful.