PCB board layout design!

We know that some special components have special requirements for layout and wiring. For example, analog signal amplifiers require stable power supply and small ripple. The analog small signal part should be kept away from the power device as much as possible. A shielding cover is specially added to the small-signal amplifying part to shield the stray electromagnetic interference. Special consideration must be given to the heat dissipation problem during the layout. If natural heat dissipation is used, the chip must be placed in a place where the air circulation is relatively smooth, and the heat dissipated cannot have a great impact on other chips. If the board is equipped with speakers or other high-power devices, it may cause serious pollution to the power supply, which should also be paid enough attention.

In the PCB factory, one of the first factors to be considered in the layout of automotive circuit board components is electrical performance. The components that are closely related to the wiring should be placed together as much as possible, especially for some high-speed lines, the layout should be as short as possible. , power signal and small signal devices should be separated. On the premise of satisfying the circuit performance, it is also necessary to consider that the components are placed neatly and beautifully, which is convenient for testing. The mechanical size of the board and the location of the socket also need to be carefully considered. Grounding and propagation delay times on interconnects in high-speed systems are also the first considerations in system design. The transmission time on the signal line has a great influence on the overall system speed, especially for high-speed ECL circuits, which is the abbreviation of Emitter Couple Logic integrated circuits. Different from TTL circuits, the biggest feature of ECL circuits is its basic gate. The circuit works in a non-saturated state. Therefore, the biggest advantage of ECL circuits is that they have a relatively high speed. The average delay time of this circuit can reach several nanoseconds or even sub-nanoseconds. This makes ECL integrated circuits in high-speed and ultra-high-speed digital. It plays an unmatched role in the system) circuit, although the speed of the integrated circuit itself is very high, but the delay time increases due to the use of ordinary interconnect lines (about 2ns delay per 30cm line length) on the backplane. It can greatly reduce the speed of the system (like a shift register). It is better to put the synchronous working components such as the synchronous counter on the same board, because the transmission delay time of the clock signals to different boards is not equal, which may cause the shift. If the bit register cannot be placed on one board, the length of the clock lines from the common clock source to each plug-in board must be equal in places where synchronization is critical.

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