One of high-speed PCB design guidelines
The first article PCB wiring
In PCB design, cabling is an important step of finished product design, can say the preparation work ahead for it and do, in the whole PCB, the design process specifies in wiring the highest, fine, greatest workload skills. PCB wiring a single-sided wiring, double-sided wiring and multi-layer wiring. Wiring way also has two kinds: automatic wiring and interactive wiring, in automatic wiring in advance, can use an interactive before to demand is strict line for wiring, input and output should be avoided the touchline parallel, lest produce reflection adjacent interference. When necessary, two adjacent add landlines isolation layer of wiring to mutually perpendicular, parallel easy to produce the parasitic coupling.
Automatic wiring cloth tong rate, depends on good layout and wiring rules can pre-set wiring bends, including frequency, the number of conduction hole, stepping number, etc. General to explore type cloth at warp, quickly take short line connectivity, then first wiring, labyrinth of attachment to cloth for global wiring path optimization, it may, according to needs to disconnect the line already cloth. And try again to improve overall effect, wiring.
The PCB design for the current density already feel transfixion hole not too orientation, it wasted a lot of valuable wiring channel, to solve this contradiction, the emergence of a blind holes and buried via technology, it not only completed the role of conduction hole, also province out many wiring channel make wiring process finished more convenient, more smooth, more perfect, PCB design process is a complicated and simple process, must want to master it well, still need to general electronic engineering design personnel to from already experience, to get one of the true.
1 power supply, ground treatment
Even in the wiring in the whole PCB finish all very good, but due to a power supply, landlines consideration not attentive and cause interference, can make the product performance drop, sometimes even affect product success rate. So for electricity, ground wiring should be taken seriously, the electricity, landlines generated noise to a minimum, in order to guarantee the quality of its products.
For each engaged in electronic product design engineers with both understand ground between noise generated power to reduce, presently only reason with the expression of suppression of noise:
(1), known in power supply, ground is between plus decoupling capacitor.
(2), try to widen power supply, landlines width, it is better than the power cord ground, their relationship is wide > > : ground power signal, usually due to the wide for: 0.2 ~ 0.3 mm, the most by fine width can reach 0.05 ~ 0.07 mm, the power cord for 1.2 ~ 2.5 mm
The PCB available for digital circuit composed a wide ground wire loop, namely constitute a mechanical to use (analog circuit to can"t use)
(3), have a large copper layer on the ground in the PCB with, was not the place to use and connect with as ground. Or make it produce multilayer prototypes, power, ground floor. Each occupy
2 digital circuit and analog circuit in ground processing
Now there are many PCB is no longer a single functional circuits (digital or analog circuit), but by analog and digital circuitry consists of a mix. So in wiring will need to consider their mutual interference problems, especially the noise on the ground.
Digital circuits, analog circuit is the frequency of the high sensitivity to signal speaking, strong, high frequency signal as far sensitive analog circuits to landlines speaking, device that only one of those trick PCB outside, so must node number internal treatment PCB, mold, and the problems of digital and in board internal simulated as is actually separate them between each other is not connected with the outside world, just in PCB connect outlet (such as plug, etc.). With analog to digital has a little short sub, please note that only a connection. It can also be in the PCB, the tenant by system design to decide.
3 in the electrical signal cloth (ground) layer
In multilayer PCB wiring, due to finish in the signal layer no cloth, then left are numbered line add layer can cause waste would also give the workload increased production must, costs are a corresponding increase in, to solve this contradiction, may consider the electricity (ground) layer on the wiring. First should consider use power layer and secondly strata. Because the best is to retain the integrity of the strata.