pcb layout principle

- Jul 07, 2017-

power, ground handling

    Even if the wiring in the entire PCB board is done very well, but due to power, ground considerations are not thoughtful interference caused by the performance of the product will decline, and sometimes even affect the success rate of the product. So the power supply, ground wiring to be taken seriously, the power, ground noise generated by the interference to a minimum, to ensure product quality.

    For each engineer engaged in the design of electronic products are aware of the noise between the line and the power of the reasons, only to reduce the suppression of noise for the expression:

    It is well known that a decoupling capacitor is added between the power supply and the ground.

    As far as possible to widen the power, ground width, preferably ground than the power line width, their relationship is: ground> power line> signal line, usually signal line width: 0.2 ~ 0.3mm, the most fine width 0.05 ~ 0.07mm, the power line is 1.2 ~ 2.5mm.

    The PCB of the digital circuit can use a wide wire to form a loop, which constitutes a ground to use (analog circuit can not be used).

    With a large area of copper for the ground, in the printed circuit board on the place not used to connect with the ground as a ground. Or made of multi-layer board, power, ground each occupied a layer.

    2, digital circuit and analog circuit common ground processing

    Now there are many PCB is no longer a single functional circuit (digital or analog circuit), but by the digital circuit and analog circuit mix. So when wiring need to consider the interference between them, especially on the ground noise interference.

    Digital circuit frequency is high, the sensitivity of the analog circuit is strong, the signal line, the high-frequency signal line as far as possible away from the sensitive analog circuit devices, the ground, the whole PCB on the outside world only one node, so Must be handled within the PCB number, the problem of the common ground, and in the board of digital and analog ground is actually separated from each other are not connected, but in the PCB and the external interface (such as plugs, etc.). Digital and analog to a little short, please note that there is only one connection point. There are not on the PCB, which is determined by the system design.

    3, the signal line in the electrical (ground) layer

    In the multi-layer printed circuit board wiring, because the signal line layer is not finished cloth line left is not much, and then add more layers will cause waste will also increase the production of a certain amount of work, the cost has increased accordingly To solve this contradiction, you can consider wiring in the electrical (ground) layer. First consider the power layer, followed by the formation. Because it is best to preserve the integrity of the formation.

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