The importance of electronic product stability We already have a deep understanding, we certainly do not want to buy a daily need to correct the smart bracelet, do not want to buy an easy to crash electronic products. Once this happens in the electronic products we buy, then the fate of this electronic product may be to the end of the day, the product in your hands I am afraid to eat ash in the drawer corner or become lost in the hands of the child's toys.

Electronic products will produce abnormalities affected by many factors, such as ESD, EMI or the principle of design flaws and so on. So how to design a stable performance of electronic products, need to pay attention to several aspects.

First, eliminate the design flaws
This part is very important, especially in the external interface circuit requires low power design, it should be more attention, such as a button, usually in the design, usually designed to pull up to VDD, but in low power design, It needs to be connected to GND, when there is action when the pull to VDD.
In addition to the design features for the product design, but also help the choice of components. Such as packaging, power consumption, work environment, etc. are needed to consider.

Second, the rational layout
This part is a technology or an art problem. Reasonable layout requires reasonable arrangements between the system equipment, the connection between the various units, location and how to track. Need to pay attention to the place is high-speed vulgar separation, analog digital separation, interference source away from the core components. Pay attention to high-frequency connection as short as possible, grounding resistance as small as possible, I believe this is for electronic engineers, is a roll of endless books. This reminds me of a word: a good performance PCB board is a good product, the layout is a work of art.

Third, do a good job shielding
Usually designed vulgar PCB does not need to do any shielding system can also work properly. But you open to see the phone, handheld or other communications equipment, found that the key RF circuit is often hidden in the Faraday cage, this is a way to shield.

Shielding as an effective way to suppress radiation interference, often used in the worst serious disaster areas, but not as long as the use of shielding can be a good solution to EMI problems, accompanied by grounding problems, and only shield and ground can be used to play a shield The greatest effect. If there is no grounding, then the electric cage or become a collection of energy flat antenna and launch a more powerful energy EMI.

Shielded with electrical shielding, magnetic shielding and electromagnetic shielding. Different shielding techniques use different shielding design methods:

Electrical shielding is usually selected copper and aluminum alloy as a shielding material, in the high-frequency shielding need to shield the surface of the mask silver. For its shape, the general selection of box-like to get a good shielding performance. Do not open the hole on the shield, to avoid electric field energy leakage. If the hole has to be opened for some reason (heat dissipation), the number of openings is as small as possible and the opening area is as small as possible.

Learn the electromagnetic field courses all know that in the low-frequency magnetic field, the eddy current shielding effect is very small, usually require high permeability materials for shielding. The thicker the shield, the higher the magnetic permeability, the better the magnetic shielding effect. Magnetic shielding using steel plate to do shield, if necessary, can be double shield.

For the electromagnetic shielding and electrical shielding can be used the same method, and according to the actual situation to select the appropriate conductive pads, comb reed, shield display window and other methods to achieve electromagnetic seal.

Fourth, do the isolation

For the normal IO interface, if you need to detect the external voltage or switch status, can be directly connected, but, in order to prevent over-current or overvoltage need to protect the IO port, then I can use IO port isolation method, transistor and optocoupler The use of a good way, in addition to transformer isolation, component isolation and other methods.

Fifth, good grounding

On the grounding technology, see: electronic design have to say that the grounding technology

The above content is in the design circuit and debugging circuit experience in the summary, with the development of technology believe that there are more ways for PCB design, which also records the growth of each electronic engineer.