The creation background of SMD LAN transformer

With the popularization and development of wired LAN, establishing a wired LAN in one unit can realize mutual communication between leaders and various departments, and work efficiency can be greatly improved.

In a wired LAN, communication between servers, routers, hubs, computers, etc. is achieved by connecting their cables and twisted pairs, but because the connecting cables and twisted pairs are long. The longest one can reach one hundred meters, directly connecting the electronic devices in the two parts will bring a lot of problems.

First of all, the ground potential of the two places is different, a very low frequency of the slowly varying voltage will be formed at both ends of the connecting line, and the ramping voltage will be directly applied to the integrated circuit chip of the internal network card of the device in the two places, resulting in an integrated circuit chip. Burned out.

Secondly, the long line of nearly 100 meters is equivalent to a long antenna. The external electromagnetic interference (including lightning interference with amplitudes up to several thousand volts) will enter the network card through the long line, which may cause errors in the transmitted data signal, even break integrated circuit chip

Thirdly, the electromagnetic noise generated by the switching power supply, clock signal  will be transmitted to the surrounding space through the long line, forming a source of interference to other electronic instruments.

Finally, there is the problem of impedance matching. The characteristic impedance of the cable and the twisted pair are fixed. It is required that the internal resistance and load resistance of the data signal source connected to them are matched with the characteristic impedance of the long line. Otherwise, the two ends of the long line will be mismatched due to impedance. Producing a reflected interference signal also causes a bit error in the transmitted data signal.

In addition, in recent years, an additional task requirement has been put forward for the network cable. The long-distance power supply of the DC power supply to the electronic equipment in the remote area is obviously connected by a straight line. These problems cannot be solved, and even more Complete the newly added tasks.

After years of research by engineers, it is found that if a transformer is added to each end of the connecting line and the semiconductor integrated circuit load resistor, the above problem can be solved perfectly. And this transformer is our SMD lan transformer.What is the principle of a SMD LAN transformer?

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