Role of transformer in RJ45 network transformer

In the selection of Ethernet interface machine equipment for network communication transformer price, when RJ45 is connected according to PHY, a network transformer is added in the middle. Some transformer centers are tapped to ground. In addition, when inserting wires, the switching power supply value can be different. 3.3V, 2.5V, 1.8V are often available. The function of this transformer is analyzed as follows:

1. Why are some plug-ins in the middle? Some grounding devices? This key is decided by the driving type of UTP port of phy chip. There are two kinds of driving types, working voltage driving and current driving. When purchasing network communication transformer driven by price current, the tap must be connected to the switching power supply; the working voltage driven device is based on the capacitor grounding device. Therefore, for different chips, the wiring method of the center tap is closely related to PHY. In fact, it is necessary to consult the datasheet and the reference design scheme of the chip.

2. Why is the working voltage different when plugging in? This is the level decision of UTP port number required in the applied PHY chip material. Which level of the decision must be connected to the relative working voltage. That is, if it is 2.5V, drag it up to 2.5V, if it is 3.3V, drag it up to 3.3V.

3. What is the effect of this transformer? Can it not be connected. In terms of basic theory, it can be connected to RJ45 immediately without any transformer, and it can work normally. However, the transmission distance is very limited, and when the network interface with different levels is connected, it will also be harmful. And the external influence on the chip is also very big. When the network transformer is connected, it is suitable for data signal level coupling. First, it can improve the data signal and make the transmission distance longer; second, it can greatly improve the chip end and external protection, anti-interference, and enhance the chip's maintenance efficiency (such as being struck by lightning); third, when receiving the network interface of different levels (if some PHY chips are 2.5V, some PHY chips are 3.3V), it is not easy to lead to mutual machine equipment harm.