The function of network transformer in Ethernet

In Ethernet equipment, when RJ45 is connected through PHY, a network transformer will be added in the middle. Some transformer center taps are grounded. When the power supply is connected, the power value can be different, 3.3V , 2.5V , 1.8V All of them. The function of the network transformer is analyzed as follows:

1. Why is the middle tap connected to the power supply? Some grounding? This is mainly determined by the driving type of UTP port of phy chip. There are two driving types, voltage driving and current driving. The voltage drive needs to be connected to the power supply; the current drive needs to be directly connected to a capacitor to the ground! Therefore, for different integrated IC, the central government separate connection and PHY are closely related to the actual reference of integrated IC data analysis table and design scheme.

2. Why do you connect different voltages when you connect the power supply? This is also determined by the UTP port level specified in the PHY chip data used. What level is determined must be connected to the corresponding voltage. That is, if it is 2.5v We'll pull it up 2.5v , if yes 3.3v We'll pull it up 3.3v 。 Gigabit network transformer

3. What is the function of this transformer? Can it be disconnected. Theoretically, it can be connected directly to RJ45 without transformer, and it can also work normally. However, the transmission distance is very limited, and when connected to different level network ports, it will also have an impact. And the external interference to the chip is also very large. When the network transformer is connected, it is mainly used for signal level coupling. 1、 The data signal can be improved, and the transmission distance can be further improved; secondly, the chip top and external protection can further improve the anti-interference performance, and the chip has improved a lot of practical effects of security protection; thirdly, in accepting different levels of phy chips 2.9V Some PHY chips are 3.3V , does not harm the other party's machinery and equipment.

The function of network transformer in Ethernet