What exactly is an Ethernet transformer filter used for?
Time:2022-09-01
Views:441
In Ethernet equipment, when connecting RJ45 through PHY, a network transformer will be added in the middle. Some transformers have their center tap connected to ground. And when the power supply is connected, the power supply value can be different, 3.3V, 2.5V, and 1.8V are available. The role of this transformer is analyzed as follows:
1. Why do you connect different voltages when connecting to the power supply? This is also determined by the UTP port level specified in the PHY chip data used. What level is decided, you have to connect the corresponding voltage. That is, if it is 2.5v, it will be pulled up to 2.5v, and if it is 3.3v, it will be pulled up to 3.3v.
2. Why are some of the middle taps connected to the power supply? Some ground? This is mainly determined by the driving type of the UTP port of the PHY chip used. There are two types of driving, voltage driving and current driving. Voltage-driven need to be connected to the power supply; current-driven can directly connect a capacitor to the ground! Therefore, for different chips, the connection method of the center tap is closely related to the PHY. For details, please refer to the datasheet and reference design of the chip.
⒊ What is the function of this transformer, can it not be connected? Theoretically speaking, it is possible to directly connect to RJ45 without connecting a transformer.
works fine. However, the transmission distance is very limited, and when it is connected to a different level network port, it will also have an impact. And the external interference to the chip is also very large. When connected to a network transformer, it is mainly used for signal level
coupling. First, it can enhance the signal and make the transmission distance longer; second, the chip end is isolated from the outside, the anti-interference ability is greatly enhanced, and a great protection effect (such as lightning strike) is added to the chip; arrive
When the network ports of different levels (for example, some PHY chips are 2.5V, and some PHY chips are 3.3V), they will not affect each other‘s devices.
