RJ45 interface protection circuit

Ethernet port lightning protection design requirements:

Meet the requirements of European CE certification, American FCC certification and Japanese VCCI certification. At the same time, the lightning protection requirements of Ethernet ports meet domestic requirements; specifically implement the following standards:

EN55022, EN55024, FCCPART15, ​​ETSIEN300386, EN60950, UL60950, etc.

Design focus:

Due to the high interface rate, the port filtering design and PCB design are the design focuses of this product. In addition, the selection control of key components is strengthened to ensure that the components meet the EMC safety requirements of the entire machine.

■This solution can achieve a differential mode 3KA (8/20μs) impulse current level, fully meeting the interface lightning protection requirements. The insertion loss is less than 0.3dB, which has little impact on Ethernet transmission signals.

■The front-stage protection is LT-B3D230L SMD triode ceramic gas tube. For coaxial cable transmission, it is LT-5G090L device.

■The resistor plays a decoupling role, allowing the front and rear protection circuits to cooperate with each other. The resistance value should be as large as possible while ensuring the signal, so as to achieve better lightning protection performance.

■The back stage is SLVU2.8-41. It can perform differential mode protection for two balanced lines, that is, only one device is used for one network port (receive, send); 2. The junction capacitance C<6pF, which can meet the transmission rate requirements of 100M network port; 3. It has a certain current capacity, with a maximum impact current of 24A (8/20μs), which meets the requirements of 500V surge test;