ESD/EOS Protection Solution for Wi-Fi 8 Router Products

The Wi-Fi 8 (IEEE 802.11bn) specification is still in the draft stage and is expected to be officially finalized in 2028. Based on the currently released specifications, Wi-Fi 8 is nearly identical to Wi-Fi 7 in terms of transmission speed, frequency bands, and channel bandwidth. Its transmission speed can reach up to 46 Gbps, and it supports the 2.4 GHz, 5 GHz, and 6 GHz bands, with a maximum channel bandwidth of 320 MHz, 4096-QAM modulation, 16 spatial streams, MU-MIMO, and multi-OFDMA technologies. However, Wi-Fi 8 has shifted its focus from pursuing higher transmission speed to improving connection stability and reliability, making it more suitable for applications such as AR/VR, industrial IoT, and AI. For AP/router products, R&D engineers must consider not only wireless and wired signal quality during product design, but also ESD/EOS protection, which is an important design consideration that cannot be overlooked. 

At present, some major networking brands have already raised their ESD test requirements to 8 kV contact discharge and 15 kV air discharge. Since some AP products may be deployed in outdoor environments, surge testing for Ethernet ports is also required in addition to conventional ESD testing. Surge testing is mainly divided into two modes: common-mode surge and differential-mode surge. The most common surge test waveform is 8/20 us. Because surge energy is much higher than ESD energy, it is especially important to place appropriate protection components on the Ethernet interface. 

As Wi-Fi 8 transmission speed increases to 46 Gbps, the Ethernet ports of AP/router products are also gradually moving toward high-speed transmission specifications such as 2.5 Gbps, 5 Gbps, and 10 Gbps. Therefore, when selecting ESD/EOS protection components, designers must consider not only the protection capability, but also whether the parasitic capacitance of the protection component itself may affect the signal integrity and transmission quality of a 10 Gbps network. The following section introduces ESD/EOS protection countermeasures for AP/router products. For line-to-ground ESD/EOS protection design on 2.5 Gbps, 5 Gbps, and 10 Gbps Ethernet ports, AZ1223-04F is recommended. This device is a 4-channel ESD/EOS protection component in a DFN2510P10E package. Only two devices are required to fully protect the eight signal lines of an Ethernet port. Its I/O-to-ground parasitic capacitance is only 0.2 pF (typical), its standalone ESD immunity can reach Contact +/-12 kV and Air +/-15 kV, and it also provides an IEC 61000-4-5 Lightning (8/20 us) Ipp withstand capability of 8 A. For ESD clamping voltage, which has the greatest impact on system-level ESD protection effectiveness, AZ1223-04F provides a clamping voltage of only 8.5 V at 8 kV ESD, effectively preventing PHY damage caused by ESD/EOS events. 

For line-to-line EOS protection, AZ5B0S-01F is recommended. This device is provided in a DFN0603P2Y package, with a parasitic capacitance of only 0.18 pF (typical), and offers an IEC 61000-4-5 Lightning (8/20 us) Ipp withstand capability of 7 A. At an Ipp (8/20 us) level of 7 A, the surge clamping voltage of the TVS is 4 V, providing excellent system-level EOS protection performance.

Figure 1. Recommended TVS placement circuit for LAN port line-to-line and line-to-ground protection

The above describes the ESD/EOS protection solution for Ethernet ports. In addition, the following situations are commonly encountered during product ESD testing: 

1. During ESD air-discharge testing, the LAN PHY LED control signal line or GPIO signal may be affected by ESD, resulting in signal abnormalities. It is also recommended to place ESD components at these locations to prevent this issue. 

2. When performing ESD testing on the GND of a USB or RJ45 port, LAN PHY malfunction may occur due to GND disturbance. In this case, a TVS can be placed at the LAN PHY power supply to strengthen ESD protection. 

For the complete ESD/EOS protection solution for Wi-Fi 8 AP/router products from Amazing IC, please refer to Table 1. A properly implemented system design can not only meet ESD/EOS test requirements, but also help prevent customer returns and repairs after products are sold to end users, thereby enhancing brand value in the market.

Table 1. Complete ESD/EOS protection solution for Wi-Fi 8 router products