ESD/EOS solution for Wi-Fi 6E router products

IEEE published the latest Wi-Fi 6E in 2020 in response to the rapid development of wireless network. The extension of Wi-Fi 6, it covers the 6GHz band in addition to the previously supported 2.4GHz and 5GHz bands, mainly because of communication interference and jammed frequency bands due to the wide spectrum of products on 2.4GHz and 5GHz bands. For this, the 6GHz band was added in Wi-Fi 6E in the hope to deal with these nuisances. The Wi-Fi 6E supports 7 channels with bandwidth as wide as 160MHz, while being capable of more transmissions at greater rate. When it comes to transmission rate, the maximum transmission has been increased to 9.6 Gbps from 6.9 Gbps of previous Wi-Fi 5, more than enough to allow us to watch high-resolution 4K videos and play online games over wireless network through much smoother streaming.   

The improvement and updates of Wi-Fi version prompt the upgrade of router product performance. A router usually comes with several interfaces, such as LAN, USB and Wi-Fi antenna. For LAN, the transmission has been improved from the previous 1 Gbps to 2.5G/5Gbps.   

A router may be located in an outdoor environment where the router is prone to EOS energy interference. Product development engineers have to select a TVS protection element with greater resistance to ESD/EOS during circuit design, or the router system is vulnerable when subject to an external EOS energy interference. This is particularly true in the case of LAN PHY. As the increasingly advanced manufacturing proAcess of semiconductors inevitably makes the high-speed 2.5G/5Gbps LAN PHY far more vulnerable to its 1Gbps counterpart, it has become a trend to add an ESD/EOS production element at the PHY side during product design. An ESD/EOS protection solution designed specifically for Wi-Fi 6E routers will be described later.   

For the LAN protection, there are line-to-line and line-to-GND protections, as shown in Figure 1. 

Figure 1 Recommended line-to-line and line-to-GND TVS configurations for LAN port

For the line-to-GND protection of 2.5G/5Gbps LAN, the AZ1243-04F is recommended. This 4-channel TVS array features 0.5 pF (Typ.) for the I/O-to-GND parasitic capacitance, and the single ESD resistance reaches up to Contact ±25kV/Air ±27kV. The parameter that has the greatest influence on the system ESD production is the ESD clamping voltage, which is merely 8.5V with ESD=8kV.     

On the other hand, AZ5B0S-01F is recommended for line-to-GND 2.5G/5Gbps LAN protection, as the element features parasitic capacitance as low as 0.18pF (Typ.). It also features an Ipp resistance equivalent to IEC61000-4-5 Lightning 7A(8/20μs). With Ipp(8/20μs) at 7A, the TVS’s surge clamping voltage is 4V.   

When a router is under ESD test, the system may crash if the LAN PHY power supply is sensitive to ESD. In this case, a TVS is placed at the LAN PHY power supply side for better ESD protection. Normally, the LAN PHY voltage is 1.8/2.5V. Amazing Microelectronic has a wide range of ESD/EOS solutions available for your disposal, as shown in Table 1.   

We see Wi-Fi applications almost everywhere. It is recommended to incorporate TVS elements in the circuit as early as in the product design stage. It not only prevents the possible failure to pass subsequent ESD/EOS test, but also minimizes product return for repair due to surge damage in the market. 

Table 1 Complete ESD/EOS solution range for Wi-Fi6E routers