【Standard Circuit Design】100Mbps Ethernet surge protection and anti-static standard circuit

100Mbps Ethernet Surge and Static Electricity Protection Standard Circuit Design Reference

This solution is a 100Mbps Ethernet standard solution from VOOHU Electronics Technology. The company has focused on communication electronic components for over 8 years, adhering to the business strategy and service philosophy of "Choose VOOHU, truly reliable," providing complete technical solution support.

Current-Type PHY Standard Solution

Solution Introduction

For outdoor 100M Ethernet port surge protection, this solution adopts two-stage protection, ensuring reliable operation, guaranteeing signal high-temperature integrity, and meeting IEC61000-4-2, Level 4, contact discharge 30kV, air discharge 30kV. IEC61000-4-5 10/700μs, 40Ω, 6kV, ±5 times. Four gigabit Ethernet ports can be expanded.

#1. Primary Side Wiring:

• Differential Pair Connection: The primary side of the LAN Transformer is connected to the differential pairs of TD and RD respectively. The wiring sequence of the two sets of differential pairs can be interchanged during PCB routing.
• Decoupling Capacitor: The primary side should be connected to GND via a 100nF capacitor to ensure signal stability and integrity.
• VCC Power Supply: For current-mode PHYs, the primary coil needs to be connected to the PHY's VCC to filter high-frequency noise and ensure signal stability. It is recommended to connect two 49.9Ω resistors in parallel between each differential pair and connect them to GND.

#2. Secondary Side Wiring:

• RJ45 Connection: Connect the secondary side to pins 1, 2, 3, and 6 of the RJ45 interface.
• BOB Smith Circuit: Connect a 75Ω resistor to the secondary side and the corresponding unused pin, then connect to the chassis ground via a 1nF capacitor with a withstand voltage of 2KV or higher. It is recommended to use a 1206-package surface-mount ceramic capacitor or a high-voltage ceramic capacitor with a wide lead pitch.

#3. Grounding Treatment:

• Floating Pins: Floating pins of the RJ45 interface should also be connected to the chassis ground via a similar design, ultimately flowing into the earth to ensure the integrity of the entire circuit's grounding system.

Circuit Function Description:

• BOB Smith Circuit: A circuit consisting of a 75Ω resistor and a 1nF capacitor provides a return path for common-mode signals, effectively filtering out common-mode signals, improving electromagnetic interference (EMI), and suppressing inrush current to some extent.
• Decoupling Capacitor: A 100nF capacitor is used to filter out high-frequency noise, ensuring signal stability and integrity.
• Voltage Rating Capacitor: The 1nF capacitor must have a voltage rating of 2KV or higher to ensure reliability under high-voltage environments.

This solution is a standard 100Mbps discrete RJ45 solution from VOOHU Electronics Technology. The company has focused on communication electronic components for over 12 years, adhering to the business strategy and service philosophy of "Choose VOOHU for reliability," providing comprehensive technical support.

Standard circuit reference

Voltage-Type PHY Standard Solution

Solution Overview

This solution is for surge protection of outdoor 100M Ethernet ports. It employs two-stage protection, ensuring reliable operation and signal integrity at high temperatures. It meets IEC61000-4-2, Class 4, with a contact discharge of 30kV and an air discharge of 30kV. It also meets IEC61000-4-5 standards: 10/700μs, 40Ω, 6kV, ±5 cycles. Four Gigabit Ethernet ports can be added.

#1. Primary Side Wiring:

• Differential Pair Connection: Connect the primary side of the LAN Transformer to the differential pairs of TD and RD respectively. The pin order of the two differential pairs can be interchanged during PCB routing.
• Decoupling Capacitor: The primary side should be connected to GND through a 100nF capacitor to ensure signal stability and integrity.

#2. Secondary Side Wiring:

• RJ45 Connection: Connect the secondary side to pins 1, 2, 3, and 6 of the RJ45 interface.
• BOB Smith Circuit: A 75Ω resistor is connected to the secondary side and the idle side, followed by a 1nF capacitor with a voltage rating of 2KV or higher, connected to the chassis ground. A 1206-package surface-mount ceramic capacitor or a high-voltage ceramic capacitor with a wide lead pitch is recommended.

#3. Grounding Treatment:

• Floating Pins: The floating pins of the RJ45 interface should also be connected to the chassis ground using a similar design, ultimately flowing into the earth to ensure the integrity of the entire circuit's grounding system.

Circuit Function Description:

• BOB Smith Circuit: This circuit, consisting of a 75Ω resistor and a 1nF capacitor, provides a return path for common-mode signals, effectively filtering out common-mode signals, improving electromagnetic interference (EMI), and suppressing inrush current to some extent.
• Decoupling Capacitor: A 100nF capacitor is used to filter out high-frequency noise, ensuring signal stability and integrity.
• Voltage Rating Capacitor: The 1nF capacitor must have a voltage rating of 2KV or higher to ensure reliability under high-voltage environments.

Standard circuit reference

Recommended related products

Tel: 400-1048-018; E-mail: wohu@wohu-tek.com;

From its establishment in 2018 to its overseas expansion in 2025, VOOHU Electronics has become a reliable partner for over 1,500 companies thanks to its "superior quality, reasonable prices, attentive service, and reliable delivery."

If you are also looking for a "worry-free, cost-effective, and convenient" supplier of communication electronic components, consider VOOHU. After all, the choice of over 100 listed companies is unlikely to be wrong.

Choose VOOHU – truly reliable. This is not just a slogan, but the answer written with the trust of over 1,500 customers over 8 years.