Ethernet ESD Protection

Ethernet ICs are vulnerable to damage from Electrostatic Discharge (ESD). The fatal discharge may originate from a charged cable or a “human body”. Furthermore, devices used in telecommunications equipment may be exposed to lightning induced transients. The featured article and application notes below cover different aspects of Ethernet ESD protection, as well as information on our latest ESD protection circuits designed to provide maximum circuit protection for your Ethernet interfaces.

New DigiKey Product Training Module
Protecting Ethernet Interfaces from ESD, Cable Discharge, and Lightning Threats

This interactive training module focuses on providing an application insight into protecting Ethernet interfaces from transient voltage threats. Topics covered include:

  • an overview of the why the need for transient voltage protection has increased 
  • the types of transient voltage threats, including ESD, CDE, and Lightning
  • a discussion on how Transient Voltage Suppression (or TVS) devices function and what to look for in choosing a TVS component
  • Semtech TVS solutions and some real world Ethernet circuit protection applications

To view our Etherent Protection product training module, choose one of the options below (note that clicking on the links will take you to the DigiKey website):

Featured Article
Safeguard Ethernet Interfaces from Cable Discharges 

Protecting Ethernet interfaces from cable discharges can create a challenge for engineers because good protection must meet two criteria. First, and most important, a protective circuit must effectively clamp a transient to a safe voltage. Second, the protection circuit must present an acceptable capacitive load on high-speed differential transmission lines. Good planning and careful selection of transient voltage-suppression devices can adequately protect Ethernet interfaces from electrostatic discharges (ESDs) and cable discharge events.

> Download our "Ethernet ESD and CDE Protection" article

10/100 Ethernet ESD Protection

The Ethernet market is moving from 10 Base-T operating at 10Mbps to 100Mbps fast Ethernet. The original 10Base-T Ethernet chips were fairly large geometry CMOS products and they were not very sensitive to static overvoltage. Newer 10/100 Ethernet devices however have become extremely sensitive to latch-up or damage as IC manufacturers have moved to 0.35-micron and smaller line widths. Devices used in Ethernet switches and routers are also exposed to high-energy lightning induced transients.

In a typical system, the twisted-pair interface for each port consists of two differential signal pairs: one for the transmitter and one for the receiver. The transmitter input being the most sensitive to damage. The fatal discharge occurs differentially across the transmit or receive line pair and is capacitively coupled through the transformer to the Ethernet chip. The challenge is to find a TVS (transient voltage suppressor) that will clamp low enough as to prevent latch-up or damage to the Ethernet IC.

> Download our "10/100 Ethernet ESD Protection" application note

Gigabit Ethernet ESD Protection

Ethernet ports are highly susceptible to line-to-line or metallic surges. During a metallic surge, current will flow into one line, through the transformer and back to the source. As the current flows, it charges the secondary windings of the transformer. Once the surge is removed, the secondary winding will stop charging and will transfer its stored energy to the primary side where the PHY IC is located. Internal protection circuitry of Ethernet PHY chips is limited at best. It often consists of small rail-to-rail diodes or thick epi layers to increase the immunity of the device. Often the internal protection circuit is damaged during the initial discharge followed by damage to the CMOS structure after subsequent discharges. Catastrophic failures are easy to detect and identify. Latent failures are however very difficult to find and often manifest themselves as “bugs” and reliability problems.

Transient protection of a Gigabit Ethernet interface can be challenging. The high-speed data transmission requires the protection device to have low capacitance to prevent signal degradation and low clamping voltage to reduce stress on the protected IC.

> Download our "Gigabit Ethernet ESD Protection" application note

Ethernet ESD Protection for Ethernet Transceivers

IEC 61000-4-2 defines ESD immunity requirements for equipment which is shipped into the European Community. The standard defines test voltages as high as 15kV for air discharge (8kV contact discharge) and induced current as high as 30A. The test procedure requires that equipment be able to withstand ten pulses in both positive and negative polarity.

An electrostatic discharge to the shield of the coaxial connector causes an electromagnetic wave to propagate across the transceiver board interface to the circuit board. The wave travels along the metal traces which connect the shield to the PC board ground plane. The effects of circuit board trace inductance can result in voltage potentials greater than 1.5kV at the CDS pin. Voltage overstress of this magnitude can cause dielectric breakdown of the transceiver chip.

> Download our "ESD Protection for Ethernet Transceivers" application note

Featured Ethernet ESD Protection Products

View our product selector to compare and select parts for your Ethernet ESD protection application.