GDT for Ethernet Port Lightning Protection

Question

Problem: GDT for Ethernet Port Lightning Protection. Solve this hands-on electronics task on EWskills.

Accepted Answer

1. Component Purpose

Outdoor Ethernet cables to IP cameras are exposed to lightning. A surge on the cable pairs can destroy the Ethernet PHY chip and PoE circuitry, which are very sensitive semiconductors.

A GDT placed on each cable pair at the port entry absorbs the high-energy surge before it reaches the board. The 75V spark-over is above the maximum PoE voltage (57V per IEEE 802.3af/at), so the GDT stays inactive during normal PoE operation.

Outdoor Ethernet requires ≥10kA surge rating because the cable runs can be long and directly exposed to lightning-induced currents.

Required: 75V Spark-Over · ≥10kA (8/20µs) · 2-Pole · Surface Mount · Littelfuse · RoHS

2. How to Find It on DigiKey

Go to DigiKey.com → Circuit Protection → Gas Discharge Tube Arresters (GDT)

Apply these filters:

Voltage - DC Spark Over (Nom) → 75V
Impulse Discharge Current (8/20µs) → 10kA or higher
Number of Poles → 2
Mounting Type → Surface Mount
Manufacturer → Littelfuse Inc.
Part Status → Active

Tip: Each Ethernet port has 4 cable pairs. You need one 2-pole GDT per pair. The user selects the correct single GDT component; the BOM quantity depends on the number of pairs to protect.

3. Key Specifications & What They Mean

Specification	Required	Why
Spark-Over Voltage	75V	Above PoE max (57V); fires only on surges.
Surge Current	≥10kA (8/20µs)	Outdoor cables need heavy surge handling.
Number of Poles	2	Protects one cable pair per GDT.
Mounting	Surface Mount	Compact for Ethernet port PCB layout.
Manufacturer	Littelfuse	Company AVL requirement.
RoHS	Yes	Compliance required.

4. Selecting a Safe, Production-Ready Part

The filtered list will show matching parts. Before you pick one, check: Is it Active? Is stock available? Is the manufacturer reputable? Is a datasheet available?

Full checklist: How to Select a Safe, Production-Ready Component — EWskills Guide

5. Filtered DigiKey Link

➡View Matching Parts — Littelfuse, GDT, 75V, ≥10kA, 2-Pole, SMD

44. GDT for Ethernet Port Lightning Protection