31. GDT for RS-485 Bus Lightning Protection

RS-485 cables running 500+ meters between buildings act as long antennas that pick up lightning-induced voltage surges. These surges can be thousands of volts — instantly destroying the RS-485 transceiver chip.

A GDT at each port entry absorbs this energy. The 75V spark-over is well above the RS-485 operating range (−7V to +12V), so it stays inactive during normal communication. Through-hole mounting provides robust mechanical connection for industrial environments.

Required: 75V Spark-Over · ≥5kA (8/20µs) · 2-Pole · Through Hole · Littelfuse · RoHS

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) → 5kA or higher
• Number of Poles → 2
• Mounting Type → Through Hole
• Manufacturer → Littelfuse Inc.
• Part Status → Active

Tip:  A GDT alone provides primary protection for high-energy surges. For complete protection, pair the GDT with a downstream TVS diode to clamp residual voltage to a safe level for the transceiver.

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

➡ View Matching Parts — Littelfuse, GDT, 75V, ≥5kA, 2-Pole, Through Hole