PPTC Resettable Fuse for PoE Ethernet Port Protection

Question

Problem: PPTC Resettable Fuse for PoE Ethernet Port Protection. Solve this hands-on electronics task on EWskills.

Accepted Answer

1. Component Purpose

PoE supplies up to 57V through the Ethernet cable. If a fault occurs on the board’s PoE input, the high voltage can drive dangerous current levels. A PTC fuse limits this by tripping on overcurrent.

The critical requirement is voltage rating ≥60V. Standard 1210 PTC fuses max out at ~30V. A 1812 package is required because it supports higher voltage ratings suitable for PoE.

Hold Current: Device draws 350mA. With derating: Ih = 450mA to 700mA

Required: Polymeric · Ih 450–700mA · ≥60V · Imax ≥5A · 1812 · SMD · Littelfuse

2. How to Find It on DigiKey

Go to DigiKey.com → Circuit Protection → PTC Resettable Fuses

Apply these filters:

Current - Hold (Ih) → 450mA to 700mA range
Voltage - Max → 60V or higher
Package / Case → 1812
Mounting Type → Surface Mount
Manufacturer → Littelfuse Inc.
Part Status → Active

Important: Do not use a 1210 PTC fuse for PoE. Most 1210 PTCs are rated ≤30V — far below the 57V PoE supply. The 1812 package is required for the higher voltage rating.

3. Key Specifications & What They Mean

Specification	Required	Why
Type	Polymeric	Standard resettable PTC.
Hold Current	450–700mA	350mA load + thermal derating.
Voltage Max	≥60V	PoE max is 57V; needs margin.
Current Max	≥5A	Survives PoE fault current.
Package	1812 SMD	Required for ≥60V voltage rating.
Manufacturer	Littelfuse	Company AVL requirement.
Temp Range	−40°C to +85°C	Standard operating range.
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, PTC, Ih 450–700mA, ≥60V, 1812 SMD

16. PPTC Resettable Fuse for PoE Ethernet Port Protection