- As the worldwide leader in circuit protection, Littelfuse offers POWR-GARD®, Teccor®, Wickmann®, Pudenz®, Hamlin®, PulseGuard® and SIDACtor® branded products, with a wide range of technologies such as Fuses, PTCs, GDTs, Varistors, TVS Diodes, TVS Diode Arrays (SPA®), Switching Thyristors, as well as reed switches, relays and sensors. Littelfuse products are backed by more than 85 years of technology innovation, industry leading technical support, design and manufacturing expertise. Littelfuse products are vital components in virtually every product that uses electrical energy, including automobiles, computers, consumer electronics, handheld devices, industrial equipment, and telecom/datacom circuits. 

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Go To Product Training Module Index Page

Digi-Key’s library of more than 2000 exclusive PTM Online… On Demand® product training modules is a collection of training tools created with you – the busy design engineer – in mind. They are provided with the cooperation of participating supplier partners. From this one source, you can learn about the latest products and technologies, download datasheets, check inventory, contact our technical staff, and place an order for same-day shipment.

These modules are available in audio and non-audio formats and listed by supplier in easy-to-find alphabetical order. Simply locate the module that interests you and click on your format of choice. We hope you find these tools useful, and with new modules added continuously, we invite you to stop back often to see what’s new.

Product Training Modules Online...On Demand® is a registered trademark of Digi-Key Corporation.

Updated PTM = Updated Product Training Module - PTM        New PTM = New Product Training Module - PTM

Module NamePreviewAudioNon-AudioDurationParts List
  • Ethernet Protection
8.6MB1.6MB10 minParts List
  • Fuseology- Introduction to Fuses
3.0MB944KB5 minParts List
  • High Power TVS Diode
5.4MB968KB10 minParts List
  • Introduction to SIDACtor Devices
8.5MB805KB35 minParts List
  • Metal Oxide Varistors
10.8MB4.3MB30 minParts List
  • PLED Devices - Open LED Protector
3.9MB579KB15 minParts List
Updated PTM
  • Protecting Network and Telecommunications Ports
7.3MB1.7MB10 minParts List
  • Reed Switch Basics
4.7MB450KB5 minParts List
  • Surge Protection LSP05 and LSP10 Series
2.8MB1.3MB5 minParts List
  • Transient Voltage Suppression (TVS) Diodes
6.8MB2.0MB20 minParts List
  • TVS Diode Arrays - ESD Suppressors for I/O Interfaces
Play7.5MB2.1MB15 minParts List
  • Varistor UL1449 3rd Edition Safety Agency Update
5.8MB943KB15 minParts List

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TVS Diode Arrays with High-Speed Protection SP4044/SP4045 SeriesTVS Diode Arrays with High-Speed Protection SP4044/SP4045 Series - SP4044/SP4045 series TVS Diode Arrays (SPA® Diodes) from Littelfuse protect sensitive electronics from destructive electrostatic discharges (ESD) and lightning-induced surge events. Low capacitance diodes are integrated with an additional Zener diode to protect each I/O pin against ESD and high-surge events.  More...

TVS Diode Array for Portable Electronics SP3312T SeriesTVS Diode Array for Portable Electronics SP3312T Series - Littelfuse's SPA family of TVS diode array devices are designed to protect electronics from very fast and often damaging voltage transients, such as lightning and electrostatic discharge (ESD).  More...

Brochures and Catalogs

Fuse Products Fuseholder Selection Guide TVS Diode Products PTC Products
Fuse Products Fuseholder Selection Guide TVS Diode Products
(eBook Format)
PTC Products
GDT Products Varistor Products TVS Diode Arrays Thyristor Products
GDT Products Varistor Products TVS Diode Arrays
(eBook Format)
Thyristor Products
(eBook Format)
SIDACtor Products  Hamlin Reed Switch Catalog Protection Relay & Controls Solar Products
SIDACtor-Products Hamlin Reed Switches Protection Relay & Controls Solar Products
POWR-GARD® Fuse Sensor Product    
POWR-GARD® Fuse Sensor Product    

Mobile App

Littelfuse eBook The eBook mobile app is available for both Apple and Android devices. Visit the App Store or Google Play to install the free "Littelfuse Catalog" app.


Selection Guides

SPICE Models

Using SPICE Models is the standard way to simulate circuit performance prior to the prototype stage as an additional step of testing to ensure that a circuit works properly before investing in prototype development. The models provided here were developed (or revised) using WinSpice, a port of Berkeley Spice3F4 to Win32, and should be compatible with most SPICE2 or SPICE3-based circuit simulators (such as PSPICE).

TVS Diode SPICE Models
PulseGuard SPICE Models
SIDACtor® SPICE Models
Varistor SPICE Models
Thyristor SPICE Models
More about Littelfuse

Littelfuse - Since Edward V. Sundt founded Littelfuse in 1927, we've been driven by innovation. Sundt invented the first small, fast-acting protective fuse to prevent sensitive test meters from burning out. From that pioneering first step, our company has gone on to define the standards of the circuit protection industry. In the 1960s, we developed sub-miniature fuses for NASA, which were mission-critical components of the American space program. And in 1976, we introduced the groundbreaking Autofuse® Fast-Acting Fuse for General Motors. Within eight years, it was being designed into vehicles all over the world. We again revolutionized automotive fuse protection in 1986 with the debut of the space-saving MINI®. Its smaller design allowed for the additional protection of on-board electronic accessories. Recently, we introduced the world's smallest high surge current protection thyristor, the Teccor Q2L series "C-Rated" SIDACtor device. And we continue to set new benchmarks. As the world leader in circuit protection, Littelfuse possesses nine core technologies, as well as some of the industry's most respected brands - Teccor, Wickmann, Hamlin, and Pudenz. In addition, we're doing business all over the world.

Hamlin Hamlin, Inc. is a leader in sensor technology, providing standard products and custom solutions for leading global manufacturers in the automotive, electronics and industrial markets. Littelfuse acquired Hamlin in 2013.
Concord Semi Concord Semiconductor is a leading Taiwan-based designer and manufacturer of TVS diodes and other overvoltage circuit protection products that protect equipment from high voltage/high energy transients. Littelfuse acquired Concord Semiconductor, based in Taiwan, in 2006.
Pudenz The Pudenz brand of automotive circuit protection products includes blade fuses, bolt-down fuses, fuse-holders and aftermarket fuse products. Littelfuse acquired the Pudenz brand as part of its acquisition of Heinrich Industrie of Witten, Germany, in 2004.
Smart Glow Smart Glow automotive blade fuses feature an indicator light that glows when the fuse is blown, saving time in troubleshooting an open circuit. Smart Glow fuses are sold through leading national automotive aftermarket retailers and distributors. Littelfuse acquired the Smart Glow line from Catalina Performance Accessories of Montainburg, Arkansas, in 2006.
Teccor Teccor Electronics has a market-leading line of overvoltage transient suppression products. It has the number-one market share position in North America and is in the top three globally for both of its product categories. Littelfuse acquired Teccor of Irving, Texas, in 2003.
Wickmann Prior to being acquired by Littelfuse, Wickmann was a leading manufacturer of circuit protection components for the consumer electronics, industrial electronics, telecommunications and data processing markets for more than 80 years. Littelfuse acquired the Wickmann brand as part of its acquisition of Heinrich Industrie AG of Witten, Germany, in 2004.
Littelfuse Press Room

Chicago Innovation Award Winner Littelfuse varistors recognized for advanced technology

The TMOV technology used in outdoor LED lighting and solar power applications optimize designs for safety and long-term reliability.

Learn more about the winner

Hamlin, Inc. Littelfuse Announces Acquisition of Hamlin

"The acquisition of Hamlin is a major step forward in our strategy to build a global, automotive sensor platform", read more about the acquisition.

Circuit Protection

Circuit Protection Application Matrix
Offers comprehensive overview of overcurrent protection and overvoltage suppression devices available, as well as a guide to choosing appropriate device type for a specific application

Reed Switches/Relays

AT vs mT and Gauss
What magnetic strength will activate a reed switch. Understanding the terms AT, mT and Gauss

Modifying Reed Switches
Importance of proper bending and cutting of leads on a Glass Reed Switch

Soldering Temperatures
Soldering recommendations for reed relays and reed switches

Magnetic Sensing in Washing Machines

Rice Cooker Lid Lock

Flow Sensing in Tankless Water Heaters

Lighting Protection Devices

LED Lighting SPD Module Design and Installation Guide
Design Guide for the LSP series SPD Modules, part selection and importance of adding this module to LED lighting applications.

PLED Protecting LEDS in Product Designs
White paper covers entire LED circuit protection portion of the product design, tips and guidelines.

PLED Open LED Protection for Light Strings
Using the PLED in LED strings, application information.

ESD and Transient Protection

USB 3.0 Port ESD Circuit Protection
Selecting the right TVS Diode Array for USB 3.0.

Ethernet Port Lightning, ESD and EFT Protection
Selecting the right TVS Diode Array for Ethernet Ports.

Transient Suppression Devices and Principles AN9768
Discusses two major categories of transient suppressors: attenuation and diversion of transients.

Selecting an Appropriate ESD Device
Guidance on ESD devices for designers looking for a successful first pass design.

Tips for Enhancing ESD Protection
Various techniques a designer can employ in meeting ESD Testing.

SP72x Protection Arrays Meeting ESD (IEC 61000-4-2) AN9612
Covers IEC 61000-4-2 ESD immunity and transient current capability for the SP72X Series protection arrays.


Fundamental Characteristics of Teccor® Thyristors AN1001
Presents the basic fundamentals and terminology of SCR, Triac, Sidac, and Diac thyristors.

Phase Control Using Teccor® Thyristors AN1003
Fundamentals of SCR and Triac phase controls, shows how this is possible.

Gating, Latching, and Holding of Teccor® SCRs and Triacs AN1002
Describes how the SCR and Triac parameters are related. Helps users select best operating modes for various circuit applications.

Miscellaneous Design Tips and Facts for Teccor® Thyristors AN1009
Relationship of IAV, IRMS, and IPK, dv/dt Definitions, gate terminations, Impulse waveform, failure modes and more.

Maximum Ratings and Characteristics for Teccor® Thyristors AN1008
Explains maximum ratings and describes the irreversible damage that may occur and how to avoid such issues.

Triac Protection
SIDACtor device used to protect thyristors being subjected to excessive peak off-state voltage.

Data Line Protectors
SIDACtor device used in the protection of data lines (such as Ethernet and RS-232).

LAN / WAN Protectors
SIDACtor device for 10/100Base-T Protection, compliant to GR1089 intra-building design.


Littelfuse Varistors: Basic Properties, Terminology and Theory AN9767
Describes the basic electrical properties of varistors.

Varistor Testing AN9773
Details the common tests of varistor parameters and describes suitable test methods using simplified test circuits.

The ABCs of MOVs AN9311
Guide for MOV products, A is for Application, B is for Basics, C is for Common questions.

The ABCs of Multilayer Suppressors AN9671
Guide for Multilayer MOV products, A is for Application, B is for Basics, C is for Common questions.

"ML" Multilayer Surface Mount Surge Suppressors AN9108
Applications, construction and capabilities of ML, MLE, MLN and AUML version multilayer suppressor.

Littelfuse Varistor Design Examples EC638
Common application examples, and illustrating the solution process for the appropriate varistor.

Protection Relay and Controls

Relay Accessories
Browse Protection Relay accessories

Network Support
Network communications support files for Littelfuse Startco relays

Online Demos & Tools
Learn more about using and programming Littelfuse Startco relays with online user interface demos

View Protection Relay product videos

Technology Solutions
Fuse Holders, Fuse Blocks, and Fuse Clips
Fuse Holders, Fuse Blocks, and Fuse Clips (HBC) - Enable easy fuse installation and replacement with Littelfuse's comprehensive line of fuse blocks, fuse holders, and fuse accessories for automotive, electronic, and industrial applications.
SPA Family of TVS Diode Arrays
SPA Family of TVS Diodes Arrays - Littelfuse SPA family of TVS diode array devices are designed to protect electronics from very fast and often damaging voltage transients, such as lightning and electrostatic discharge (ESD).
TVS Diodes
TVS Diodes - Littelfuse TVS diodes are used to protect semiconductor components from high-voltage transients. The p-n junctions of these devices have larger cross-sectional areas than those of normal diodes, allowing them to conduct large currents to ground without sustaining damage.
TVS SMD Diode Kits
TVS SMD Diode Kits - Digi-Key has created kits to cover a broad range of TVS diodes offered by Littelfuse. Ranging from industry standard package sizes of SMA to SMC with wattage ratings starting at 400 W and going as high as 3000 W in compact surface mount packages, these TVS diodes are designed to protect sensitive electronic equipment from voltage transients in such applications as telecommunications, computer, industrial and consumer electronics.
PLED Series SMD LED Array Protectors
PLED Series SMD LED Array Protectors - Littelfuse PLED Series is a voltage triggered electronic shunt device that provides a current bypass in the case of a single LED failing into an open circuit condition.
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