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Bourns Circuit Protection
S E L E C T I O N G U I D E
Telecom
Circuit Protection
Circuit Protection Solutions The Bourns Mission
Our goal is to satisfy customers on a global basis
while achieving sound growth with technological
products of innovative design, superior quality
and exceptional value. We commit ourselves to
excellence, to the continuous improvement
of our people, technologies, systems, products
and services, to industry leadership and to
the highest level of integrity. Introduction
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Applications - What Protection do you Need?
What is a Surge? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
What is Protection? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Lightning - Global and Different . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Where will the System be Used? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Coordination is No Longer Optional . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
System Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Application - Central Ofce (CO) and Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Application - Customer Premise Equipment (CPE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Digital Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
Useful Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Network Diagram
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 & 17
Technology - Which Protection Technology is Right for the Equipment?
The Basics - Overvoltage and Overcurrent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
What Happens After a Surge or if the Device Fails? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Speed and Accuracy are Major Factors in Determining Equipment Stress Levels . . . . . . . . . . . . . . . . . . . .19
Technology Selection - Overvoltage Protectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
Gas Discharge Tubes (GDTs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
Thyristor-Based Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
Metal Oxide Varistors (MOVs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
Transient Voltage Suppressors (TVSs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
Technology Selection - Overcurrent Protectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
Positive Temperature Coefcient (PTC) Thermistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
Fuses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
Heat Coils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
Line Feed Resistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
Thermal Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
Modes of Overvoltage Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
Technology Selection - Integrated Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
Multi-Stage Protectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
Integrated Line Protection Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
Product Selection Guides
Gas Discharge Tubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32
Multifuse
®
PPTC Resettable Fuses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
TISP
®
Thyristor Surge Protectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
Surge Line Protection Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
Telefuse Telecom Fuses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
Index
1 2
Bourns is pleased to present this comprehensive
guide to Telecom Circuit Protection, encompassing
our broad range of technologies and products. This
guide will provide the background information and
selection recommendations needed to ensure that
your next project achieves the level of cost-effective
eld reliability demanded by todays customers.
Bourns commissioned a survey of Telecom Circuit
Protection users worldwide to determine their prior-
ities and needs. We found that reliability, technical
and design support, and exemplary knowledge of
protection technology were by far the three most
cited items. Bourns is committed to meeting each of
these three requirements:
Reliability
Reliability requires an understanding of
the capabilities and specications of circuit protection
technology. Bourns has a global reputation for quality
products, and our circuit protection devices have
consistently demonstrated reliability in eld applica-
tions. Bourns is committed to the complete support
of a circuit protection solution for the life of a
program.
Introduction
Technical and Design Support
Bourns team of
specialized Sales and Field Application Engineers are
ready to bring additional in-depth expertise to your
next project. Through our interactive website and
customer service locations, Bourns is always available
to answer circuit protection design questions and
provide valuable assistance and support.
Knowledge of Protection Technology
Bourns
boasts the industrys widest range of Telecom over-
voltage and overcurrent protectors. Our active
involvement in international protection standards
organizations ensures world-class technology and
applications expertise.
Bourns continues to develop an innovative range of
integrated circuit protection products using our
knowledge and expertise to combine multiple
technologies into optimized single devices designed
to save both cost and board space. Whether you need
a single product or a complete protection solution,
Bourns Telecom Circuit Protection team is there to
help you. We look forward to working with you. Communication systems are vulnerable to electrical
damage from lightning or other surges. As systems
become more complex, they also become more
vulnerable. Balancing the cost, standards compliance
and eld reliability of protection is both a commercial
and technical challenge, compounded by the addi-
tional performance constraints of modern digital
networks such as xDSL.
This section is intended to outline those challenges,
illustrate the fundamentals of protection and identify
those international standards relevant to specic
applications. The next section will examine individual
protection technologies and their selection.
Bourns engineers have helped designers with major
projects in every region of the world, successfully
protecting hundreds of millions of telephone circuits.
Our uniquely broad range of protection solutions
enables us to identify the most suitable technology
for each application. Whether the goal is to achieve
standards compliance or tackle a specic eld prob-
lem, Bourns experience and product offering are the
solution to a myriad of design requirements.
are signicant for device survival and safety. Direct
contact to the AC (power cross) causes high currents,
while lower currents result from power inductio