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1 Confidential and Proprietary to Littelfuse, Inc. © 2007 Littelfuse, Inc. All rights reserved. Telecom GDT Training Training Agenda 1. GDT Definition and Telecom Circuit Protection 2. GDT Characteristics and Device Physics 3. GDT Telecom Applications Protection Example 4. GDT Telecom Applications Product Selection 5. Littelfuse GDT Product Road Map 6. Telecom GDT Technology Challenges

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Page 1: Training Agenda - · PDF fileTelecom GDT Training Training Agenda 1. GDT Definition and Telecom Circuit Protection 2. GDT Characteristics and Device Physics 3. GDT Telecom Applications

1 Confidential and Proprietary to Littelfuse, Inc. © 2007 Littelfuse, Inc. All rights reserved.

Telecom GDT Training

Training Agenda

1. GDT Definition and Telecom Circuit Protection

2. GDT Characteristics and Device Physics

3. GDT Telecom Applications Protection Example

4. GDT Telecom Applications Product Selection

5. Littelfuse GDT Product Road Map

6. Telecom GDT Technology Challenges

Page 2: Training Agenda - · PDF fileTelecom GDT Training Training Agenda 1. GDT Definition and Telecom Circuit Protection 2. GDT Characteristics and Device Physics 3. GDT Telecom Applications

2 Confidential and Proprietary to Littelfuse, Inc. © 2007 Littelfuse, Inc. All rights reserved.

Telecom GDT Training

Section 1 GDT Definition and Telecom Circuit Protection

GDT Definition

– A Gas Discharge Tube (GDT) is a gas discharge plasma device that provides a crowbar

current path to protect electronic components from transient threat.

Circuit Protection Concepts

– Potential safety threats that requires circuit protection

• Protect against environment threats such as Lightning, EFT Surges, and ESD

– Regulatory requirements related to circuit protection

• IEC Regulations

• UL Regulations

• Other Regulations

– Method of circuit protection

• Over voltage

• Voltage transient

– Added value of circuit protection

• Prevent disaster such as fire

• Avoid law suit and warranty issues

Page 3: Training Agenda - · PDF fileTelecom GDT Training Training Agenda 1. GDT Definition and Telecom Circuit Protection 2. GDT Characteristics and Device Physics 3. GDT Telecom Applications

3 Confidential and Proprietary to Littelfuse, Inc. © 2007 Littelfuse, Inc. All rights reserved.

Telecom GDT Training

Advantages

• Inherently bidirectional

• Low capacitance

• Ability to handle high surge currents (>20kA)

• Very low impedance following spark over

Disadvantages

• Poor initial “let through voltage” (overshoot)

• Slow response (compared to SIDACtor or PGB)

• May require series resistance to prevent follow-on current

• Trigger voltage varies

• Degrades with repetitive transients

• Fails open circuit

Gas Discharge Tubes

Working Voltage

V

t

Ignition Voltage (Overshoot)

Page 4: Training Agenda - · PDF fileTelecom GDT Training Training Agenda 1. GDT Definition and Telecom Circuit Protection 2. GDT Characteristics and Device Physics 3. GDT Telecom Applications

4 Confidential and Proprietary to Littelfuse, Inc. © 2007 Littelfuse, Inc. All rights reserved.

Circuit Protection Needs in Telecom Systems

– Thunderstorms around the world deliver 8 million lightning flashes every day. Peak current in

lightning discharges range from a few KA to many hundreds of KA. Induced currents from indirect

strikes range from 10A to 20KA.

– ESD results from the build up of electrical charge, when two non-conductive materials are brought

together then separated. The potential between a human body & an object can exceed 35,000

volts. An ESD event can occur to the telecom system or portable devices through human contact

and usage of the telecom devices.

– Inductive Load Switching is caused when an inductive load is interrupted. It occurs in

factory/industrial environments where motors and relays (inductive loads) are turned on and off.

– Short Circuit or Power Cross events can occur due to human error (such cutting a phone and power

line simultaneously during construction) or natural disaster such as hurricane, thunderstorm.

– One or a combination of the above threats can have obvious adverse effects on semiconductor/IC

devices, electro-mechanical contacts, wiring insulation, etc., to cause interruption of telecom

equipment operation, telephone service, and even fire.

GDT Definition and Telecom Circuit Protection

Page 5: Training Agenda - · PDF fileTelecom GDT Training Training Agenda 1. GDT Definition and Telecom Circuit Protection 2. GDT Characteristics and Device Physics 3. GDT Telecom Applications

5 Confidential and Proprietary to Littelfuse, Inc. © 2007 Littelfuse, Inc. All rights reserved.

GDT Definition and Telecom Circuit Protection

GDT Technology for Telecom Overvoltage Circuit Protection

Telecom equipment should be protected from overvoltage conditions using GDTs, MOVs, or

silicon devices such as SIDACtors or TVS diodes.

Gas Discharge Tubes / Surge Arresters are mostly used for Primary Protection against transients

caused by lightning.

Secondary Protection applications traditionally have used Silicon solutions but due to the

increased bandwidth now required by telephone lines the GDT has the benefit of having

significantly lower capacitance levels and are now competing with Silicon solutions due to their

relatively high capacitance.

Page 6: Training Agenda - · PDF fileTelecom GDT Training Training Agenda 1. GDT Definition and Telecom Circuit Protection 2. GDT Characteristics and Device Physics 3. GDT Telecom Applications

6 Confidential and Proprietary to Littelfuse, Inc. © 2007 Littelfuse, Inc. All rights reserved.

Telecom GDT Training

Section 2 GDT Characteristics and Device Physics

• Basic GDT Characteristics

– Electrical Characteristics

• V-I curve characteristics

• Trigger voltage

• Clamping voltage

• Response time

• Leakage current

• GDT Construction and how it affects the related GDT characteristics

– GDT structure vs. electrical characteristics

– GDT structure vs. maximum ratings

– GDT de-rating

Page 7: Training Agenda - · PDF fileTelecom GDT Training Training Agenda 1. GDT Definition and Telecom Circuit Protection 2. GDT Characteristics and Device Physics 3. GDT Telecom Applications

7 Confidential and Proprietary to Littelfuse, Inc. © 2007 Littelfuse, Inc. All rights reserved.

GDT Characteristics and Device Physics

Electrical GDT Characteristics

VH (holdover voltage) is the key

parameter. With the exception of 75V

and 90V devices that have a holdover

voltage of 50V, all other devices have a

holdover voltage of 135V which will not

cause latch up for the telecom system.

VSDC (DC breakover voltage) is

measured at a slow rate of rise, usually

100V/sec. This is to make sure that the

lower DC breakover voltage is above

the system voltage.

VS (dynamic breakover voltage)

determines the level of protection

clamping voltage.

Page 8: Training Agenda - · PDF fileTelecom GDT Training Training Agenda 1. GDT Definition and Telecom Circuit Protection 2. GDT Characteristics and Device Physics 3. GDT Telecom Applications

8 Confidential and Proprietary to Littelfuse, Inc. © 2007 Littelfuse, Inc. All rights reserved.

GDT Characteristics and Device Physics

GDT Construction

The gas plasma arrester operates as a

voltage dependent switch. When the spark

over voltage applies across the device

greater than its breakdown voltage, an arc

discharge takes place within the tube.

A gas plasma device can typically handle

5kA to 20kA current.

The performance of the GDT can be

determined by the following factors:

- Electrode material, shape and surface

finish.

- Electrode coatings/activation, electron work

function, and Electrode spacing.

- Gas volume and pressure, temperature

Type of gas, and ionization energy of the

gas.

Page 9: Training Agenda - · PDF fileTelecom GDT Training Training Agenda 1. GDT Definition and Telecom Circuit Protection 2. GDT Characteristics and Device Physics 3. GDT Telecom Applications

9 Confidential and Proprietary to Littelfuse, Inc. © 2007 Littelfuse, Inc. All rights reserved.

Telecom GDT Training

Section 3 GDT Telecom Applications Protection Examples

•Exchange Equipment

•Main Distribution Frame

•Subscriber Terminal

•Telephones

•Fax Machines

•Modems

•Base Stations for Cell Phones

•Multiplexers

•LAN Network Terminals

•Amplifiers

•ADSL/VDSL/HDSL Equipment

Page 10: Training Agenda - · PDF fileTelecom GDT Training Training Agenda 1. GDT Definition and Telecom Circuit Protection 2. GDT Characteristics and Device Physics 3. GDT Telecom Applications

10 Confidential and Proprietary to Littelfuse, Inc. © 2007 Littelfuse, Inc. All rights reserved.

GDT Telecom Applications Protection Examples

All outside plant protectors perform a Primary Protection function, meaning they act as the first

line of defense. The Gas Plasma device, because of it’s high energy capability (up to 20KA),

is ideal for these applications. Typically, 5KA would be the lowest rating for a Primary

Protector used in an outside plant application.

Telecom 3 Point Protection Solution (typically employed in outside plant protectors)

Page 11: Training Agenda - · PDF fileTelecom GDT Training Training Agenda 1. GDT Definition and Telecom Circuit Protection 2. GDT Characteristics and Device Physics 3. GDT Telecom Applications

11 Confidential and Proprietary to Littelfuse, Inc. © 2007 Littelfuse, Inc. All rights reserved.

GDT Telecom Applications Protection Examples

Telecom 3 Point Protection Solution (typically employed in outside plant protectors)

Three terminal Gas Plasma devices are constructed using a common gas

chamber, so in differential mode (a transient appearing on both Tip and Ring) the

resulting differential transient is smaller.

Two terminal tubes are often easier, from a mechanical standpoint, to incorporate

in module designs.

3 Terminal GDT 2 x 2 Terminal GDT

Page 12: Training Agenda - · PDF fileTelecom GDT Training Training Agenda 1. GDT Definition and Telecom Circuit Protection 2. GDT Characteristics and Device Physics 3. GDT Telecom Applications

12 Confidential and Proprietary to Littelfuse, Inc. © 2007 Littelfuse, Inc. All rights reserved.

GDT Telecom Applications Protection Examples

MDF Protection Modules

MDF modules perform some level of Primary Protection, but often incorporate

secondary level features as well. Such devices are are of Hybrid construction

incorporating more than one technology.

Page 13: Training Agenda - · PDF fileTelecom GDT Training Training Agenda 1. GDT Definition and Telecom Circuit Protection 2. GDT Characteristics and Device Physics 3. GDT Telecom Applications

13 Confidential and Proprietary to Littelfuse, Inc. © 2007 Littelfuse, Inc. All rights reserved.

GDT Telecom Applications Protection Examples

Telecom 5 Point Protection Solution (Hybrid design commonly deployed in MDF modules)

Depending on geography, the level of primary protection provided in the MDF varies. In

certain regions of the world the effects of lightning can be more severe. In these cases,

the MDF module will need a surge rating of several thousand Amperes (KA); the solution

here is to use a Gas Plasma device. A typical rating in this application is 5KA.

Page 14: Training Agenda - · PDF fileTelecom GDT Training Training Agenda 1. GDT Definition and Telecom Circuit Protection 2. GDT Characteristics and Device Physics 3. GDT Telecom Applications

14 Confidential and Proprietary to Littelfuse, Inc. © 2007 Littelfuse, Inc. All rights reserved.

GDT Telecom Applications Protection Examples

3 Terminal Device (to provide protection against isolation breakdown on transformer)

In order to transfer high speed data over distance and without loss or corruption, the

protector has a exhibit low ‘insertion loss’ values (normally measured in dB). To some

extent, the capacitance value has a direct relationship with insertion loss: higher

capacitance = higher insertion loss.

Littelfuse “broadband optimized” protectors offer very low insertion loss, even up to 1.8Ghz,

making them virtually transparent to the protected system.

Page 15: Training Agenda - · PDF fileTelecom GDT Training Training Agenda 1. GDT Definition and Telecom Circuit Protection 2. GDT Characteristics and Device Physics 3. GDT Telecom Applications

15 Confidential and Proprietary to Littelfuse, Inc. © 2007 Littelfuse, Inc. All rights reserved.

GDT Telecom Applications Protection Examples

Global Lab Capabilities • Qualification of all LF products

• UL-Approved Customer Testing in ISO 17025 Lab (Des Plaines)

– High power (AC/DC up to 1KV/50KA) UL approvals available in DP

– Telcordia approvals in DP planned (2008)

• Verification of Telcordia, ITU, IEC, FCC, and other industry, regulatory, and safety standards

– Verification to various OC and OV standards

• Insure application meets standards before submitting for approval

• Customer Application testing

– Assistance with design-in and performance verification

• Help with selection of appropriate technology and rating

– Application troubleshooting

• Assistance insuring proper OV/OC and primary/secondary protection coordination

– Competitive evaluations

• Competitive or technology performance comparisons

– Reliability & Tin Whisker data/testing

Page 16: Training Agenda - · PDF fileTelecom GDT Training Training Agenda 1. GDT Definition and Telecom Circuit Protection 2. GDT Characteristics and Device Physics 3. GDT Telecom Applications

16 Confidential and Proprietary to Littelfuse, Inc. © 2007 Littelfuse, Inc. All rights reserved.

Telecom GDT Training

Section 4 GDT Telecom Applications Product Selection

GDT Product Selection

– Select power rating: 5A/5KA, 10A/10KA or 20A/20KA

– Select package outline: 2 Pole, 3 Pole, Axial, Radial or SM

– Choose a device with a minimum DC Breakdown higher than the maximum system voltage

– Select the corresponding device voltage type

Page 17: Training Agenda - · PDF fileTelecom GDT Training Training Agenda 1. GDT Definition and Telecom Circuit Protection 2. GDT Characteristics and Device Physics 3. GDT Telecom Applications

17 Confidential and Proprietary to Littelfuse, Inc. © 2007 Littelfuse, Inc. All rights reserved.

GDT Telecom Applications Product Selection

Overvoltage Protection Comparison

Technology

GDT

GDTs

MOV

TVS

Response Time

Fastest

Slowest

Slower

response time

Fast

Capacitance

Low

As low as 1pF

High

Higher

Current

surge rating

High

As high as 500A

for 200 impulses

High

Low

Electrical

Characteristic

Stable

Degrade with time

Fatigue after

multiple

pulses

Stable

Application

Principle Overvoltage

in telecom, datacom

circuit

Telecom

application

Useful in AC

applications

Secondary Protectors

Page 18: Training Agenda - · PDF fileTelecom GDT Training Training Agenda 1. GDT Definition and Telecom Circuit Protection 2. GDT Characteristics and Device Physics 3. GDT Telecom Applications

18 Confidential and Proprietary to Littelfuse, Inc. © 2007 Littelfuse, Inc. All rights reserved.

GDT Telecom Applications Product Selection

Characteristics of Transient Voltage Suppressor Technology

Page 19: Training Agenda - · PDF fileTelecom GDT Training Training Agenda 1. GDT Definition and Telecom Circuit Protection 2. GDT Characteristics and Device Physics 3. GDT Telecom Applications

19 Confidential and Proprietary to Littelfuse, Inc. © 2007 Littelfuse, Inc. All rights reserved.

GDT Telecom Applications Product Selection

GDT Selection

Page 20: Training Agenda - · PDF fileTelecom GDT Training Training Agenda 1. GDT Definition and Telecom Circuit Protection 2. GDT Characteristics and Device Physics 3. GDT Telecom Applications

20 Confidential and Proprietary to Littelfuse, Inc. © 2007 Littelfuse, Inc. All rights reserved.

Telecom GDT Training

Section 5 Littelfuse GDT Product Road Map

Page 21: Training Agenda - · PDF fileTelecom GDT Training Training Agenda 1. GDT Definition and Telecom Circuit Protection 2. GDT Characteristics and Device Physics 3. GDT Telecom Applications

21 Confidential and Proprietary to Littelfuse, Inc. © 2007 Littelfuse, Inc. All rights reserved.

Telecom GDT Training

Section 6 Telecom GDT Technology Challenges

– Higher Surge Rating and Smaller Packaging

– Multiple Elements in One Package

– GDT Technology Combined with Other Technologies in Same Package

– Improved De-rating Characteristics