Gas Discharge Tubes (GDT) Training Material  Construction and Characteristics of GDTs  Performance Ratings  Selection of GDT for Application  Applications when NOT to use GDTs  Comparison of Protective Devices Page 1

Gas Discharge Tubes Page 2 A bolt of lightning flashes through the sky and hits the ground somewhere around the world about 100 times every second. That’s 8 million lightning strikes in a single day! Scientific America- Nov 2014 – Global Warming: New findings suggest lightning strikes may increase by 12% for every degree (°C) of warming … That comes to a 50% increase ( in number of lighting strikes ) by the end of the century Gas discharge tubes (GDTs) are ideal for lightning surge protection of electronic equipment, as GDTs can dissipate large amounts of energy in small size components Why are Gas Discharge Tubes needed?

Electrode Solder Ceramic Tube Construction of GDTs Gas Discharge Tubes Page 3 Gas discharge tubes by nature of their construction can handle very large amounts of current, are bidirectional. They have very high impedance and low capacitance, resulting in very little current leakage or signal loss. So the GDT is ‘virtually invisible’ to the protect circuit. GDTs are normally used as primary protection devices, in conjunction with other kinds of protect devices (with faster response speed) as secondary protection. When a surge voltage reaches the GDT spark-over voltage, the GDT will switch into virtual short, divert the surge current through the GDT to ground and removing the voltage surge from damaging the equipment. Therefore, GDTs provide excellent protection during the time period that they are active.

The Townsend discharge is a gas ionization process where free electrons, accelerated by a sufficiently strong electric field, give rise to electrical conduction through a gas by avalanche multiplication, called an Townsend Avalanche. An electron avalanche is a process in which a number of free electrons in a transmission medium (gas) are subjected to strong acceleration by an electric field and subsequently collide with other atoms of the medium, thereby ionizing them (impact ionization). This releases additional electrons which accelerate and collide with further atoms, releasing more electrons—a chain reaction. In a gas, this causes the affected region to become an electrically conductive plasma. The avalanche effect was discovered by John Sealy Townsend in his work between 1897 and 1901, and is also known as the Townsend discharge. Visualization of a Townsend Avalanche* Characteristics of GDTs Gas Discharge Tubes Page 4

Gas Discharge Tubes Page 5 Voltage Current Standoff Resistance Gas Discharge Tube

Page 6 Gas Discharge Tubes Typical GDT specification sheet The following is a review of the GDT specifications 

DC Breakdown & Spark-over Voltage  SELECTION GUIDE: With the same DC Breakdown Voltage, the lower the Impulse Spark-Over Voltage, the faster the response speed and the better protection Part Number DC Breakdown Voltage (100V/s) Breakdown Voltage Tolerance (V) Impulse Spark-Over Voltage (1KV/μS) NGTA1812N401TR1F400V340~550≤750V NGTC1812N401TR1F400V360~560≤950V Page 7 Better protection; lower impulse voltage = faster response Slower response The curves (left) show the typical DC breakdown voltage (100V/S) and Impulse Spark-over Voltage (1000V/uS) of NGTA series GDT Gas Discharge Tubes Selected based upon operating voltage level (VDC) The value of Impulse Spark-over Voltage reflects the Gas Discharge Tube response speed

The arc voltage is developed across the GDT during its “virtual short circuit” condition. This parameter defines the power dissipation of the GDT during its protection mode.  GUIDE: A low arc voltage is desirable to keep power dissipation at a minimum, which in turn increases the life expectancy of the gas discharge tube. Higher power dissipation (higher operation temperature) will act to reduce the lifetime of the gas discharge tube. Arc voltage under AC voltage condition Page 8 Voltage Current Gas Discharge Tubes – Arc Voltage The voltage developed across the GDT component when it is operating is called the “Arc Voltage“ ( V a in above example ) The voltage developed across the GDT component when it is operating is called the “Arc Voltage“ ( V a in above example ) Low Arc Voltage of GDT construction makes the GDT ideal protection against lightning (high-energy) and AC line overvoltage conditions

Solution BSolution A 48VDC solution Examples: Two solutions (A & B) for 48VDC power port, solution A (above left) uses a special 5-element, 6-terminal GDT. The Arc voltage is higher than 48VDC, so it is safe choice. Solution B (above right) use a lower voltage single GDT (PN: NGTF2016M091TR5F) in series with a MOV, because the arc voltage of NGTF2016M091TR5F is about which is lower than the 48VDC system voltage, so it needs to be used in series with a MOV which will claim above 48VDC Gas Discharge Tubes – Arc Voltage While low Arc Voltage is desired to minimize power dissipation, the Arc voltage of the GDT in DC circuits should be above the operating voltage level to assure turn off of the GDT. When GDT is used to protect 48VDC power port, the arc voltage of the gas discharge tube should be selected to be higher than the operating voltage, as shown in Solution ‘A’ below, or used in series with a MOV (such as NIC NVR series) as shown in Solution ‘B’ below Page 9

NGTA1812N301TR1F NGTA1812N401TR1F NGTF2016M351TR5F NGTF2016M801TR3F NGTF2016M102TR3F NGTF2016M122TR3F NGTM2332M351TR20F NGTM2332M471TR20F NGTM2332M601TR20F NGTM2332M801TR20F NGTM2332M152TR10F NGTM2332M362TR10F NGTD3020M231TR5F NGTD3020M102TR5F 15V DC12V AC24V DC12V AC24V DC12V AC24V DC12V AC24V NIC has developed Higher Arc Voltage GDTs, which can be applied in higher voltage DC/AC applications Format Part Number Application Arc Voltage at 1A Gas Discharge Tubes – Arc Voltage Page 10

NGTA / NGTC (4.5x3.2x2.7) NGTD (7.6x5x5) Custom (24.1x8.3x9.2) Custom (16.5x8.3x9.5 & 19.9x8.3x9.3) NGTF (4.2x5x5) NGTM (6x8.3x8.3) High Surge Current rating is one of the main characteristic of GDTs. NIC can provide surge current rating: 1KA ~ 8/20uS in single and multiple element construction GDT suggested as the primary circuit protection, due to its high surge current rating performance. Gas Discharge Tubes - Surge Current 1KA / 2KA 5KA 20KA Single Element Construction Multiple Element Construction (2, 4, 5) Page 11

SeriesTypical Capacitance Value NGTA0.26pF NGTC0.26pF NGTD0.57pF NGTF0.48pF NGTM0.98pF Another characteristic of GDT is capacitance value, which is very important for data signal transfer, especially for high speed - frequency (lower capacitance = less signal loss). NIC provides GDTs with very low capacitance as shown below. Typical Capacitance Gas Discharge Tubes  SELECTION GUIDE: To protect high speed applications, the protection device must have low capacitance values Page 12 Silicon Avalanche Suppressors, MOVs & Transzorbs can have >100pF capacitance value

Parameters - Characteristics of GDTs Gas Discharge Tubes Lower is better Higher is better Selection based upon operating voltage Guidance based upon application VAC or VDC Page 13

GDT Selection GDT selection When used to protect power port, Arc Voltage must be higher than the peak value of the supply voltage DC Breakdown Voltage Must be higher than the peak work voltage of the protective circuit It must be higher than the highest surge current of the protected circuit Impulse Spark-over Voltage Must be lower than the highest voltage the protected circuit can allow Arc Voltage Surge Current Rating Gas Discharge Tubes Page 14

GDTs are suggested for use in primary protection, but not suggested for use in secondary or ESD protection Primary Protection: GDT Example: Tip & Ring xDSL protection solution Low response speed High residual voltage High surge current rating Good for large surge current protection Use in primary protection Not suggested for fine protection Not used in secondary or ESD protection Gas Discharge Tubes Secondary or ESD Protection TVS Page 15

GDT Arc voltage 12VDC solution L +12V 0V Gas Discharge Tubes When GDT is used in power port, need to be cautious in selection of GDT. Must ensure the GDT can shut off after surge wave has passed. The arc voltage of the GDT should be selected higher than the circuit voltage, or use the GDT in series with a MOV. When GDT is used in power port, need to be cautious in selection of GDT. Must ensure the GDT can shut off after surge wave has passed. The arc voltage of the GDT should be selected higher than the circuit voltage, or use the GDT in series with a MOV. Secondary Protection TVS Protected Circuit Page 16

GDT – Gas Discharge Tube TSS - Thyristor Surge Suppressors TVS - Transient Voltage Suppressor MOV - Metal Oxide Varistor Operating Principle Gas discharge Avalanche effect of PN junction Avalanche effect of PN junction Nonlinear voltage characteristic Protection Mode Switch Mode Clamp Mode Response speed SlowFastVery fastMedium Ability of withstand high voltage HighMediumLowMedium--High Leakage Very low<5uA<5-10uA<20-30uA Capacitance Very low, normally lower than 1pF Mid (be related to lightning level) Large (be relate to the size and lighting level) Failure Mode OpenShort Device Item Comparison of Over-Voltage Protective Devices Page 17

Switch Mode Clamp Mode TVS - Transient Voltage Suppressor MOV - Metal Oxide Varistor TSS - Thyristor Surge Suppressor GDT – Gas Discharge Tube Comparison of Over-Voltage Protective Devices Page 18

Comparison of Over-Voltage Protective Devices GDT – Gas Discharge Tube TSS - Thyristor Surge Suppressors TVS - Transient Voltage Suppressor MOV - Metal Oxide Varistor Advantage High Surge Current Rating, Low Capacitance, Low Leakage Low Residual Voltage, Fast Response Speed, High Accuracy of Voltage Low Residual Voltage, Fast Response Speed, High Accuracy of Voltage High Accuracy of Voltage, Low cost Disadvantage High Residual Voltage, Slower Response Speed Limited Voltage Range, Can Not Be Used In Power supply Port Low Surge Current Rating, Unit cost increases with Surge Current Rating Increase High Capacitance, Easy Degenerate, Large Leakage Typical Usage Applications Mainly used to primary protection of signal ports with high flow capability or low voltage power supply ports Mainly used primary or secondary protection of signal ports, Normally not used in power supply ports Mainly used for fine protection, such as secondary, third level protection and ESD protection Mainly used in power supply ports, normally not used in signal ports due to its’ high capacitance. Page 19

NGTA / NGTC (4.5x3.2x2.7) NGTD (7.6x5x5) NGTF (4.2x5x5) NGTM (6x8.3x8.3) NIC SMT Gas Discharge Tubes SMT Format: Single Element Construction & 2-Element Construction SeriesSize Breakdown Voltage Current Impulse Spark-over Voltage NGTA V  400V 1KA 650V  750V NGTC V  600V 2KA 700V  1200V NGTD V  1000V 2KA & 5KA 700V  1800V NGTF V  1200V 3KA & 5KA 650V  2000V NGTM V  3600V5KA  20KA600V  5000V Featuring: Ultra High Current, Low Capacitance & Low Insertion Loss QVGQ2.E / E Isolated Loop Circuit Protectors – Component, Transient-voltage surge suppressors, gas tube Page 20

NIC SMT Gas Discharge Tubes Page 21 Gas Discharge Tubes Applications  Power Supply Voltage Protection  ADSL, xDSL Applications  General Telecommunication Equipment  CATV & Satellite Applications  Communications Equipment  Smart Metering, Green Power  Data Transmission Line - Port Protection:  RS485  RS232  xDSL  Ethernet

Page 22 NIC Circuit Protection Products NFVC Series Chip Fuse Over-current Protection NPX Series X2 Capacitor Interference Suppression NVR Series Metal Oxide Varistor (MOV) Over-voltage protection NGT_ Series Gas Discharge Tubes Over-voltage Protection NIC Circuit Protection Products → NGT_ - SMT Gas Discharge Tubes → NVR – MOV High Voltage Varistors → NPX – X2 Safety Capacitors → NFVC – 125V / 250VAC Chip Fuses NIC Circuit Protection Products → NGT_ - SMT Gas Discharge Tubes → NVR – MOV High Voltage Varistors → NPX – X2 Safety Capacitors → NFVC – 125V / 250VAC Chip Fuses

Additional Information Needed? Need Samples ? Additional Information Needed? Need Samples ? NIC Components offers unique performance passive components that provide advantages to design engineers to create high performance end products in smaller and lower total cost formats Surface Mount SMT formats (high speed auto placement) Pb-Free Reflow Compatible (high temperature reflow) Performance advantages over competing technologies Technical Support: Sales Support: Technical Support: Sales Support: North America Engineering Support SE Asia Engineering Support European Engineering Support Page 23