Varistor Products Overview April 7, 2010 CIRCUIT PROTECTION SOLUTIONS 1 Version01_100407 Agenda 1. MOV (Metal Oxide Varistor) fundamentals - Mechanism of operation - Electrical Characteristics 2. MOV / MLV (Multi-Layer Varistor) types and applications 2 Version01_100407 Transient Surges are Everywhere COMPUTERS • ESD • EFT • SURGES TELECOM EQUIPMENT AUTOMOTIVE • LOAD DUMP • INDUCTIVE LOADS • TRANSIENT BURSTS Littelfuse WHITE GOODS INDUSTRIAL PANELS PORTABLE ELECTRONIC EQUIPMENT • ESD HOME ENTERTAINMENT 3 Version01_100407 MOV Definition An MOV, or Metal Oxide Varistor, is a voltage suppression device that clamps a transient in an electrical circuit. It is also called a Varistor , or variable resistor, because its resistance changes with applied voltage. Sometimes they are referred to as a VDR, or Voltage Dependant Resistor, by some manufacturers. An MOV is a voltage dependent device which has an electrical behavior similar to back to back zener diodes. When exposed to high voltage transients, the MOV’s resistance changes from a near open circuit to a very low value, thus clamping the transient voltage to a safe level. The potentially destructive energy of the incoming transient pulse is absorbed by the Varistor, thereby protecting vulnerable circuit components. 4 Version01_100407 Terms Voltage Transients Surges Voltage Spikes Overvoltage events (short duration) All mean the same thing. 5 Version01_100407 Lightning Transients 70 Volts at 1 mile 10,000 Volts at 500 feet Underground wires Electromagnetic coupling into overhead and buried wires 6 Version01_100407 ESD Electro-Static Discharge Walking across a carpet: 35,000 Volts @ RH = 20% 500 Volts @ RH = 65% Walking across a vinyl floor: 12,000 Volts @ RH = 20% 250 Volts @ RH = 65% 7 Version01_100407 Clamping action Transient on Line Energy Dissipated Vline Vline Clamp Voltage Line MOV Ground 8 Version01_100407 MOV Electrical Parameters Voltage Rating, Energy Peak Current Varistor Voltage Continuous at 1mA VDC VAC VDC Joules Amps 130 170 100 10000 operating voltage 185 min 225 max Varistor voltage 1 pulse energy rating Clamp Voltage Capacitance 8x20µS (typical) Vpeak Amps pF 340 100 1900 clamp voltage at specific current typical capacitance 1 pulse current rating After only 1 hit of these two max limits, the MOV will need to be replaced. 9 Version01_100407 V-I curve characteristics 1. Leakage/Low current region Acts as a large resistor until reaching the clamping region. 2. Clamping Region Acts as a conductor in this region. Conducts large amount of current for a small increase in voltage 3. High Current/Upturn region Lower lifetime when used in this region 10 Version01_100407 V-I curve characteristics 1. Leakage/Low current region Acts as a large resistor until reaching the clamping region. 2. Clamping Region Acts as a conductor in this region. Conducts large amount of current for a small increase in voltage 3. High Current/Upturn region Lower lifetime when used in this region 11 Version01_100407 V-I curve characteristics 1. Leakage/Low current region Acts as a large resistor until reaching the clamping region. 2. Clamping Region Acts as a conductor in this region. Conducts large amount of current for a small increase in voltage. 3. High Current/Upturn region Limited lifetime when used in this region. 12 Version01_100407 V-I curve characteristics For the same MOV voltage rating: • Small diameter parts have a higher clamp voltage. • Large diameter parts have higher current capability 13 Version01_100407 Continuous Power Dissipation MOVs are only used for transient suppression, and not continuous voltage regulation. Their power rating for continuous current is very low. Their power rating for brief millisecond transients is very high. Leakage Current Leakage current will increase as the temperature rises. MOV voltage MOV Characteristics MOV current 14 Version01_100407 Pulse Rating Curve • Guaranteed lifetime, meaning less than a 10% shift in Varistor Voltage. How many events before replacement • High current events will rapidly decrease lifetime. • Wide transients such as 100mS should be avoided. 15 Version01_100407 MOV selection 1. Continuous Voltage Rating, RMS or DC, should be >110% of the maximum expected voltage. 2. Device size depends on the transient energy or current expected or on the required clamping voltage. 3. Energy and Peak Current ratings are a measure of capability. 4. Max Clamping voltage is a reference point on the V-I curve and is a measure of the protection level. 5. Varistor voltage can be used for Incoming Inspection and internal manufacturing test purposes. 16 Version01_100407 MOV Selection Table Voltage range Energy Normal use Series 130 - 1000 11 - 360 AC Power Lines PCB through-hole mounting LA CIII UltraMOV - TMOV 130 - 275 11 - 40 Low Energy Surface Mount CH, SM7 130 - 750 270 - 1050 High Energy Chassis and Board Mount DA, DB HA, HB, DHB 130 - 880 450 - 3200 Primary Power Line Heavy Industrial, Chassis Mount BA 1100 - 2800 3800 - 10000 Motors, Switch Gear Heavy Industrial, Chassis Mount BB 5.5 - 460 .1 - 52 Low Voltage PCB through-hole mounting ZA 17 Version01_100407 MOV Radial Portfolio 5 Series of Leaded MOVs LA Lowest energy 130V - 1000V UltraMOV Medium energy 130V - 625V C-III Highest energy 130V - 320V ZA Low energy Low voltage TMOV Medium Energy 115 – 750V Thermally protected 5V – 460V 18 Version01_100407 MOV Radial Sizes Disc Diameter (mm) LA ……………..…… 5 , 7, 10, 14, 20 Diameter UltraMOV ……….…. 7, 10, 14, 20, 25 C III…………………………………...…14, 20 ZA ……..………….…. 5, 7, 10, 14, 20 TMOV……………..................………14, 20, 25, 34 19 Version01_100407 MOV Radial Ratings Peak Current Series 7mm 10mm 14mm 20mm 25mm LA 1.2kA 2.5kA 4.5kA 6.5kA C III 6.0kA 9.0kA UltraMOV 1.75kA 3.5kA 6.0kA 10.0kA 22kA ZA 100-1.2kA 250-2.5kA 1- 4.5kA 2- 6.5kA TMOV 6kA 10kA 20kA 34mm 40kA Energy Series 7mm LA 11-35 C III UltraMOV 12.5-48 ZA .4-10 TMOV 10mm 14mm 20-70 38-220 70-360 45-130 90-220 50-200 100-400 230-890 3.5-35 7-52 35-6000 52-480 170-670 235-1050 25-100 .8-18 20mm 25mm 34mm 20 Version01_100407 TMOV Thermally Protected MOV What is the TMOVTM Varistor? • • • The TMOV Varistor is a Metal Oxide Varistor with an integrated thermally activated element. The device will automatically and permanently opencircuit when overheating occurs due to certain sustained over-voltages thereby providing additional thermal safety for the circuit. The MOV will become permanently disconnected. The integrated thermal element means it will not flame, fragment or scorch when subjected to an abnormal sustained over-voltage condition defined in UL Standard 1449. 21 Version01_100407 TMOV and iTMOV TMOV iTMOV Thermal Fuse Monitor Lead MOV Line Line Neutral Diode To Protected Circuit TMOV Fuse LED Normally On iTMOV R To Protected Circuit Fuse Neutral 22 Version01_100407 TMOVTM Varistor Typical TMOV body temperature during UL1449 limited current abnormal overvoltage test 23 Version01_100407 Application solutions Typical installation for plug-in or permanently wired equipment Equipment Fuse AC Power Input Washing Machine Microwave TV Set Top Box Radio PC etc 24 Version01_100407 Application solutions Typical MOV placement at power supply input Line Neutral Ground 25 Version01_100407 Application solutions MOV placement with line-to-ground isolation Line Neutral GDT in series with MOV Ground 26 Version01_100407 Set Top Box Power Supply Fuse provides overcurrent protection. Primary protection provided by MOVs. Further protection can be provided by including additional MOVs on the secondary side. 27 Version01_100407 MOV Industrial Series Description Leaded and Packaged Devices for Hi Energy applications. Several mounting variations are available. Technology is similar to the Radial leaded devices. All series are in the range 130VAC and up. 28 Version01_100407 Industrial Series Summary Series CA HA HB/DHB DA/DB BA BB Size 60mm 32mm 40mm 34mm 40mm 60mm 60mm Voltage 250 - 2800VAC 130 - 750VAC 130 - 750VAC 130 - 750VAC 130 - 750VAC 130 - 880VAC 1100 - 2800VAC Package Bare disc Bolt or thru-slot board mount Bolt or thru-slot board mount Box, upright or flat. Box, upright Box, upright 29 Version01_100407 Industrial Series HA Series Solderable contacts Voltage range Size (Dia) 130VAC - 750VAC 32 / 40mm Part Number : V321HA40 VAC where 1 = x10 i.e. 321 = 320VAC Disc Diameter A=Bolt on terminal C= PCB mount 30 Version01_100407 Industrial Series HB Series Solderable contacts Voltage range Size 130VAC - 750VAC 34mm square Part Number : V321HB34 VAC where 1 = x10 i.e. 321 = 320VAC Disc Diameter 31 Version01_100407 Industrial Series DA/DB Series Screw contacts Voltage range Size (Dia) 130VAC - 750VAC 40mm Part Number : V321DA40 Vrms where 1 = x10 i.e. 321 = 320VAC Disc Diameter Different box style, A or B 32 Version01_100407 Industrial Series BA/BB Series Screw contacts Style BA BB Voltage range Size (Dia) 130VAC - 750VAC 1100VAC – 2800VAC 60mm 60mm Part Number : V321BA60 VAC where 1 = x10 2 = x100 i.e. 321 = 320VAC Disc Diameter Different box style A and B 33 Version01_100407 Test Levels All standards attempt to apply levels of severity to the described waveforms, example: ANSI 62/UL1449 Waveform A B 0.5ms-150kHz 6kV 200A 6kV 500A 1.2 / 50us 8 / 20us 6kV 3kA C 10kV 10kA 34 Version01_100407 Industrial Applications Industrial Controls Motor Drives Generator Protection Industrial Distribution Panels Electric Locomotives Thyristor Power Switching Protection Din Rail Circuit Breaker Box Protection Base station protection 35 Version01_100407 Applications Motor Drive Controller Electric Motor Drive Power Input To ensure Input Power is “clean” May include to protect against transients from the Motor 36 Version01_100407 Surface Mount MOVs 7mm and 20mm disc sizes inside. 37 Version01_100407 Multilayer Varistor Nicknamed ML or MLV Leadless, Surface Mount Chip Form Combine Surge, ESD, and Filtering Functions Rugged, Robust, Reliable Four distinct versions: ML - supports the broadest application range MHS - low capacitance, high speed ML MLE - intended for ESD while providing filter functions AUML - automotive load dump transient protection 38 Version01_100407 Multilayer Varistors What is an MLV? MLV’s are voltage dependant, non-linear devices used in overvoltage transient suppression. MLV’s are fabricated by wet stack printing layers of Zinc-Oxide (ZnO) and metal inner electrodes, sintering, terminating, glassing & finally plating. MLV’s are available in sizes 0402 up to 2220 MLV’s are available in voltages 3.5Vdc up to 120Vdc 39 Version01_100407 Multilayer Varistor What does an MLV look like inside? Fired Zinc Oxide Black Ceramic End Termination Standard finish is Tin (Sn) plated over Nickel (Ni) plated over Silver (Ag) Glass is porous and is put on before Ni & Sn Termination, Metal Inner Electrodes Platinum (Pt) or Silver-Palladium (AgPd) 40 Version01_100407 Multilayer Varistors (MLV) What does an MLV look like inside? continued Metal Inner Electrodes End Termination (Side view) (End view) 41 Version01_100407 MLV Electrical Parameters Voltage Rating, Energy Peak Current Varistor Voltage Continuous at 1mA VDC VAC VDC Joules Amps 14 18 0.4 150 operating voltage 22 min 28 max Varistor voltage 1 pulse energy rating Clamp Voltage Capacitance 8x20µS (typical) Vpeak Amps pF 40 10 1100 clamp voltage at specific current typical capacitance 1 pulse current rating After only 1 hit of these two max limits, the MOV will need to be replaced. 42 Version01_100407 V-I curve characteristics For the same MOV voltage rating: • Smaller parts have a higher clamp voltage at a higher currents. • Larger parts have a higher energy capability. 43 Version01_100407 Multilayer Products Series Voltage Size MLA 3.5v – 30VDC 30v – 120VDC 0603 - 1210 1206 - 1210 MLE 18VDC 0603 - 0805 - 1206 MHS 9V – 42 VDC 0402 - 0603 MLN 5.5v – 18VDC 1206 4X array AUMLA 18VDC 1206 -1210 - 1812 - 2220 44 Version01_100407 Multilayer Series Five Sizes 0805 0603 0402 1mm 1206 1.6mm 2.0mm 1210 3.0mm 3.2mm .5mm .8mm 1.3mm 1.5mm 2.5mm 45 Version01_100407 SurgeArrayTM MLN A network of four independent multilayer varistors. in a single 1206 surface mount package. 5.5, 9, 14, 18 VDC available. The inherent capacitance provides filtering capability to eliminate the need for an additional capacitor. Reduces board space and assembly placement cost while increasing assembly capacity and system reliability. 46 Version01_100407 Multilayers for Automotive applications AUMLA Used to handle load dump requirements Four sizes 1206 1.6mm 1812 1210 3.2mm 3.2mm 2220 5.7mm 4.5mm 2.5mm 3.2mm 5.0mm 47 Version01_100407 MLA Performance ESD Test Voltage Peak Clamp Voltage 100 8kV 4kV V18MLA0805 2kV 1kV 0.5kV V5.5MLA0805 10 0.1 1.0 10.0 100.0 Peak Impulse Current 48 Version01_100407 Transient Suppression Performance Voltage vs Time curves for contact discharge ESD 8kV 6kV 4kV 2kV 1kV 500V V18MLA0805 Voltage 80 60 40 20 0 0 10 20 30 40 Nanoseconds 50 60 70 80 49 Version01_100407 CH Series Original surface mount Varistor series using Disc Press Technology Voltage range 14VAC - 275VAC Large 5x8mm package Advantage over ML – Higher voltages to 275VAC – Higher energy capability – Higher peak current capability Standard color is dark blue. Multilayers are black. 50 Version01_100407