ML Varistor Series. Surface Mount Varistors. Features. Size Metric EIA

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1 The ML Series family of Transient Voltage Surge Suppression devices is based on the Littelfuse Multilayer fabrication technology. These components are designed to suppress a variety of transient events, including those specified in IEC -4-2 or other standards used for Electromagnetic Compliance (EMC). The ML Series is typically applied to protect integrated circuits and other components at the circuit board level. The wide operating voltage and energy range make the ML Series suitable for numerous applications on power supply, control and signal lines. The ML Series is manufactured from semiconducting ceramics, and is supplied in a leadless, surface mount package. The ML Series is compatible with modern reflow and wave soldering procedures. It can operate over a wider temperature range than zener diodes, and has a much smaller footprint than plastic-housed components. Littelfuse Inc. manufactures other Multilayer Series products. See the MLE Series data sheet for ESD applications, MHS Series data sheet for high-speed ESD applications, the MLN for multiline protection and the AUML Series for automotive applications. Features Lead-Free Leadless 42, 3, 85, and 2 Chip Sizes Multilayer Ceramic Construction Technology -55 o C to +25 o C Operating Temperature Range Operating Voltage Range V M(DC) = 5.5V to 2V Rated for Surge Current (8 x 2µs) Rated for Energy ( x µs) Inherent Bi-directional Clamping No Plastic or Epoxy Packaging Assures Better than 94V- Flammability Rating Standard Low Capacitance Types Available Applications Suppression of Inductive Switching or Other Transient Events Such as EFT and Surge Voltage at the Circuit Board Level ESD Protection for Components Sensitive to IEC -4-2, MIL-STD-883C Method 5.7, and Other Industry Specifications (See Also the MLE or MLN Series) Provides On-Board Transient Voltage Protection for ICs and Transistors Used to Help Achieve Electromagnetic Compliance of End Products Replace Larger Surface Mount TVS Zeners in Many Applications Size Metric EIA

2 Absolute Maximum Ratings For ratings of individual members of a series, see Device Ratings and Specifications table. Continuous: ML SERIES Steady State Applied Voltage: DC Voltage Range (V M(DC) ) to 2 AC Voltage Range (V M(AC)RMS ) to 7 Transient: Non-Repetitive Surge Current, 8/2µs Waveform, (I TM ) to 5 Non-Repetitive Surge Energy, /µs Waveform, (W TM ) to.2 Operating Ambient Temperature Range (T A ) to + 25 Storage Temperature Range (T STG ) to + 5 Temperature Coefficient (αv) of Clamping Voltage (V C ) at Specified Test Current <. UNITS V V A J O C O C %/ O C Device Ratings and Specifications PART NUMBER CONTINUOUS WORKING VOLTAGE RATINGS (25 o C) SPECIFICATIONS (25 o C) NON- REPETITIVE SURGE CURRENT (8/2 s) NON- REPETITIVE SURGE ENERGY (/ s) CLAMPING VOLTAGE AT A (OR AS NOTED) (8/2 s) V M(DC) V M(AC) I TM W TM V C MIN V N(DC) NOMINAL VOLTAGE AT ma DC TEST CURRENT V N(DC) MAX TYPICAL CAPACITANCE AT f = MHz (V) (V) (A) (J) (V) (V) (V) (pf) C 3 SURFACE MOUNT VARISTORS V3.5MLA V3.5MLA V3.5MLA85L V3.5MLA V5.5MLA V5.5MLA42L V5.5MLA3 V5.5MLA85 V5.5MLA85L V5.5MLA V9MLA V9MLA42L V9MLA V9MLA85L V2MLA85L V4MLA V4MLA3 V4MLA85 V4MLA85L V4MLA

3 Device Ratings and Specifications (Continued) RATINGS (25 o C) SPECIFICATIONS (25 o C) CONTINUOUS WORKING VOLTAGE NON- REPETITIVE SURGE CURRENT (8/2 s) NON- REPETITIVE SURGE ENERGY (/ s) CLAMPING VOLTAGE AT A (OR AS NOTED) (8/2 s) NOMINAL VOLTAGE AT ma DC TEST CURRENT TYPICAL CAPACITANCE AT f = MHz PART NUMBER V M(DC) V M(AC) I TM W TM V C MIN V N(DC) V N(DC) MAX (V) (V) (A) (J) (V) (V) (V) (pf) C V8MLA V8MLA V8MLA V8MLA85L V8MLA V8MLA at 2.5A VMLA3 VMLA85 VMLA85L VMLA VMLA at 2.5A VMLA3 VMLA85L VMLA at 2.5A VMLA2L at 2.5A V33MLA V42MLA V48MLA at 2.5A V48MLA2L at 2.5A V56MLA VMLA2 V68MLA at 2.5A V85MLA2 V2MLA at 2.5A 2 at 2.5A NOTES:. L suffix is a low capacitance and energy version; Contact your Littelfuse Sales Representative for custom capacitance requirements. o 2. Typical leakage at 25 C<25A, maximum leakage A at V ; for 42 size, typical leakage <5A, maximum leakage <2A at V M(DC) M(DC). 3. Average power dissipation of transients for 42, 3, 85, and 2 sizes not to exceed.3w,.5w, W, W and 5W respectively. 7

4 Temperature De-rating When transients occur in rapid succession, the average power dissipation is the energy (watt-seconds) per pulse times the number of pulses per second. The power so developed must be within the specifications shown on the Device Ratings and Specifications table for the specific device. For applications exceeding 25 o C ambient temperature, the peak surge current and energy ratings must be derated as shown in Figure. PERCENT OF RATED VALUE AMBIENT TEMPERATURE ( o C) FIGURE. PEAK CURRENT AND ENERGY DERATING CURVE PERCENT OF PEAKVALUE O 5 MLA42 Limit VI Curves t t O = VIRTUAL ORIGIN OF WAVE t =TIME FROM % TO 9% OF PEAK t = VIRTUAL FRONT TIME =.25 x t t 2 = VIRTUAL TIME TO HALF VALUE (IMPULSE DURATION) EXAMPLE: FOR AN 8/2µs CURRENT WAVEFORM 8µs = t = VIRTUAL FRONT TIME 2µs = t 2 = VIRTUAL TIME TO HALF VALUE t 2 FIGURE 2. PEAK PULSE CURRENT TEST WAVEFORM FOR CLAMPING VOLTAGE TIME 3 SURFACE MOUNT VARISTORS V8MLA42 V4MLA42 V9MLA42 V5.5MLA FIGURE 3. LIMIT V-I CHARACTERISTIC FOR V5.5MLA42 TO V8MLA42 7

5 Maximum Transient V-I Characteristic Curves MLA42L Limit VI Curves V9MLA42L V5.5MLA42L..... FIGURE 4. LIMIT V-I CHARACTERISTIC FOR V9MLA42L VMLA3 VMLA3 V8MLA3 V4MLA3 V9MLA3 V5.5MLA3 V3.5MLA3.... FIGURE 5. LIMIT V-I CHARACTERISTIC FOR V3.5MLA3 TO VMLA3 VMLA85L VMLA85L V8MLA85L V4MLA85L V2MLA85L V9MLA85L V5.5MLA85L V3.5MLA85L.... FIGURE 6. LIMIT V-I CHARACTERISTIC FOR V3.5MLA85L TO VMLA85L 72

6 Maximum Transient V-I Characteristic Curves (Continued) VMLA85 V8MLA85 V4MLA85 V5.5MLA85 V3.5MLA FIGURE 7. LIMIT V-I CHARACTERISTIC FOR V3.5MLA85 TO VMLA85 3 SURFACE MOUNT VARISTORS V68MLA V56MLA V42MLA V33MLA VMLA V8MLA V4MLA V5.5MLA V3.5MLA.... FIGURE 6. LIMIT V- CHARACTERISTIC FOR V3.5MLA TO V68MLA LEAKAGE CLAMPING VOLTAGE V2MLA2 V85MLA2 VMLA2 V48MLA2, V48MLA2L VMLA2, VMLA2L µa VMLA2 V8MLA2 µa µa ma ma ma A A A A CURRENT (A) FIGURE 9. LIMIT V-I CHARACTERISTIC FOR V8MLA2 TO V2MLA2 73

7 Device Characteristics At low current levels, the V-I curve of the multilayer transient voltage suppressor approaches a linear (ohmic) relationship and shows a temperature dependent effect (Figure ). At or below the maximum working voltage, the suppressor is in a high resistance mode (approaching 6 Ω at its maximum rated working voltage). Leakage currents at maximum rated voltage are below 5µA, typically 25µA; for 42 size below µa, typically 5µA. SUPPRESSOR VOLTAGE IN PERCENT OF V NOM VALUE AT 25 o C (%) % o o o o 25 o C % E -9 E -8 E -7 E -6 E -5 E -4 E -3 E -2 SUPPRESSOR CURRENT (ADC ) FIGURE. TYPICAL TEMPERATURE DEPENDANCE OF THE CHARACTERISTIC CURVE IN THE LEAKAGE REGION Speed of Response The Multilayer Suppressor is a leadless device. Its response time is not limited by the parasitic lead inductances found in other surface mount packages. The response time of the Zinc Oxide dielectric material is less than nanosecond and the ML can clamp very fast dv/dt events such as ESD. Additionally, in real world applications, the associated circuit wiring is often the greatest factor effecting speed of response. Therefore, transient suppressor placement within a circuit can be considered important in certain instances. FIRED CERAMIC DIELECTRIC CLAMPING VOLTAGE (V) - VMLA Energy Absorption/Peak Current Capability Energy dissipated within the ML is calculated by multiplying the clamping voltage, transient current and transient duration. An important advantage of the multilayer is its interdigitated electrode construction within the mass of dielectric material. This results in excellent current distribution and the peak temperature per energy absorbed is very low. The matrix of semiconducting grains combine to absorb and distribute transient energy (heat) (Figure ). This dramatically reduces peak temperature; thermal stresses and enhances device reliability. As a measure of the device capability in energy and peak current handling, the VMLAA part was tested with multiple pulses at its peak current rating (5A, 8/2µs). At the end of the test,, pulses later, the device voltage characteristics are still well within specification (Figure 3) V5.5MLA TEMPERATURE ( o C) FIGURE 2. CLAMPING VOLTAGE OVER TEMPERATURE (V C AT A) PEAK CURRENT = 5A 8/2µs DURATION, s BETWEEN PULSES VOLTAGE VMLA METAL END TERMINATION DEPLETION REGION METAL ELECTRODES NUMBER OF PULSES FIGURE 3. REPETITIVE PULSE CAPABILITY DEPLETION REGION GRAINS FIGURE. MULTILAYER INTERNAL CONSTRUCTION 74

8 Soldering Recommendations The principal techniques used for the soldering of components in surface mount technology are Infrared (IR) re-flow, vapour phase re-flow and wave soldering. Typical profiles are shown in Figures 4, 5 and 6. When wave soldering, the ML suppressor is attached to the circuit board by means of an adhesive. The assembly is then placed on a conveyor and run through the soldering process to contact the wave. With IR and vapour phase reflow; the device is placed in a solder paste on the substrate. As the solder paste is heated, it re-flows and solders the unit to the board. The recommended solder for the ML suppressor is a 62/36/2 (Sn//Ag), /4 (Sn/) or 63/37 (Sn/). Littelfuse also recommends an RMA solder flux. The ML series varistor is also compatible with lead-free process conditions. Please contact your Littelfuse representative or visit for the latest update. Wave soldering is the most strenuous of the processes. To avoid the possibility of generating stresses due to thermal shock, a preheat stage in the soldering process is recommended, and the peak temperature of the solder process should be rigidly controlled. When using a reflow process, care should be taken to ensure that the ML chip is not subjected to a thermal gradient steeper than 4 degrees per second; the ideal gradient being 2 degrees per second. During the soldering process, preheating to within degrees of the solder s peak temperature is essential to minimize thermal shock. Examples of the soldering conditions for the ML suppressor are given in the tables below. Once the soldering process has been completed, it is still necessary to ensure that any further thermal shocks are avoided. One possible cause of thermal shock is hot printed circuit boards being removed from the solder process and subjected to cleaning solvents at room temperature. The boards must be allowed to cool gradually to less than 5 o C before cleaning. Termination Options Littelfuse offers three types of electrode termination finish for the Multilayer product series:. Silver/Platinum 2. Silver/Palladium 3. Nickel Barrier (available for 42-2 package size) (The ordering information section describes how to designate them.) TEMPERATURE ( o C) TEMPERATURE ( o C) TEMPERATURE ( o C) FIGURE 4. REFLOW SOLDER PROFILE WAVE 2 o C FIRST PREHEAT SECOND PREHEAT TIME (MINUTES) FIGURE 5. WAVE SOLDER PROFILE RAMP RATE >5 o C/s TEMPERATURE 222 o C PREHEAT DWELL PREHEAT ZONE TIME (MINUTES) TEMPERATURE 222 o C 4-8 SECONDS ABOVE 83 o C PREHEAT ZONE RAMP RATE <2 o C/s 4-8 SECONDS ABOVE 83 o C 3 SURFACE MOUNT VARISTORS TIME (MINUTES) FIGURE 6. VAPOR PHASE SOLDER PROFILE 75

9 Recommended Pad Outline C B NOTE NOTE: Avoid metal runs in this area. A TABLE : PAD LAYOUT DIMENSIONS PAD SIZE 2 SIZE DEVICE SIZE DEVICE 85 SIZE DEVICE 3 SIZE DEVICE DIMENSION IN MM IN MM IN MM IN MM A B C SIZE DEVICE IN MM

10 Mechanical Dimensions E 3 D W L SURFACE MOUNT VARISTORS CHIP SIZE DIMENSION IN MM IN MM IN MM IN MM D Max E.2 ±..5 ±.25.2 ±..5 ±.25.2 ±..5 ±.25.5 ±.8.4 ±.2 L 25 ± ±. 25 ± ±..79 ±.8 2. ±.2.63 ±.6.6 ±5 W. ± ±..6 ±.. ± ±.8.25 ±.2.32 ±.6.8 ±5 42 IN MM ±.6.25 ±5.39 ±.4. ±.2 ±.4.5 ± Ordering Information VXXML TYPES V 8 MLA X X X DEVICE FAMILY Littelfuse TVSS Device DC WORKING VOLTAGE MULTILAYER SERIES DESIGNATOR PACKING OPTIONS T: 3in (3mm) Diameter Reel H: 7in (78mm) Diameter Reel (Note) A: Bulk Pack END TERMINATION OPTION No Letter: Ag/Pt W: Ag/Pd N: Nickel Barrier (42-2 only). DEVICE SIZE: i.e 2 mil x mil (3MM X.5MM) CAPACITANCE OPTION No Letter: Standard L: Low Capacitance Version Standard Shipping Quantities DEVICE SIZE 3 INCH REEL ( T OPTION) 7 INCH REEL ( H OPTION) BULK PACK ( A OPTION) 2 8, 2, 25, 2, , 2,5 25 3, 2, N/A, N/A 77

11 Tape and Reel Specifications Conforms to EIA - 48-, Revision A Can be supplied to IEC Publication SYMBOL DESCRIPTION DIMENSIONS IN MILLIMETERS 42 Size 3, 85, & 2 Sizes A Width of Cavity Dependent on Chip Size to Minimize Rotation. B Length of Cavity Dependent on Chip Size to Minimize Rotation. K Depth of Cavity Dependent on Chip Size to Minimize Rotation. W Width of Tape 8 ±.2 F Distance Between Drive Hole Centers and Cavity Centers 3.5 ±.5 E Distance Between Drive Hole Centers and Tape Edge.75 ± P Distance Between Cavity Centers 2±.5 4 ± P 2 Axial Drive Distance Between Drive Hole Centers & Cavity Centers 2 ± P Axial Drive Distance Between Drive Hole Centers 4 ± D Drive Hole Diameter.55 ±.5 D Diameter of Cavity Piercing N/A.5 ±.5 T Top Tape Thickness Max D P P 2 E K B F W t D P A PLASTIC CARRIER TAPE EMBOSSED PAPER (42 SIZE ONLY) PRODUCT IDENTIFYING LABEL EMBOSSMENT TOP TAPE 8mm NOMINAL 78mm OR 3mm DIA. REEL 78