ML Varistor Series. Surface Mount Varistors

Transcription

1 Pb 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 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 Leadless 42, 6, 85, 126 and 12 Chip Sizes Multilayer Ceramic Construction Technology -55 o C to +125 o C Operating Temperature Range Operating Voltage Range V M(DC) = 5.5V to 12V 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 % Lead-Free 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 6-4-2, MIL-STD-88C Method 15.7, 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 12 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 1.2 Operating Ambient Temperature Range (T A ) to Storage Temperature Range (T STG ) to + 15 Temperature Coefficient (V) of Clamping Voltage (V C ) at Specified Test Current <.1 UNITS V V A J O C O C %/ O C Device Ratings and Specifications RATINGS (125 o C) SPECIFICATIONS (25 o C) CONTINUOUS WORKING VOLTAGE NON- REPETITIVE SURGE CURRENT (8/2µs) NON- REPETITIVE SURGE ENERGY (/µs) CLAMPING VOLTAGE AT A (OR AS NOTED) (8/2µs) NOMINAL VOLTAGE AT 1mA DC TEST CURRENT TYPICAL CAPACITANCE AT f = 1MHz 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 V.5MLA at 2A V.5MLA at 5A V.5MLA85L at 2A V.5MLA V5.5MLA at 1A V5.5MLA42L at 1A V5.5MLA at 2A V5.5MLA at 5A V5.5MLA85L at 2A V5.5MLA V9MLA at 1A V9MLA42L at 1A V9MLA at 2A V9MLA85L at 2A V12MLA85L at 2A V14MLA at 1A V14MLA at 2A V14MLA at 5A V14MLA85L at 2A V14MLA

3 Device Ratings and Specifications (Continued) RATINGS (125 o C) SPECIFICATIONS (25 o C) PART NUMBER CONTINUOUS WORKING VOLTAGE NON- REPETITIVE SURGE CURRENT (8/2µs) NON- REPETITIVE SURGE ENERGY (/µs) CLAMPING VOLTAGE AT A (OR AS NOTED) (8/2µs) V M(DC) V M(AC) I TM W TM V C MIN V N(DC) NOMINAL VOLTAGE AT 1mA DC TEST CURRENT TYPICAL CAPACITANCE AT f = 1MHz V18MLA at 1A V18MLA at 2A V18MLA at 5A V18MLA85L at 2A V18MLA V18MLA V26MLA at 2A V26MLA at 5A V26MLA85L at 2A V26MLA V26MLA VMLA at 2A VMLA85L at 2A VMLA VMLA12L VMLA V42MLA V48MLA V48MLA12L V56MLA V6MLA V68MLA V85MLA V12MLA NOTES: 1. 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<25µA, maximum leakage 5µA at V M(DC) ; for 42 size, typical leakage <5µA, maximum leakage <2µA at V M(DC).. Average power dissipation of transients for 42, 6, 85, 126 and 12 sizes not to exceed.w,.5w,.1w,.1w and.15w respectively. V N(DC) MAX (V) (V) (A) (J) (V) (V) (V) (pf) C 165

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 125 o C ambient temperature, the peak surge current and energy ratings must be derated as shown in Figure 1. PERCENT OF RATED VALUE AMBIENT TEMPERATURE ( o C) FIGURE 1. PEAK CURRENT AND ENERGY DERATING CURVE PERCENT OF PEAK VALUE O 1 5 t t 1 O 1 = VIRTUAL ORIGIN OF WAVE t = TIME FROM % TO 9% OF PEAK t 1 = VIRTUAL FRONT TIME = 1.25 x t t 2 = VIRTUAL TIME TO HALF VALUE (IMPULSE DURATION) EXAMPLE: FOR AN 8/2µs CURRENT WAVEFORM 8µs = t 1 = VIRTUAL FRONT TIME 2µs = t 2 = VIRTUAL TIME TO HALF VALUE t 2 FIGURE 2. PEAK PULSE CURRENT TEST WAVEFORM FOR CLAMPING VOLTAGE TIME CLAMPING VOLTAGE LEAKAGE V18MLA42 V14MLA42 V9MLA42 V5.5MLA42 µa µa 1mA ma ma 1A A A FIGURE. LIMIT V-I CHARACTERISTIC FOR V5.5MLA42 TO V18MLA42 166

5 Maximum Transient V-I Characteristic Curves LEAKAGE CLAMPING VOLTAGE V9MLA42L µa µ A 1mA ma ma 1A A FIGURE 4. LIMIT V-I CHARACTERISTIC FOR V9MLA42L CLAMPING VOLTAGE LEAKAGE VMLA6 V26MLA6 V18MLA6 V14MLA6 V9MLA6 V5.5MLA6 V.5MLA6 µa µa 1mA ma ma 1A A A FIGURE 5. LIMIT V-I CHARACTERISTIC FOR V.5MLA6 TO VMLA6 CLAMPING VOLTAGE LEAKAGE VMLA85L V26MLA85L V18MLA85L V14MLA85L V9MLA85L V5.5MLA85L V.5MLA85L µa µa 1mA ma ma 1A A A FIGURE 6. LIMIT V-I CHARACTERISTIC FOR V.5MLA85L TO VMLA85L 167

6 Maximum Transient V-I Characteristic Curves (Continued) CLAMPING VOLTAGE LEAKAGE V26MLA85 V18MLA85 V14MLA85 V5.5MLA85 V.5MLA85 µa µa 1mA ma ma 1A A A A FIGURE 7. LIMIT V-I CHARACTERISTIC FOR V.5MLA85 TO V26MLA85 V68MLA126 V56MLA126 V42MLA126 VMLA126 V26MLA126 V18MLA126 V14MLA126 V5.5MLA126 V.5MLA126 LEAKAGE CLAMP VOLTAGE 1 µa µa 1mA ma ma 1A A A A FIGURE 8. LIMIT V-I CHARACTERISTIC FOR V.5MLA126 TO V68MLA126 LEAKAGE CLAMPING VOLTAGE V12MLA12 V85MLA12 V6MLA12 V48MLA12, V48MLA12L VMLA12, VMLA12L 1 V26MLA12 V18MLA12 µa µa 1mA ma ma 1A A A A FIGURE 9. LIMIT V-I CHARACTERISTIC FOR V18MLA12 TO V12MLA12 168

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 125 o C % 1E -9 1E -8 1E -7 1E -6 1E -5 1E -4 1E - 1E -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 1 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) 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 11). 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 V26MLA126A part was tested with multiple pulses at its peak current rating (15A, 8/2µs). At the end of the test,, pulses later, the device voltage characteristics are still well within specification (Figure 1) V26MLA126 V5.5MLA TEMPERATURE ( o C) FIGURE 12. CLAMPING VOLTAGE OVER TEMPERATURE (V C AT A) PEAK CURRENT = 15A 8/2µs DURATION, s BETWEEN PULSES VOLTAGE V26MLA126 METAL END TERMINATION DEPLETION REGION METAL ELECTRODES NUMBER OF PULSES FIGURE 1. REPETITIVE PULSE CAPABILITY DEPLETION REGION GRAINS FIGURE 11. MULTILAYER INTERNAL CONSTRUCTION 169

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 14, 15 and 16. 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 62/6/2 (Sn/Pb/Ag), 6/4 (Sn/Pb) or 6/7 (Sn/Pb). Littelfuse also recommends an RMA solder flux. 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: 1. Silver/Platinum 2. Silver/Palladium. Nickel Barrier (Tin-on-Nickel-on-Silver, available for package size) (The ordering information section describes how to designate them.) TEMPERATURE ( o C) TEMPERATURE ( o C) TEMPERATURE 222 o C PREHEAT DWELL PREHEAT ZONE FIGURE 14. REFLOW SOLDER PROFILE WAVE 26 o C FIRST PREHEAT RAMP RATE <2 o C/s TIME (MINUTES) 4-8 SECONDS ABOVE 18 o C SECOND PREHEAT TIME (MINUTES) FIGURE 15. WAVE SOLDER PROFILE TEMPERATURE ( o C) RAMP RATE >5 o C/s TEMPERATURE 222 o C 4-8 SECONDS ABOVE 18 o C PREHEAT ZONE TIME (MINUTES) FIGURE 16. VAPOR PHASE SOLDER PROFILE 17

9 Recommended Pad Outline C B NOTE NOTE: Avoid metal runs in this area. A TABLE 1: PAD LAYOUT DIMENSIONS PAD SIZE 12 SIZE DEVICE 126 SIZE DEVICE 85 SIZE DEVICE 6 SIZE DEVICE DIMENSION IN MM IN MM IN MM IN MM A B C SIZE DEVICE IN MM

10 Mechanical Dimensions E D L W CHIP SIZE DIMENSION IN MM IN MM IN MM IN MM D Max E.2 ±.1.5 ±.25.2 ±.1.5 ±.25.1 to.29.5 to ±.8.4 ±.2 L.125 ±.12.2 ±..125 ±.12.2 ±..79 ± ±.2.6 ± ±.15 W. ± ±..6 ± ± ± ±.2.2 ±.6.8 ± IN MM ±.6.25 ±.15.9 ±.4 1. ±.1.2 ±.4.5 ±.1 Ordering Information VXXML TYPES V 18 MLA 126 X X X DEVICE FAMILY Littelfuse TVSS Device DC WORKING VOLTAGE MULTILAYER SERIES DESIGNATOR PACKING OPTIONS T: 1in (mm) Diameter Reel H: 7in (178mm) Diameter Reel (Note) A: Bulk Pack END TERMINATION OPTION No Letter: Ag/Pt W: Ag/Pd N: Nickel Barrier (Tin-on-Nickel-on-Silver, only) DEVICE SIZE: i.e 12 mil x 6 mil (MM X 1.5MM) CAPACITANCE OPTION No Letter: Standard L: Low Capacitance Version Standard Shipping Quantities DEVICE SIZE 1 INCH REEL ( T OPTION) 7 INCH REEL ( H OPTION) BULK PACK ( A OPTION) 12 8, 2, , 2, , 2,5 25 6, 2, N/A, N/A 172

11 Tape and Reel Specifications Conforms to EIA , Revision A Can be supplied to IEC Publication SYMBOL DESCRIPTION DIMENSIONS IN MILLIMETERS 42 Size 6, 85, 126 & 12 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.5 ±.5 E Distance Between Drive Hole Centers and Tape Edge 1.75 ±.1 P 1 Distance Between Cavity Centers 2±.5 4 ±.1 P 2 Axial Drive Distance Between Drive Hole Centers & Cavity Centers 2 ±.1 P Axial Drive Distance Between Drive Hole Centers 4 ±.1 D Drive Hole Diameter 1.55 ±.5 D 1 Diameter of Cavity Piercing N/A 1.5 ±.5 T 1 Top Tape Thickness.1 Max D P P 2 E K B F W t 1 D 1 P 1 A PLASTIC CARRIER TAPE EMBOSSED PAPER (42 SIZE ONLY) PRODUCT IDENTIFYING LABEL EMBOSSMENT TOP TAPE 8mm NOMINAL 178mm OR mm DIA. REEL 17