? 2017 littelfuse, inc. specifcations are subject to change without notice. revised: 09/14/17 description the littelfuse 20mm smd series is a surface-mount metal oxide varistor device, for use in applications requiring hi-energy / transient current capability. the ac rated parts are designed to operate continuously across ac power lines. the dc rated parts are suitable for automotive applications. the series comprises a nylon molded package with folded tin plated metal leads for soldering to board. the smd series is based on radial 20mm internal varistor element with similar characteristics to the littelfuse la / za series of varistors. features ? dc voltage rating 26 - 420vdc ? ac voltage rating 20vac - 320ac ? no de-rating up to 85c ambient ? lead-free, halogen- free and rohs compliant ? low voltage devices specifed for automotive load dump energy ? available in "waf ? e" tray packaging agency approvals absolute maximum ratings ? for ratings of individual members of a series, see device ratings and specifcations chart continuous SM20 series units steady state applied voltage: ac voltage range (v m(ac)rms ) 20 to 320 v dc voltage range (v m(dc) ) 26 to 420 v transients: peak pulse current (i tm ) 8/20 s current wave, single pulse up to 6500 a single pulse energy capability (w tm ) 10/1000 s current wave 165 j load dump energy capability (td>=30ms) 160 j operating ambient temperature range (t a ) -40 to +85 o c storage temperature range (t stg ) -55 to +125 o c temperature coeffcient (a v ) of clamping voltage (v c ) at specifed test current <0.01 %/ o c hi-pot encapsulation (coating isolation voltage capability) (dielectric must withstand indicated dc voltage for one minute per mil-std 202, method 301) 2500 v coating insulation resistance 1000 m caution: stresses above those listed in absolute maximum ratings may cause permanent damage to the device. this is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specifcation is not implied. SM20 varistor series ohs agency agency approval agency file number ul1449 e320116 additional information datasheet ales resources metal-oxide varistors (movs) surface mount varistors > SM20 series
? 2017 littelfuse, inc. specifcations are subject to change without notice. revised: 09/14/17 repetitive surge capability v175SM20 - v320SM20 10,000 2,000 200 100 50 20 10 5 2 500 20 100 1,000 10,000 impulse dura tion ( s) surge current (a) 1 2 10 4 10 5 10 6 model size 20mm v175SM20 - v320SM20 10 3 indefinite 1,000 10 2 10 5,000 1 for applications exceeding 85oc ambient temperature, the peak surge current and energy ratings must be reduced as shown below peak pulse current test waveform for clamping voltage peak current, energy and power derating curve 0 1 = virtual origin of wave t = time from 10% to 90% of peak t 1 = rise time = 1.25 x t t 2 = decay time example - for an 8/20 s current waveform: 8 s = t 1 = rise time 20 s = t 2 = decay time o v s m o 10 0 90 80 70 60 50 40 30 20 10 0 -55 50 60 70 80 90 10 01 10 12 01 30 14 01 50 ambient temper a ture ( o c) percent of ra ted v alue figure 1. current , energy and po wer der a ting cur ve SM20 series ratings & specifcations maximum rating (85c) specifcations (25c) continuous transient varistor voltage at 1ma dc test current maximum clamping voltage 8 x 20 s typical capacitance f = 1mhz v rms v dc energy 10 x 1000 s peak current 8 x 20s part number branding v m(ac) v m(dc) w tm 1x pulse i tm 1x pulse v nom min v nom max v c i pk c (v) (v) (j) (a) (v) (v) (v) (a) (pf) v26SM20 26SM20 20 26 20 160 (note 1) 2000 32 (10ma) 40 (10ma) 63 20 12000 v175SM20 175SM20 175 225 90 6500 247 303 455 100 1400 v230SM20 230SM20 230 300 122 6500 324 396 595 100 110 0 v250SM20 250SM20 250 330 130 6500 354 429 650 100 1000 v275SM20 275SM20 275 369 140 6500 389 473 710 100 900 v300SM20 300SM20 300 405 165 6500 420 517 775 100 800 v320SM20 320SM20 320 420 150 6500 462 540 810 100 750 1. energy rating for impulse duration of 30ms minimum to one half of peak current (automotive load dump). metal-oxide varistors (movs) surface mount varistors > SM20 series
? 2017 littelfuse, inc. specifcations are subject to change without notice. revised: 09/14/17 lead (pb) soldering recommendations the principal techniques used for the soldering of components in surface mount technology are ir re- ? ow and wave soldering. typical profles are shown on the right. the terminals of SM20 series devices are tin plated copper, and the recommended solder is 62/36/2 (sn/pb/ag), 60/40 (sn/pb) or 63/37 (sn/pb). littelfuse also recommends an rma solder ?ux. 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 re? ow process, care should be taken to ensure that the SM20 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 100 degrees of the solder's peak temperature is essential to minimize thermal shock. 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 50oc before cleaning. leadCfree (pb-free) soldering recommendations the terminals of SM20 series devices are tin plated copper, and the recommended lead-free solder is 96.5/3.0/0.5 (snagcu) with an rma ?ux, though there is a wide selection of pastes and ? uxes available that should be compatible. the re ? ow profle must be constrained by the maximums in the leadCfree re ? ow profle. for leadCfree wave soldering, the wave solder profle still applies. note: the leadCfree paste, ? ux and profle were used for evaluation purposes by littelfuse, based upon industry standards and practices. there are multiple choices of all three available, it is advised that the customer explores the optimum combination for their process as processes vary considerably from site to site. figure 14 . refl ow solder pr ofile figure 15 .w a ve solder pr ofile figure 16 . lead-free re-flow solder pr ofile time (minutes) 30 0 250 20 0 15 0 10 0 50 0 0.0 0.5 1. 01 .5 2.0 2.5 3.0 3.5 4.0 4.5 maximum wa ve 260c second prehea t firs t prehea t maximum temper at ure 250?c, time within 5?c of peak 20 seconds maximum prehea t zone r amp ra te <3?c/s 60 - 1 50 sec > 21 7?c prehea t zone prehea t d well r amp ra te <2c/s maximum temper a ture 230c temper a ture c time (minutes) 250 20 0 15 0 10 0 50 0 0 0.5 1 .0 1 .5 2.0 2.5 3.0 3.5 4.0 40-80 seconds abo ve 1 83c temper a ture c temper a ture c time (minutes) 30 0 250 20 0 15 0 10 0 50 0 0 1 .0 2.0 3.0 4.0 5.0 6.0 7. 0 figure 14 . refl ow solder pr ofile figure 15 .w a ve solder pr ofile figure 16 . lead-free re-flow solder pr ofile time (minutes) 30 0 250 20 0 15 0 10 0 50 0 0.0 0.5 1. 01 .5 2.0 2.5 3.0 3.5 4.0 4.5 maximum wa ve 260c second prehea t firs t prehea t maximum temper at ure 250?c, time within 5?c of peak 20 seconds maximum prehea t zone r amp ra te <3?c/s 60 - 1 50 sec > 21 7?c prehea t zone prehea t d well r amp ra te <2c/s maximum temper a ture 230c temper a ture c time (minutes) 250 20 0 15 0 10 0 50 0 0 0.5 1 .0 1 .5 2.0 2.5 3.0 3.5 4.0 40-80 seconds abo ve 1 83c temper a ture c temper a ture c time (minutes) 30 0 250 20 0 15 0 10 0 50 0 0 1 .0 2.0 3.0 4.0 5.0 6.0 7. 0 figure 14 . refl ow solder pr ofile figure 15 .w a ve solder pr ofile figure 16 . lead-free re-flow solder pr ofile time (minutes) 30 0 250 20 0 15 0 10 0 50 0 0.0 0.5 1. 01 .5 2.0 2.5 3.0 3.5 4.0 4.5 maximum wa ve 260c second prehea t firs t prehea t maximum temper at ure 250?c, time within 5?c of peak 20 seconds maximum prehea t zone r amp ra te <3?c/s 60 - 1 50 sec > 21 7?c prehea t zone prehea t d well r amp ra te <2c/s maximum temper a ture 230c temper a ture c time (minutes) 250 20 0 15 0 10 0 50 0 0 0.5 1 .0 1 .5 2.0 2.5 3.0 3.5 4.0 40-80 seconds abo ve 1 83c temper a ture c temper a ture c time (minutes) 30 0 250 20 0 15 0 10 0 50 0 0 1 .0 2.0 3.0 4.0 5.0 6.0 7. 0 refow solder profle wave solder profle leadCfree re-fow solder profle metal-oxide varistors (movs) surface mount varistors > SM20 series
? 2017 littelfuse, inc. specifcations are subject to change without notice. revised: 09/14/17 part numbering system for ?varistor? max voltage rating m(ac) (two or three digits -- refer to ratings and speci?cations table) v 275 SM20 SM20 series 8 6 3 8 s1 s2 soldering pad layout h1 h2 t w d product dimensions symbol millimeters min max d (diameter) --- 26 h1 --- 10.5 h2 1. 0 -- t 0.50 0.70 s1 32.5 35 s2 3.0 4.5 w 6.2 6.6 packaging 192 mm 30 mm typical 192 mm 30 mm typical 8.4 mm typical radius 30 mm typical 11.7 mm pocket depth standard packaging is in "waf ? e" trays: quantity per tray: 36 pieces quantity per box: 108 pieces operating ambient temperature range (t a ) -40c to +85c storage temperature range(t stg ) -55c to 125c solvent resistance mil std 202, method 215 moisture sensitivity level 1, j-std-020 lead material folded tin plated metal leads soldering characteristics j-std-002 coating molded plastic meets ul94 v-0 requirement physical specifcations environmental specifcations disclaimer notice - information furnished is believed to be accurate and reliable. however, users should independently evaluate the suitability of and test each product selected for their own applications. littelfuse products are not designed for, and may not be used in, all applications. read complete disclaimer notice at www.littelfuse.com/disclaimer-electronics . metal-oxide varistors (movs) surface mount varistors > SM20 series
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