revised: january 7, 2009 131 ? 2009 littelfuse, inc. speci?cations are subject to change without notice. radial lead fuses 272/273/274/278/279 series please refer to www.littelfuse.com/series/272.html, /273.html, /274.html, /278.html or /279.html for current information. micro? > very fast-acting > 272/273/274/278/279 series 272-4/278-9 272/273/274/278/279 series, micro? very fast-acting fuse description developed originally for the u.s. space program, micro? fuse provides reliability in a compact design. the micro? fuse is available in plugCin or radial lead styles and a complete range of ampere ratings from 1/500 to 5a to suit a wide variety of design needs. agency approvals agency agency file number ampere range e10480 2ma - 5a lr 29862 2ma - 5a qp l fm02 2ma - 5a features electrical characteristics applications qpl % of ampere rating ampere rating opening time 100% 1/500C5 4 hours, min. 200% 1/500C3/10 5 seconds, max. 4/10-5 2 seconds, max. ampere rating (a) amp code (for all above series) max voltage rating (v) interrupting rating nominal cold resistance (ohms) nominal melting i 2 t (a 2 sec) agency approvals qp l .002 .002 125 10,000 amperes at 125 vac/vdc. 2200 0.0000000 0845 xxx .005 .005 125 280 0.00000000810 xxx .010 .010 125 80.0 0. 00000 0462 xxx .015 .015 125 44.0 0. 00000123 xxx .031 .031 125 16.0 0. 00000810 xxx .050 .050 125 3.20 0. 0000666 xxx .062 .062 125 2.32 0.000115 xxx .100 .100 125 1.25 0.000385 xxx .125 .125 125 1.0 0.000691 xxx .200 .200 125 2.30 0.00409 xxx .250 .250 125 1.75 0.00640 xxx .300 .300 125 1.25 0.00945 xxx .400 .400 125 0.227 0.0251 xxx .500 .500 125 0.167 0.0716 xxx .600 .600 125 0.430 0.0411 xxx .700 .700 125 0.324 0.0710 xxx .750 .750 125 0.293 0.0900 xxx .800 .800 125 0.271 0.113 xxx 1.00 001. 125 0.0880 0.0648 xxx 01.5 01.5 125 0.0578 0.160 xxx 2.00 002. 125 0.0425 0.300 xxx 3.00 003. 125 0.0275 0.759 xxx 4.00 004. 125 0.0202 1.38 xxx 5.00 005. 125 0.0156 2.21 xxx electrical characteristics military grade available t high breaking capacity t clear cover option to view t fuse element status available from very low t ampere of 2ma to 5a plug-in with short or long t leads option printed circuit boards t and similar equipment electronic components t
revised: january 7, 2009 introduction to circuit protection introduction to circuit protection transientology 132 ? 2009 littelfuse, inc. speci?cations are subject to change without notice. radial lead fuses 272/273/274/278/279 series please refer to www.littelfuse.com/series/272.html, /273.html, /274.html, /278.html or /279.html for current information. micro? > very fast-acting > 272/273/274/278/279 series average time current curves 100 10 1 0.1 0.01 0.001 1 10 100 0.01 0.1 0.005 1/64 a 1/100 a 1/200 a 1/32 a 1/16 a 1/8 a 1/4 a 1/2 a 3/4 a 1 a 1 1/2 a 2 a 3 a 4 a 5 a time in seconds current in amperes temperature rerating curve soldering parameters - wave soldering dwell t ime 0 20 4 0 60 80 100 120 1 4 0 160 180 200 220 2 4 0 260 280 300 0 10 20 30 4 0 5 0 60 70 80 90 100 110 120 130 1 4 0 1 5 0 160 170 180 190 200 210 220 230 2 4 0 t ime (seconds) t emperature (c) - measured on bottom side of board cooling t ime preheat t ime wave parameter lead-free recommendation preheat: (depends on flux activation temperature) (typical industry recommendation) temperature minimum: 100 c temperature maximum: 150 c preheat time: 60-180 seconds solder pot temperature: 260 c maximum solder dwell time: 2-5 seconds recommended hand-solder parameters: solder iron temperature: 350 c +/- 5c heating time: 5 seconds max. note: these devices are not recommended for ir or convection re?ow process. recommended process parameters:
revised: january 7, 2009 133 ? 2009 littelfuse, inc. speci?cations are subject to change without notice. radial lead fuses 272/273/274/278/279 series please refer to www.littelfuse.com/series/272.html, /273.html, /274.html, /278.html or /279.html for current information. micro? > very fast-acting > 272/273/274/278/279 series 272-4/278-9 product characteristics operating temperature: 273 and 279: C55oc to +85oc; 272 and 278: C55oc to +125oc fuses to mil spec 273 series is available in csa lr 29862. military qpl type (fm02). to order, change 273 to 274. materials 272 and 278 series cap: nickel plated brass 273, 274 and 279 series cap: mirror polished polycarbonate base: r-4 ryton pins: tin plated copper product marking current and voltage ratings stamped on cap dimensions 7.30 (.29 " ) (.17 " ) 8.89 (.35 " ) 2.54 (.10 " ) 7.30 (.29 " ) 25.4 (1.0 " ) 2.54 (.10 " ) 25.4 (1.0 " ) 2.54 (.10 " ) 5.97 (.235 " ) 6.35 (.25 " ) 5.97 (.235 " ) 2.54 (.10 " ) 8.89 (.35 " ) 6.35 (.25 " ) 272 000 series 273 000 and 274 000 series 278 000 series 279 000 series (short lead, metal cap) (short lead, clear plastic cap) (long lead, metal cap) (long lead, clear plastic cap) note: amperage and voltage rating stamped on cap. leads are tin plated copper; .025 " diameter. (.17 " ) 4.32 4.32 part numbering system 0273 xxxx v packaging code amp. code series refer to amp code column of electrical characteristics table v = 5 h = 100 packaging packaging option packaging speci?cation quantity quantity & packaging code bulk n / a 5 v bulk n / a 100 h
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