Axial Lead & Cartridge Fuses PICO® ll > Very Fast-Acting Fuse > 251/253 Series 251/253 Series, PICO® II Very Fast-Acting Fuse PS QPL E Description The PICO® II Very Fast-Acting Fuse is designed to meet an extensive array of performance characteristics in a space-saving subminiature package. Features • Very fast-acting • Halogen-free available • Small size • Wide operating • Wide current rating range temperature range (0.062A- 15A) • Low temperature re-rating Applications Agency Approvals Agency File Number Secondary protection for space constrained applications Agency Ampere Range 253 Series 251 Series • Flat–panel display TV • Power supply E10480 0.062A - 15A • LCD monitor • Audio/Video system 29862 0.062A - 15A • LCD backlight inverter • Lighting system PES PSE_NBK200416-JP1021 1A - 5A • Office machines • Medical equipment J50158379 0.500A - 10A FM10 N/A 0.062A - 15A Electrical Characteristics for Series 0.500A, 1A, 2A, 2.5A, 3A, 2020970207000061 4A, 5A % of Ampere Ampere Rating Opening Time Rating Note: See Electrical Specifications by Item table for specific approved ratings. 100% 0.062A - 15A 4 Hours, Min. 0.062A - 7A 1 Second, Max. 200% 10A 3 Seconds, Max. 12 - 15A 10 Seconds, Max. 0.500A, 1A, 2A, 275% 2.5A, 3A, 4A, 5A, 300 msecs., Max. Additional Information 7A, 10A 0.5A, 1A, 2A, 2.5A, 400% 30 msecs., Max. 3A, 4A, 5A, 7A, 10A 0.500A, 1A, 2A, 1000% 2.5A, 3A, 4A, 5A, 4 msecs., Max. 7A, 10A Datasheet Resources Samples 251 Series 251 Series 251 Series Datasheet Resources Samples 253 Series 253 Series 253 Series © 2020 Littelfuse, Inc. Specifications are subject to change without notice. Revised: GD.10/14/20

Axial Lead & Cartridge Fuses PICO® ll > Very Fast-Acting Fuse > 251/253 Series Electrical Specifications by Item Agency Approvals Max Nominal Nom Ampere Ordering Ordering Nominal Amp Voltage Interrupting Cold Voltage QPL Rating Number Number Melting Code Rating Rating Resistance Drop PS 253 (A) (Std.) (Mil.) (V) (Ohms) I2t (A2 sec) (V) E SOenrileys .062 .062 251.062 253.062 125 7.000 0.000113 1.4 x x - - x - .125 .125 251.125 253.125 125 1.700 0.00174 0.285 x x - - x - .200 .200 251.200 253.200 125 0.895 0.0048 0.345 x x - - - - .250 .250 251.250 253.250 125 0.665 0.0116 0.24 x x - - x - .375 .375 251.375 253.375 125 0.395 0.0296 0.215 x x - - x - .500 .500 251.500 253.500 125 0.302 0.0598 0.2165 x x - x x x .630 .630 251.630 125 0.205 0.08 0.188 x x - - - - .750 .750 251.750 253.750 125 0.175 0.153 0.176 x x - x x - 1.00 001. 251001. 253001. 125 0.128 0.256 0.194 x x x x x x 300 A @ 1.25 1.25 2511.25 125 125VDC 0.100 0.390 0.2 x x x - - - 1.50 01.5 25101.5 25301.5 125 0.0823 0.587 0.21 x x x x x - 2.00 002. 251002. 253002. 125 50A@ 0.0473 0.405 0.141 x x x x x x 125VAC 2.50 02.5 25102.5 125 0.0360 0.721 0.132 x x x x - x 3.00 003. 251003. 253003. 125 0.0295 1.19 0.131 x x x x x x 3.50 03.5 25103.5 125 0.0240 1.58 0.1205 x x x x - - 4.00 004. 251004. 253004. 125 0.0204 2.45 0.114 x x x x x x 5.00 005. 251005. 253005. 125 0.0158 4.14 0.11 x x x x x x 7.00 007. 251007. 253007. 125 0.0107 10.4 0.102 x x - x x - 10.0 010. 251010. 253010. 125 0.0072 25.5 0.1 x x - x x - 12.0 012. 251012. 32 300A@32VDC 0.0059 45.2 0.0878 x x - - - - 15.0 015. 251015. 253015. 32 & 50A@32VAC 0.00446 68.8 0.071 x x - - x - Note: Higher ampere ratings are available. Please contact Littelfuse Technical Support or your Littelfuse products representative for assistance. Temperature Re-rating Curve Average Time Current Curves 100 .062A .125A .250A.375A.500A.630A.750A1A1.25A1.5A2A2.5A3A3.5A4A5A7A10A12A15A 10 S D N O C 1 E S N E I M TI 0.1 Note: 1. Re-rating depicted in this curve is in addition to the standard derating of 25% for continuous operation. 0.01 0.001 0.050.1 1 10 100 1000 CURRENT IN AMPERES © 2020 Littelfuse, Inc. Specifications are subject to change without notice. Revised: GD.10/14/20

Axial Lead & Cartridge Fuses PICO® ll > Very Fast-Acting Fuse > 251/253 Series Product Characteristics Encapsulated, Epoxy-coated Body MIL-STD-202, Method 201 (10–55 Hz); Materials 251 Series: Pure tin-coated copper wire leads Vibration Method 204, Test Condition C (55–2000 253 Series: Solder-coated copper wire leads Hz at 10 G’s Peak) Solderability MIL-STD-202, Method 208 MIL-STD-202, Method 213, Test Shock Condition I (100 G’s peak for 6 msecs.) MIL-STD-202, Method 211, Test Condition A Lead Pull Force (will withstand a 7lbs. axial pull test) Insulation Resistance MIL-STD-202, Method 302, Test Condition A (10,000 ohms Fuses To MIL For fuses to MIL-PRF-23419, FM10 change the (After Opening): minimum at 100 volts) series number from SPEC 251 to 253 Moisture Resistance MIL-STD-202, Method 106 Operating Resistance to Withstands 60 seconds above 200OC –55ºC to +125ºC (Consider re-rating) Temperature Soldering Heat and up to 260ºC, maximum Flammability Rating UL 94V–0 Soldering Parameters Recommended Process Parameters: Packaging Lead-Free Recommendation Wave Parameter for 251 Series only Packaging Quantity & Packaging Option Specification Packaging Code Preheat: (Depends on Flux Activation Temperature) (Typical Industry Recommendation) *T1: 52.4mm (2.062") EIA 296 Please refer to Temperature Minimum: 100°C Tape and Reel available quantities Temperature Maximum: 150°C above in "Part **T3: 73mm (2.874') EIA 296 Numbering System” Preheat Time: 60-180 seconds Tape and Reel Solder Pot Temperature: 260°C Maximum The default lead length for both ammo pack and loose pack is T1 for 251 and is T3 for 253. Solder Dwell Time: 2-5 seconds Notes: * T1 dimension is defined as the length of the component between the two tapes. The full component length Recommended Hand Soldering Parameters: is 62.7mm (2.468"). T1 length is for 251 series only. Solder Iron Temperature: 350°C +/- 5°C ** T3 dimension is defined as the length of the component between the two tapes. The full component length Heating Time: 5 seconds max. is 83.3.7mm (3.28”). T3 length is for 253 series only. Note: These devices are not recommended for IR or Convection Reflow process Dimensions Part Numbering System 251 Series Markings 0251 xxxx N R T1 L (T1 lead length) 62.7 (2.468") 52.4 (2.062")* Series 27.78 27.78 251 = Standard type (1.094") 7.11 (.280") (1.094") 253 = Military type 1 A LF Current Rating 2.80 Refer to Amp Code column of 6.35 (.25") 5.0 (.197") (.11") 6.35 (.25") Electrical Specifications Table tape MAX tape Quantity 1 A LF N = 5000 Wire Diameter: P = 2000 00..6841 ((..002352"")) ffoorr 01.20-6125- 1a0m apmp, M = 1000 H = 100 Type of Packaging 225511 SSeerriieess ((HHaallooggeenn--ffrreeee VVeerrssiioonn)) MMaarrkkiinnggss 253 Series Markings ((TT11 lleeaadd lleennggtthh)) (T3 lead length) R = Reel 6622..77 ((22..446688"")) 83.31 (3.28") A = Ammo Pack 5522..44 ((22..006622""))** X = Loose Pack 2277..7788 2277..7788 38.1 73.0 (2.874")** 38.1 ((11..009944"")) 77..1111 ((..228800"")) ((11..009944"")) (1.5") 7.11 (.280") (1.5") Lead Length The default lead length for Ammo pack and LLFF 11 AA LF 1 A Loose pack is now T1 for 251 series, and 22..8800 6.35 (.25") 5.0 (.197") 2.6M1 (A.1X03") 6.35 (.25") rTe1m =a i5n2s. T43m fmor (22665...03336tt55 aas2 pp((e”..ee22r)55i,e ""2s))5, 1th se55er..00eri fe((o..s11r 99eo77:n""))ly* ((MM..11AA11XX"")) 66..33tt55aa pp((..ee2255"")) tape tape Blank = 52.4mm (2.062”) for 251 series* 11 AA LLFF LF 1 A or 73mm (2.874”) for 253 sWWeriiirreees DD*ii*aammeetteerr:: Wire Diameter: Option Codes 0000....66884411 ((((....000022335522"""")))) ffffoooorrrr 0011..2266--2211--5511 00aa..mm00 ppaammpp,, 0.64 (.025") for 0.062-10 amp, L = RoHS + HF 0.81 (.032") for 15 amp (Only applies to 251 Series) 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. © 2020 Littelfuse, Inc. Specifications are subject to change without notice. Revised: GD.10/14/20