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© 2017 Littelfuse, Inc.
Specifications are subject to change without notice.
Revised: 03/03/17
Axial Lead & Cartridge Fuses
PICO
®
ll > Very Fast-Acting Fuse > 251/253 Series
Materials
Encapsulated, Epoxy-Coated
Body: Pure Tin-coated Copper wire leads
Solderability MIL-STD-202, Method 208
Lead Pull Force
MIL-STD-202, Method 211, Test Condition
A (will withstand a 7lbs. axial pull test)
Fuses To MIL SPEC
For fuses to MIL-PRF-23419, FM10
change the series number from
251 to 253
Operating
Temperature
–55ºC to +125ºC (Consider re-rating)
Product Characteristics
Vibration
MIL-STD-202, Method 201 (10–55
Hz); Method 204, Test Condition C
(55–2000 Hz at 10 G’s Peak)
Shock
MIL-STD-202, Method 213, Test
Condition I (100 G’s peak for 6
msecs.)
Insulation Resistance
(After Opening):
MIL-STD-202, Method 302,
Test Condition A (10,000 ohms
minimum at 100 volts)
Moisture Resistance MIL-STD-202, Method 106
Resistance to Soldering
Heat
Withstands 60 seconds above 200
O
C
and up to 260ºC, maximum
Flammability Rating UL 94V–0
Dimensions
Packaging
Part Numbering System
Packaging Option
Packaging
Specification
Quantity &
Packaging Code
*T1: 52.4mm (2.062")
Tape and Reel
EIA 296
Please refer to
available quantities
above in "Part
Numbering
System”
**T3: 73mm (2.874')
Tape and Reel
EIA 296
0251 xxxx N R T1
Lead Length
Type of Packaging
Quantity
Current Rating
Series
The default lead length for Ammo pack and
Loose pack is now T1 for 251 series, and
remains T3 for 253 series, therefore:
T1 = 52.4mm (2.062”), 251 series only*
Blank = 52.4mm (2.062”) for 251 series*
or 73mm (2.874”) for 253 series**
R = Reel
A = Ammo Pack
X = Loose Pack
N = 5000
P = 2000
M = 1000
H = 100
Refer to Amp Code column of
Electrical Specifications Table
251 = Standard type
253 = Military type
Option Codes
L
L = RoHS + HF
(Only applies to 251 Series)
The default lead length for both ammo pack and loose pack is T1 for 251 and is T3 for 253.
Notes: * T1 dimension is defined as the length of the component between the two
tapes. The full component length is 62.7mm (2.468"). T1 length is for 251 series only.
** T3 dimension is defined as the length of the component between the two
tapes. The full component length is 83.3.7mm (3.28”). T3 length is for 253 series only.
Wire Diameter:
0.64 (.025") for 0.62-10.0 amp,
0.81 (.032") for 15 amp
Wire Diameter:
0.64 (.025") for 0.62-10.0 amp,
0.81 (.032") for 12-15 amp
2.61 (.103")
MAX
6.35 (.25")
tape
5.0 (.197")
6.35 (.25")
tape
38.1
(1.5")
38.1
(1.5")
7.11 (.280")
83.31 (3.28")
253 Series Markings
(T3 lead length)
L
1 A
L
1 A
73.0 (2.874")**
L
1 A
F
L
1 A
27.78
(1.094")
27.78
(1.094")
7.11 (.280")
62.7 (2.468")
52.4 (2.062")*
2.80
(.11")
MAX
6.35 (.25")
tape
5.0 (.197")
6.35 (.25")
tape
251 Series (Halogen-free Version) Markings
(T1 lead length)
Wire Diameter:
0.64 (.025") for 0.62-10.0 amp,
0.81 (.032") for 12-15 amp
F
L
1 A
F
L
1 A
27.78
(1.094")
27.78
(1.094")
7.11 (.280")
62.7 (2.468")
52.4 (2.062")*
2.80
(.11")
MAX
6.35 (.25")
tape
5.0 (.197")
6.35 (.25")
tape
251 Series Markings
(T1 lead length)
F
F
F
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.