Radial Lead Fuses
L
L
MICRO™ > Very Fast-Acting > 272/273/274/278/279 Series
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 plug–in or radial lead
styles and a complete range of ampere ratings from
1/500 to 5A to suit a wide variety of design needs.
Features
Military grade availablet
High breaking capacityt
Clear cover option to view t
Agency Approvals
Agency Agency File Number Ampere Range
E10480 2mA - 5A
LR 29862 2mA - 5A
QP
FM02 2mA - 5A
fuse element status
Applications
Printed circuit boards t
and similar equipment
Electrical Characteristics
% of Ampere
Rating
100% 1/500–5 4 Hours, Min.
200%
Ampere Rating Opening Time
QPL
Available from very low t
ampere of 2mA to 5A
Plug-in with short or long t
leads option
Electronic componentst
1/500–3/10 5 Seconds, Max.
4/10-5 2 Seconds, Max.
272-4/278-9
Electrical Characteristics
Ampere
Rating
(A)
.002 .002 125
.005 .005 125 280 0.00000000810
.010 .010 125 80.0 0.000000462
.015 .015 125 44.0 0.00000123
.031 .031 125 16.0 0.00000810
.050 .050 125 3.20 0.0000666
.062 .062 125 2.32 0.000115
.100 .100 125 1.25 0.000385
.125 .125 125 1.0 0.000691
.200 .200 125 2.30 0.00409
.250 .250 125 1.75 0.00640
.300 .300 125 1.25 0.00945
.400 .400 125 0.227 0.0251
.500 .500 125 0.167 0.0716
.600 .600 125 0.430 0.0411
.700 .700 125 0.324 0.0710
.750 .750 125 0.293 0.0900
.800 .800 125 0.271 0.113
1.00 001. 125 0.0880 0.0648
01.5 01.5 125 0.0578 0.160
2.00 002. 125 0.0425 0.300
3.00 003. 125 0.0275 0.759
4.00 004. 125 0.0202 1.38
5.00 005. 125 0.0156 2.21
Amp Code
(for all
above
series)
Max
Voltage
Rating
(V)
Interrupting
Rating
10,000 amperes at
125 VAC/VDC.
Nominal
Cold
Resistance
(Ohms)
2200 0.00000000845
Nominal
Melting
2
I
t (A2 sec)
Agency Approvals
QP
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
XXX
© 2009 Littelfuse, Inc.
Specifications are subject to change without notice.
Please refer to www.littelfuse.com/series/272.html, /273.html, /274.html,
/278.html or /279.html for current information.
131
Revised: January 7, 2009
272/273/274/278/279 Series
Introduction to Circuit Protection
Introduction to Circuit Protection
MICRO™ > Very Fast-Acting > 272/273/274/278/279 Series
Radial Lead Fuses
Transientology
Temperature Rerating Curve
Average Time Current Curves
1/64 A
1/100 A
1/200 A
100
10
1
TIME IN SECONDS
0.1
0.01
0.001
0.005
0.01
1/32 A
1/16 A
1/8 A
1/4 A
0.1
CURRENT IN AMPERES
1/2 A
1
3/4 A
1 A
1 1/2 A
2 A
3 A
4 A
5 A
10
100
Soldering Parameters - Wave Soldering
300
280
260
240
220
200
180
160
140
120
100
80
60
40
20
0
Temperature (°C) - Measured on bottom side of board
0
102030405060708090
Time (Seconds)
Preheat Time
100
110
120
130
140
150
Dwell Time
160
170
Cooling Time
Recommended Process Parameters:
Wave Parameter Lead-Free Recommendation
Preheat:
(Depends on Flux Activation Temperature)
Temperature Minimum:
Temperature Maximum:
(Typical Industry Recommendation)
100
° C
150
° C
Preheat Time: 60-180 seconds
Solder Pot Temperature:
260
° C Maximum
Solder Dwell Time: 2-5 seconds
180
190
200
210
220
Recommended Hand-Solder Parameters:
230
240
Solder Iron Temperature: 350° C +/- 5°C
Heating Time: 5 seconds max.
Note: These devices are not recommended for IR or
Convection Reflow process.
272/273/274/278/279 Series
132
Revised: January 7, 2009
© 2009 Littelfuse, Inc.
Please refer to www.littelfuse.com/series/272.html, /273.html, /274.html,
Specifications are subject to change without notice.
/278.html or /279.html for current information.
Radial Lead Fuses
MICRO™ > Very Fast-Acting > 272/273/274/278/279 Series
Product Characteristics
Operating Temperature:
Fuses to MIL SPEC
Materials
Product Marking
Part Numbering System
0273 xxxx V
Series
Amp. Code
Refer to Amp Code column of
Electrical Characteristics Table
Packaging Code
V = 5
H = 100
273 and 279: –55ºC to +85ºC;
272 and 278: –55ºC to +125ºC
273 Series is available in CSA LR
29862. Military QPL type (FM02).
To order, change 273 to 274.
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
Current and voltage ratings stamped
on cap
Dimensions
272 000 Series
(Short Lead, Metal Cap)
5.97
(.235")
7.30
(.29")
4.32
(.17")
2.54 (.10")
278 000 Series
(Long Lead, Metal Cap)
5.97
(.235")
7.30
(.29")
25.4 (1.0")
273 000 and 274 000 Series
(Short Lead, Clear Plastic Cap)
6.35
(.25")
8.89
(.35")
4.32
(.17")
2.54 (.10")
279 000 Series
(Long Lead, Clear Plastic Cap)
6.35
(.25")
8.89
(.35")
25.4 (1.0")
2.54 (.10")
2.54 (.10")
272-4/278-9
Packaging
Packaging Option Packaging Specification Quantity
Bulk N / A 5 V
Bulk N / A 100 H
NOTE: Amperage and voltage rating stamped on cap.
Leads are tin plated copper; .025" diameter.
Quantity &
Packaging Code
© 2009 Littelfuse, Inc.
Specifications are subject to change without notice.
Please refer to www.littelfuse.com/series/272.html, /273.html, /274.html,
/278.html or /279.html for current information.
133
Revised: January 7, 2009
272/273/274/278/279 Series
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