Revised: January 7, 2009
131
© 2009 Littelfuse, Inc.
Specifications 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 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.
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% 1/500–5 4 Hours, Min.
200% 1/500–3/10 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
I2t (A2 sec)
Agency Approvals
QP
L
.002 .002 125
10,000 amperes at
125 VAC/VDC.
2200 0.00000000845 XXX
.005 .005 125 280 0.00000000810 XXX
.010 .010 125 80.0 0.000000462 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 availablet
High breaking capacityt
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 componentst
Revised: January 7, 2009
Introduction to Circuit Protection
Introduction to Circuit Protection
Transientology
132 © 2009 Littelfuse, Inc.
Specifications 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
110 100
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 Time
0
20
40
60
80
100
120
140
160
180
200
220
240
260
280
300
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
210
220
230
240
Time (Seconds)
Temperature (°C) - Measured on bottom side of board
Cooling Time
Preheat Time
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 +/- 5°C
Heating Time: 5 seconds max.
Note: These devices are not recommended for IR or
Convection Reflow process.
Recommended Process Parameters:
Revised: January 7, 2009
133
© 2009 Littelfuse, Inc.
Specifications 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: –55ºC to +85ºC;
272 and 278: –55ºC 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 Specification Quantity Quantity &
Packaging Code
Bulk N / A 5 V
Bulk N / A 100 H
