Surface Mount Fuses
Thin Film > 0603 Size > Fast-Acting > 494 Series
494 Series Fuse, NRA Special Series Integrated Circuit Protector
Description
RoHS
Pb
®
The 494 Series Fast-Acting SMF is an ultra small (0603
size) thin-film device designed for secondary protection
of circuits used in space constrained applications such
as hand-held portable electronic devices. This series is
100% lead-free and meets the requirements of the RoHS
directive. New Halide-Free 494 Series fuses are available
to order using the “HF” suffix. See Part Numbering section
for additional information.
Features
Agency Approvals
Agency
®
Agency File number
e10480
lr29862
Ampere rAnge
250mA - 5A
250mA - 5A
• Compatible with lead-
free solders and higher
temperature profiles
• High performance
materials provide
improved performance
in elevated ambient
temperature applications
• Element-covering material
is resistant to industry
standard cleaning
operations
• Mounting pad and
electrical performance are
identical to Littelfuse 431
and 434 Series products
Electrical Characteristics for Series
% of Ampere
rating
100%
200%
300%
Opening Time at 25
O
c
4 hours, Minimum
5 sec., Maximum
0.2 sec., Maximum
• Marked on top surface
• Alloy-based element
with code to allow ampere construction provides
rating identification
superior inrush withstand
without testing
characteristics (I
2
t) over
ceramic or glass-based
• Low profile for height
0603 fuse products
sensitive applications
• Flat top surface for pick-
and-place operations
Applications
Secondary protection for space constrained applications:
• Cell phones
• Digital cameras
• DVD players
Additional Information
Datasheet
Resources
Samples
• Battery packs
• Hard disk
drives
Electrical Specifications by Item
Ampere
rating
(A)
0.250
0.375
0.500
0.750
1.00
1.25
1.40
1.50
1.75
2.00
2.50
3.00
3.15
3.50
4.00
5.00
Amp
code
.250
.375
.500
.750
001.
1.25
01.4
01.5
1.75
002.
02.5
003.
3.15
03.5
004.
005.
max
Voltage
rating
(V)
32
32
32
32
32
32
32
32
32
32
32
32
32
32
32
32
interrupting
rating
nominal cold
resistance
(Ohms)
0.5450
0.2900
0.1870
0.1170
0.0710
0.0530
0.049
0.0410
0.0320
0.0300
0.0220
0.0180
0.017
0.0150
0.0130
0.0090
nominal
melting
i
2
t (A
2
sec)
0.0030
0.0053
0.0087
0.0171
0.0212
0.0518
0.05529
0.0766
0.0903
0.1103
0.1440
0.2403
0.27405
0.4306
0.5760
0.9000
nom
Voltage
Drop
(mV)
158.56
128.03
115.71
107
.33
89.10
84.32
74.84
81.14
78.75
78.22
76.10
75.04
63.78
74.25
73.72
72.71
Agency Approvals
nom
power
Dissipation
®
(W)
0.0396
0.0480
0.0579
0.0805
0.0891
0.1054
0.1048
0.1217
0.1378
0.1564
0.1903
0.2251
0.2009
0.2599
0.2949
0.3635
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
50A @32V AC/DC
35A @32V AC/DC
1. Measured at 10% of rated current, 25ºC.
2. Measured at rated voltage.
© 2014 Littelfuse, Inc.
Specifications are subject to change without notice.
Revised: 10/25/14
Surface Mount Fuses
Thin Film > 0603 Size > Fast-Acting > 494 Series
Temperature Rerating Curve
Average Time Current Curves
0.250 A
0.375 A
0.500 A
0.750 A
1.00 A
1.25 A
1.50 A
100
10
TIME IN SECONDS
1
0.1
0.01
0.001
0.1
1
10
CURRENT IN AMPERES
1.75 A
2.00 A
2.50 A
3.00 A
3.50 A
4.00 A
5.00 A
100
Soldering Parameters
reflow condition
- Temperature min (T
s(min)
)
pre Heat
- Temperature max (T
s(max)
)
- Time (min to max) (t
s
)
Average ramp-up rate (liquidus Temp
(T
l
) to peak)
T
S(max)
to T
l
- ramp-up rate
reflow
- Temperature (T
l
) (liquidus)
- Temperature (t
l
)
Pb – free assembly
150°C
60 – 180 seconds
5°C/second max.
5°C/second max.
217°C
60 – 150 seconds
250
+0/-5
T
P
T
L
Temperature
t
P
Ramp-up
Critical Zone
T
L
to T
P
200°C
T
S(max)
T
S(min)
Preheat
t
L
Ramp-down
t
S
time to peak temperature
(t 25ºC to peak)
25
peak Temperature (T
p
)
Time within 5°c of actual peak
Temperature (t
p
)
ramp-down rate
Time 25°c to peak Temperature (T
p
)
Do not exceed
°C
Time
20 – 40 seconds
5°C/second max.
8 minutes max.
260°C
© 2014 Littelfuse, Inc.
Specifications are subject to change without notice.
Revised: 10/25/14
Surface Mount Fuses
Thin Film > 0603 Size > Fast-Acting > 494 Series
Product Characteristics
Body:
Advanced High Temperature Substrate
Terminations: 100% Tin over Nickel over Copper
Element Cover Coat:
Conformal Coating
– 55°C to 90°C. Consult temperature rerating
curve chart. For operation above 90°C contact
Littelfuse.
MIL-STD-202F
, Method 103B, Condition D
Thermal Shock
Vibration
Insulation Resistance
(After Opening)
Resistance to
Soldering Heat
Withstands 5 cycles of – 55°C to 125°C
Per MIL
-STD-202F
Greater than 10,000 ohms
Withstands 60 seconds above 200°C
and up to 260°C, maximum
Materials
Operating
Temperature
Humidity
Dimensions
1.60
(.063")
.127
(.005")
Sn
Coating
Part Marking System
.305
(.012")
Amp
code
.250
.375
.500
.750
001.
1.25
01.4
01.5
1.75
002.
02.5
003.
3.15
03.5
004.
005.
marking
code
D
E
F
G
H
J
K
L
N
O
P
R
S
T
Sn
Cu
MARKING CODE VARIES
WITH AMPERAGE RATING
(SEE CHART)
R
(.007")
REF.
Sn
.279
(.011")
.18
.813
(.032")
1.09
(.043")
1.02
(.040")
3.20
(.126")
2.54
(.100")
1.02
(.040")
.762
(.030")
1.09
(.043")
WAVE SOLDER
1.09
(.043")
REFLOW SOLDER
Packaging
packaging
Option
8mm Tape
and Reel
packaging
Specification
EIA RS-481-2 (IEC
286, part 3)
Quantity
Quantity &
packaging
code
NR
Part Numbering System
0494002.NRHF
SERIES
AMP Code
Refer to Amp Code column in the
Electrical Specifications table.
NOTE: The dot is poisitioned before
the Packaging Suffix with whole
ratings and within the numbering
sequence for fractional ratings.
5000
PACKAGING Code
NR = Tape and Reel, 5000 pcs
‘HF’ SUFFIX HALIDE
FREE ITEM
© 2014 Littelfuse, Inc.
Specifications are subject to change without notice.
Revised: 10/25/14
