Surface Mount Fuses
®
®
®
Thin Film > 0603 Size > Fast-Acting > 494 Series
494 Series Fuse, NRA Special Series Integrated Circuit Protector
Description
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 AMPERE RANGE
E10480 250mA - 5A
LR29862 250mA - 5A
Electrical Characteristics for Series
% of Ampere
Rating
100% 4 hours, Minimum
200% 5 sec., Maximum
300% 0.2 sec., Maximum
Opening Time at 25
O
C
Additional Information
Datasheet
Resources
Samples
• Compatiblewithlead-
free solders and higher
temperature profiles
• Highperformance
materials provide
improved performance
in elevated ambient
temperature applications
• Markedontopsurface
with code to allow ampere
rating identification
without testing
• Lowproleforheight
sensitive applications
• Flattopsurfaceforpick-
and-place operations
Applications
Secondary protection for space constrained applications:
• Cellphones
• Batterypacks
• Element-coveringmaterial
is resistant to industry
standard cleaning
operations
• Mountingpadand
electrical performance are
identical to Littelfuse 431
and 434 Series products
• Alloy-basedelement
construction provides
superior inrush withstand
characteristics (I
ceramic or glass-based
0603 fuse products
• Digitalcameras
• DVDplayers
2
t) over
• Harddisk
drives
Electrical Specifications by Item
Ampere
Rating
(A)
0.250 .250 32
0.375 .375 32 0.2900 0.0053 128.03 0.0480 x x
0.500 .500 32 0.1870 0.0087 115.71 0.0579 x x
0.750 .750 32 0.1170 0.0171 107.33 0.0805 x x
1. 0 0 0 01. 32 0.0710 0.0212 89.10 0.0891 x x
1.25 1.25 32
1.50 01.5 32 0.0410 0.0766 81.14 0.1217 x x
1.75 1.75 32 0.0320 0.0903 78.75 0.1378 x x
2.00 002. 32 0.0300 0.1103 78.22 0.1564 x x
2.50 02.5 32 0.0220 0.1440 76.10 0.1903 x x
3.00 003. 32 0.0180 0.2403 75.04 0.2251 x x
3.50 03.5 32 0.0150 0.4306 74.25 0.2599 x x
4.00 004. 32 0.0130 0.5760 73.72 0.2949 x x
5.00 005. 32 0.0090 0.9000 72.71 0.3635 x x
1. Measured at 10% of rated current, 25ºC. 2. Measured at rated voltage.
Amp
Code
Max
Voltage
Rating
(V)
Interrupting
Rating
50A @32V AC/DC
35A @32V AC/DC
Nominal Cold
Resistance
(Ohms)
0.5450 0.0030 158.56 0.0396 x x
0.0530 0.0518 84.32 0.1054 x x
Nominal
Melting
2
t (A2sec)
I
Nom
Voltage
Drop
(mV)
Nom
Power
Dissipation
(W)
Specifications are subject to change without notice.
Agency Approvals
© 2013 Littelfuse, Inc.
Revised: 12/19/13
Surface Mount Fuses
0
0.00
A
A
A
A
Thin Film > 0603 Size > Fast-Acting > 494 Series
Temperature Rerating Curve
Average Time Current Curves
1.50 A
1.25 A
0.500
0.375
100
10
TIME IN SECONDS
0.1
0.01
0.250
1
1
0.1
1.00 A
0.750
1
CURRENT IN AMPERES
3.50 A
3.00 A
2.50 A
2.00 A
1.75 A
10 10
5.00 A
4.00 A
Soldering Parameters
Reflow Condition Pb – free assembly
- Temperature Min (T
Pre Heat
- Temperature Max (T
- Time (Min to Max) (ts) 60 – 180 seconds
Average Ramp-up Rate (Liquidus Temp
(T
) to peak)
L
to TL - Ramp-up Rate 5°C/second max.
T
S(max)
Reflow
- Temperature (TL) (Liquidus) 217°C
- Temperature (tL) 60 – 150 seconds
Peak Temperature (TP) 250
Time within 5°C of actual peak
Temperature (t
)
p
) 150°C
s(min)
) 200°C
s(max)
5°C/second max.
+0/-5
°C
20 – 40 seconds
T
Temperature
S(max)
T
S(min)
T
P
T
L
25
time to peak temperature
Preheat
t
S
(t 25ºC to peak)
Ramp-up
Ramp-down Rate 5°C/second max.
Time 25°C to peak Temperature (T
) 8 minutes max.
P
Do not exceed 260°C
t
P
Critical Zone
T
to T
L
P
t
L
Ramp-down
Time
© 2013 Littelfuse, Inc.
Specifications are subject to change without notice.
Revised: 12/19/13
Product Characteristics
1.60
(.032")
Surface Mount Fuses
Thin Film > 0603 Size > Fast-Acting > 494 Series
Body: Advanced High Temperature Substrate
Materials
Terminations: 100% Tin over Nickel over Copper
Element Cover Coat: Conformal Coating
Operating
Temperature
– 55°C to 90°C. Consult temperature rerating
curve chart. For operation above 90°C contact
Littelfuse.
Humidity MIL-STD-202F, Method 103B, Condition D
Thermal Shock Withstands 5 cycles of – 55°C to 125°C
Vibration Per MIL-STD-202F
Insulation Resistance
(After Opening)
Resistance to
Soldering Heat
Dimensions Part Marking System
Sn
.813
(.063")
.127
(.005")
MARKING CODE VARIES
WITH AMPERAGE RATING
(SEE CHART)
Cu
1.09
(.043")
1.02
(.040")
1.09
(.043")
WAVE SOLDER
Sn
3.20
(.126")
Sn
R
REF.
.18
(.007")
(.012")
1.09
(.043")
Coating
.279
(.011")
2.54
(.100")
REFLOW SOLDER
.305
1.02
(.040")
.762
(.030")
Amp
Code
.250 D
.375 E
.500 F
.750 G
0 01. H
1.25 J
01.5 K
1.75 L
002. N
02.5 O
003. P
03.5 R
004. S
005. T
Part Numbering System
Marking
Code
0494002.NRHF
Greater than 10,000 ohms
Withstands 60 seconds above 200°C
and up to 260°C, maximum
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.
PACKAGING Code
NR = Tape and Reel, 5000 pcs
‘HF’ SUFFIX HALIDE
FREE ITEM
Packaging
Packaging Option Packaging Specification Quantity
8mm Tape and Reel EIA RS-481-2 (IEC 286, part 3) 5000 NR
Packaging Code
Quantity &
Specifications are subject to change without notice.
© 2013 Littelfuse, Inc.
Revised: 12/19/13
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