Surface Mount Fuses
Ceramic Fuse > 437 Series
437 Series – 1206 Fast-Acting Fuse
Description
This 100% Lead-free, RoHS compliant and Halogen-free
fuse series has been designed specifically to provide over
current protection to circuits that see high working ambient
temperatures (up to 150ºC).
The general design ensures excellent temperature stability
and performance reliability.
In addition to this, the high I²t values typical of the
Littelfuse Ceramic Fuse family ensure high inrush current
withstand capability.
Agency Approvals
AGENCY
AGENCY FILE NUMBER
E10480
LR29862
AMPERE RANGE
0.250A ~ 8A
0.250A ~ 8A
Features
from -55ºC to +150ºC
RoHS compliant
Applications
and lead-free reflow /
wave soldering
Electrical Characteristics for Series
% of Ampere
Rating
100%
250%
350%
350%
Ampere Rating
250mA - 8A
750mA - 8A
250mA -500mA
750mA - 8A
Opening Time at 25ºC
4 hours, Minimum
5 seconds, Maximum
5 seconds, Maximum
1 second, Maximum
Electrical Specifications by Item
Ampere
Max.
Amp
Rating
Voltage
Code
(A)
Rating (V)
250mA
375mA
500mA
750mA
1A
1.25A
1.5A
1.75A
2A
2.5A
3A
3.5A
4A
5A
7A
8A
.250
.375
.500
.750
001.
1.25
01.5
1.75
002.
02.5
003.
03.5
004.
005.
007
.
008.
125
125
63
63
63
63
63
63
63
32
32
32
32
32
32
32
Interrupting Rating
50 A @ 125 V AC/DC
Nominal Nominal Voltage Nominal Power Agency Approvals
Nominal
Drop At Rated
Dissipation At
Resistance Melting I
2
t
(A
2
Sec.)
3
Current (V)
4
Rated Current (W)
(Ohms)
2
2.290
1.330
0.908
0.665
0.360
0.318
0.209
0.0703
0.058
0.043
0.033
0.027
0.022
0.016
0.010
0.0084
0.003
0.010
0.018
0.064
0.100
0.256
0.324
0.075
0.144
0.225
0.400
0.576
1.024
1.936
4.900
6.400
0.78
0.60
0.52
0.45
0.41
0.40
0.39
0.27
0.17
0.14
0.15
0.16
0.16
0.09
0.11
0.067
0.195
0.225
0.260
0.335
0.415
0.496
0.579
0.474
0.345
0.363
0.462
0.560
0.618
0.484
0.760
0.539
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
50 A @ 63 V AC/DC
50 A @ 32 V AC/DC
Notes:
1. AC Interrupting Rating tested at rated voltage with unity power factor. DC Interrupting
Rating tested at rated voltage with time constant < 0.8 msec.
2. Nominal Resistance measured with < 10% rated current.
3. Nominal Melting I²t measured at 1 msecs. opening time.
4. Nominal Voltage Drop measured at rated current after temperature has stabilized.
© 2009 Littelfuse, Inc.
Specifications are subject to change without notice.
Please refer to www.littelfuse.com/series/437.html for current information.
17
Devices designed to carry rated current for 4 hours minimum. It is recommended that
devices be operated continuously at no more than 80% rated current. See “Temperature
Rerating Curve”for additional rerating information.
Devices designed to be mounted with marking code facing up.
437 Series
Revised: August 3, 2009
Surface Mount Fuses
Introduction to Circuit Protection
Transientology
Ceramic Fuse > 437 Series
Temperature Rerating Curve
Average Time Current Curves
.375A
.500A
.250A
.750A
1A
1.25
1.5A
1.75
2A
2.5A
3A
3.5A
4A
5A
140
100
PERCENT OF RATING
120
100
10
80
TIME IN SECONDS
60
1
40
-65
-45
-25
-5
15
35
55
75
95
115
135
155
TEMPERATURE (°C)
0.1
Note:
1. Rerating depicted in this curve is in addition to the standard rerating of 20% for
continuous operation.
0.01
For continuous operation at 75 degrees celsius, the fuse should be rerated as follows:
I = (0.80)(0.85)I
RAT
= (0.68)I
RAT
0.001
0.1
1
10
100
CURRENT IN AMPERES
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
)
260
+0/-5
T
P
150°C
Ramp-up
7A
8A
t
P
Critical Zone
T
L
to T
P
Temperature
200°C
T
L
T
S(max)
Preheat
t
L
Ramp-down
3°C/second max.
5°C/second max.
217°C
°C
T
S(min)
t
S
25
time to peak temperature
(t 25ºC to peak)
Time
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
6°C/second max.
8 minutes max.
260°C
Wave Soldering
260°C, 10 seconds max.
437 Series
18
© 2009 Littelfuse, Inc.
Specifications are subject to change without notice.
Please refer to www.littelfuse.com/series/437.html for current information.
Surface Mount Fuses
Ceramic Fuse > 437 Series
Product Characteristics
Body:
Advanced Ceramic
Terminations:
Ag / Ni / Sn (100% Lead-free)
Element Cover Coating:
Lead-free Glass
Moisture Resistance
Thermal Shock
Mechanical Shock
Vibration
Vibration,
High Frequency
Dissolution of
Metallization
Terminal Strength
MIL
-STD-202, Method 106G
MIL
-STD-202, Method 107G,
Materials
Moisture
Sensitivity Level
Solderability
Humidity Test
ESD Immunity
Resistance to
Solder Heat
Condition A
MIL
-STD-202, Method 201A
MIL
-STD-202, Method 204D,
Condition D
Condition D
Dimensions
1.000
[0.039]
3.200 ± 0.1778
[0.126 ± 0.007]
Part Marking System
Amp Code
.250
.375
.500
.750
001.
1.25
01.5
1.75
0.8179 +0.046 / -0.076
[0.0332 +0.0018 / -0.003]
Marking Code
D
E
F
G
H
J
K
L
N
O
P
R
S
T
W
X
1.63 +0.10 / -0.2
[0.064 +0.004 / -0.008]
N
2
002.
02.5
003.
03.5
004.
005.
007
.
008.
0.520 ± 0.200
[0.020 ± 0.08]
1.000
[0.039]
1.500
[0.059]
Part Numbering System
0437 008. W R
1.800
[0.071]
SERIES
PACKING CODE
AMP CODE
QUANTITY CODE
W = 3000 pcs
3.500
[0.138]
Packaging
Packaging Option
8mm Tape and Reel
© 2009 Littelfuse, Inc.
Specifications are subject to change without notice.
Please refer to www.littelfuse.com/series/437.html for current information.
Packaging Specification
Quantity
3000
Quantity &
Packaging Code
WR
437 Series
19
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