Surface-mount Fuses
– Fundamentals
Surface-mount Fuses
Fundamentals
Overview
TE Circuit Protection offers the widest selection of surface-mount
fuses available for addressing a broad range of overcurrent
protection applications. Helping to prevent costly damage and
promote a safe environment for electronic and electrical
equipment, our single-use chip fuses provide performance stability
to support applications with current ratings from .5A up to 20A.
TE Circuit Protection also offers the telecom FT600 fuse for
telecommunications applications. This telecom fuse helps comply
with North American overcurrent protection requirements,
including Telcordia, GR-1089, TIA-968-A (formerly FCC Part 68),
and UL60950 3rd edition.
Multi-layer Design for Chip Fuses
The multi-layer design has the benefit of exposing more fuse
element surface area to the glass-ceramic absorption material.
When the fuse elements open, there is more material for the
vaporizing fuse metals to absorb into, resulting in a very efficient
and effective quenching of the fuse arc.
Figure 1 compared the multi-layer design of our SFF fuses with
standard glass coated designs. The glass coated designs rely on
the coating on only one side of the fuse element to absorb the
vaporizing fuse material when it opens. Therefore, there is much
less absorption material available to absorb the fuse metals. The
result can be prolonged arcing and possible coating breach.
Figure 2 shows how the absorption characteristics of the two
designs differ. The multi-layer design indicates a clean separation
with the fuse element evenly diffusing into the surrounding
ceramic substrate. In the glass coated design, the element
diffusion takes place in a small portion of the device and is only
absorbed by the glass material directly above the area of failure.
Figure 1
Glass/Ceramic
Substrate
Multiple Fuse
Elements
Substrate
Material
Single Fuse Glass
Element Coating
Multi-layer Design
Single-layer Glass Coated Design
Figure 2
Fault Zones
11
Multi-layer Design
Single-layer Glass Coated Design
Wire-In-Air Design for 2410SFV Fuses
The 2410(6125) is a Wire-In-Air SMD Fuse which is very suitable
for secondary level over current protection applications.
Figure 3 compared our straight wire element design 2410SFV
fuses with normal corrugating wire design fuse. The straight wire
element in air performs consistent fusing and cutting
characteristics together with excellent inrush current
withstanding capability.
Introduced PCB assembly technology into 2410SFV fuses design
and manufacture, we achieved on lead free completely and no
end cap falling off risk comparing with traditional ceramic body
with end cap fuse.
Figure 3
Glass fiber enforced
epoxy body
Straight wire element
Copper terminal
plated with Ni and Tin
Ceramic body
Corrugate wire element
End cap plated with Tin
75
Temperature Derating
A fuse is a temperature sensitive device. Therefore, operating temperature will have an effect on fuse performance and lifetime.
Operating temperature should be taken into consideration when selecting the fuse current rating. The Thermal Derating Curve for
surface mount fuses is presented in Figure 4. Use it to determine the derating percentage based on operating temperature and
apply it to the derated system current.
Figure 4
1206/0603/0402 Series
Temperature Effect on Current Rating
105
100
95
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
-55
110
105
100
95
2410 Series
Temperature Effect On Current Rating
% De-rating
% De-rating
-35
-15
5
25
45
65
85
105
125
145
90
85
80
75
70
65
60
55
50
-55
-35
-15
5
25
45
65
85
105
125
Maximum Operating Temperature (°C)
Maximum Operating Temperature (°C)
Pulse Cycle Derating
Once the I
2
t value for the application waveform has been
determined, it must be derated based on the number of cycles
expected over the system lifetime. Since the stress induced by the
current pulse is mechanical in nature, the number of times the
stress is applied has significant bearing on how much derating
must be applied to the fuse rating. Figure 5 presents the current
pulse derating curve for our surface-mount chip fuses up to
100,000 cycles.
Figure 5
Surface-mount Fuse Pulse Derating Curve
100%
% of Minimum I
2
t
10%
100
1000
10000
100000
Number of Pulses
Selecting Surface-mount Fuses
11
Fuse selection seems straightforward, in that, you pick one which has a current rating just a bit higher than your worstcase system
operating current. Unfortunately, it’s not that simple. There are derating considerations for operating current and application
temperature. Turn-on and other system operations (like processor speed changes or motor start up) cause current surges or
spikes that also require consideration when selecting a fuse. So selecting the right fuse for your application is not as simple as
knowing the nominal current drawn by the system.
Fuse Selection Flowchart
However, the basic considerations for fuse selection are shown in the flowchart presented in Figure 6. Following this flow chart
will help you select a fuse best suited for your application conditions.
Figure 6
Step 1 –
Determine Steady State
Fuse Current Rating
Apply Standard Steady
State Derating (75%)
[I
fuse
≥
I
sys
/0.75]
Apply
Temperature Derating
[I
fuse
≥
I
sys
/0.75/K
temp
]
Steady State
Fuse Current
Rating
Step 2 –
Determine Pulse
Waveform by
Calculating I
2
t
Step 3 –
Apply Pulse
Cycle Derating
Step 4 –
Apply Pulse
Temperature
Derating
Step 5 –
Apply Derating
for Variance in
the Circuit
Step 6 –
Select Fuse Current
Rating for Pulse
Environment
Step 7 –
Select Fuse Current Rating
(use higher value between Step 1 and Step 6)
Step 8 –
Check Voltage Rating
76
Surface-mount Fuses
– Pulse Tolerant Chip Fuses
Surface-mount Fuses
Pulse Tolerant Chip Fuses
Pulse Tolerant chip fuses has high inrush current
withstand capability and provide overcurrent protection
on DC power systems. Silver fusing element, monolithic
and multilayer design provides strong arc suppression
characteristics.
These RoHS-compliant surface-mount devices facilitate
the development of more reliable, high performance
consumer electronics such as laptops, multimedia
devices, cell phones, and other portable electronics.
NE
W
Benefits
• High inrush current withstanding capability
• Ceramic Monolithic structure
• Silver fusing element and silver termination with
nickel and tin plating
• Excellent temperature stability
• Strong arc suppression characteristics
Features
• Lead free materials and RoHS compliant
• Halogen free
(refers to: Br 900ppm, Cl 900ppm, Br+Cl 1500ppm)
• Monolithic, multilayer design
• High-temperature performance
• -55°C to +125°C operating temperature range
11
Applications
• Laptops
• Digital cameras
• Cell phones
• Printers
• DVD players
• Portable electronics
• Game systems
• LCD monitors
• Scanners
77
Table FP1 Clear Time Characteristics for Pulse Tolerant Chip Fuses
% of rated current
100%
200%
1000%
Clear time at 25°C
4 hours (min.)
1 seconds (min.)
0.0002 second (min.)
60 seconds (max.)
0.02 seconds (max.)
Table FP2 Typical Electrical Characteristics and Dimensions for Pulse Tolerant Chip Fuses
0603 (1608 mm) Pulse Tolerant Chip Fuses
Typical
Electrical Characteristics
D
A
Max.
Interrupt Ratings
Voltage
(V
DC
)
32
32
32
32
32
32
32
32
32
Current
(A)
50
50
50
50
50
50
50
50
50
Shape and Dimensions
mm (Inch)
B
Part Number
0603SFP100F/32-2
0603SFP150F/32-2
C
Rated
Current
(A)
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Nominal Nominal
I
2
t
Cold DCR
2
sec)
†
(A
(Ω)*
0.210
0.101
0.057
0.042
0.030
0.022
0.018
0.014
0.013
0.080
0.11
0.24
0.56
0.72
1.10
2.08
2.63
3.25
0603SFP200F/32-2
0603SFP250F/32-2
C
D
Max
0.51
Min
0.65
Max
0.95
A
Min
mm
in
1.45
Max
1.75
Min
0.65
B
Max
0.95
Min
0.21
0603SFP300F/32-2
0603SFP350F/32-2
0603SFP400F/32-2
0603SFP450F/32-2
0603SFP500F/32-2
(0.057) (0.069)
(0.026) (0.037)
(0.008) (0.020)
(0.026) (0.037)
1206 (3216 mm) Pulse Tolerant Chip Fuses
Typical
Electrical Characteristics
D
A
Max.
Interrupt Ratings
Voltage
(V
DC
)
63
63
63
32
32
32
32
32
32
Current
(A)
50
50
50
50
50
50
50
50
50
11
Shape and Dimensions
mm (Inch)
B
Part Number
1206SFP100F/63-2
1206SFP150F/63-2
1206SFP200F/63-2
1206SFP250F/32-2
C
Rated
Current
(A)
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Nominal Nominal
I
2
t
Cold DCR
2
sec)
†
(A
(Ω)*
0.340
0.150
0.090
0.070
0.035
0.029
0.023
0.021
0.017
0.11
0.33
0.80
1.19
1.35
1.84
2.74
3.20
5.50
1206SFP300F/32-2
D
1206SFP350F/32-2
Max
1.80
1206SFP400F/32-2
1206SFP450F/32-2
1206SFP500F/32-2
Min
1.40
A
Min
mm
in
3.00
Max
3.40
Min
0.77
B
Max
1.17
Min
0.26
C
Max
0.76
(0.118) (0.134)
(0.030) (0.046)
(0.010) (0.030)
(0.055) (0.071)
* Measured at 10% of rated current and 25°C ambient temperature.
† Melting I
2
t at 0.001 sec clear time.
78
RoHS Compliant, ELV Compliant
HF
Halogen Free
Surface-mount Fuses
– Pulse Tolerant Chip Fuses
Figure FP1-FP4 Family Performance Curves for Pulse Tolerant Chip Fuses
Figure FP1
0603SFP Average Time Current Curves
1.5
A
1.0
A
100
10
1
Clear Time (s)
0.1
0.01
0.001
0.0001
1
10
100
2. 0
2. 5
3.0
Current (A)
Figure FP2
0603SFP I
2
T vs. t Curves
10,000
5.0A
4.5A
4.0A
3.5A
3.0A
2.5A
2.0A
1.5A
1.0A
100
4.0
4.5
A
5.0
A
A
A
A
3.5
A
A
1000
11
I
2
t (A
2
s)
10
1
0.1
0.01
0.0001
0.001
0.01
0.1
1
10
100
Time (s)
Note:
Curves are nominal
RoHS Compliant, ELV Compliant
HF
Halogen Free
79
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