Varistor Products
Surface Mount Varistors > SM7 Series
SM7 Varistor Series
Agency Approvals
Agency Agency File Number
E320116
RoHS
Description
The Littelfuse SM7 Series is a plastic-encapsulated
surface-mount metal oxide varistor (MOV) transient
voltage surge suppressor that is designed to be
operated continuously across AC power lines.
The series comprises a Nylon molded package with
tin plated lead frame for soldering to board. The
surface mount SM7 Series is based on radial 7mm
internal varistor element with similar characteristics
to the Littelfuse LA / ZA series of varistor.
Features
• Electrical equivalent
to leaded types
LA/ZA series
• AC Voltage Rating
115 to 510VAC rms
• Good solderability
• Available in tape
and reel
• Application of AC
power meters
• No De-Rating up
to 85°C ambient
SM7 Series
Absolute Maximum Ratings
• For ratings of individual members of a series, see Device Ratings and Specifications chart
Continuous
Steady State Applied Voltage:
AC Voltage Range (V
DC Voltage Range (V
) 115 to 510 V
M(AC)RMS
) 153 to 675 V
M(DC)
Transients:
Peak Pulse Current (ITM)
For 8/20μs Current Wave (See Figure 2) 1200 A
Single Pulse Energy Range
For 10/1000μs Current Wave (W
Operating Ambient Temperature Range (T
Storage Temperature Range (T
Temperature Coefficient (a
Hi-Pot Encapsulation (COATING Isolation Voltage Capability)
(Dielectric must withstand indicated DC voltage for one minute per MIL-STD 202, Method 301)
COATING Insulation Resistance 1000 MΩ
STG
V
) of Clamping Voltage (VC) at Specified Test Current <0.01 %/OC
) -40 to +85
A
) -55 to +125
) 10 to 40 J
TM
CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only
rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is
not implied.
SM7 Series Units
O
C
O
C
2500 V
© 2013 Littelfuse, Inc.
Specifications are subject to change without notice.
Please refer to www.littelfuse.com/series/sm7.html for current information.
75
Revised: May 8, 2013
SM7 Series Varistor
Varistor Products
Surface Mount Varistors > SM7 Series
SM7 Series Ratings & Specifications
Maximum Rating (85°C) Specifications (25°C)
Maximum
Clamping
Voltage
8 x 20 μs
IPK C
C
Capacitance
Part
Number
Continuous Transient
V
RMS
V
M(AC)
V
V
M(DC)
DC
Energy
10 x 1000μs
WTM I
Peak Current
8 x 20μs
V
TM
(V) (V) (J) (A) (V) (V) (V) (A) (pF)
Varistor Voltage
at 1mA DC
Test Current
Min V
NOM
NOM
Max V
V115SM7 115 153 10 1200 162 198 300 10 200
V130SM7 130 175 11 1200 184 228 340 10 180
V140SM7 140 180 12 1200 198 242 360 10 160
V150SM7 150 200 13 1200 212 268 395 10 150
V175SM7 175 225 15 1200 247 303 455 10 130
V230SM7 230 300 20 1200 324 396 595 10 100
V250SM7 250 330 21 1200 354 429 650 10 90
V275SM7 275 369 23 1200 389 473 710 10 80
V300SM7 300 405 25 1200 420 517 775 10 70
V320SM7 320 420 25 1200 462 565 850 10 65
V385SM7 385 505 27 1200 558 682 1025 10 60
V420SM7 420 560 30 1200 610 748 1120 10 55
V460SM7 460 615 37 1200 640 790 1190 10 55
V480SM7 480 640 35 1200 670 825 1240 10 50
V510SM7 510 675 40 1200 735 910 1200 10 45
NOTE: SM7 series devices are recognized under UL file # E320116
Typical
f = 1MHz
SM7 Series Varistor
76
Revised: May 8, 2013
Please refer to www.littelfuse.com/series/sm7.html for current information.
Specifications are subject to change without notice.
© 2013 Littelfuse, Inc.
Varistor Products
Surface Mount Varistors > SM7 Series
For applications exceeding 85ºC ambient temperature, the peak
surge current and energy ratings must be reduced as shown below
100
90
80
70
60
50
40
30
20
PERCENT OF RATED VALUE
10
0
-55 50 60 70 80 90 100 110 120 130 140 150
AMBIENT TEMPERATURE (
V-I Limit Curves
o
C)
Peak Pulse Current Test Waveform for Clamping VoltagePeak Current, Energy and Power Derating Curve
100
50
PERCENT OF PEAK VALUE Test
0
O
1
01 = Virtual Origin of Wave
T = Time from 10% to 90% of Peak
T1 = Rise Time = 1.25 x T
T2 = Decay Time
Example - For an 8/20 μs Current Waveform:
t
t
1
8μs = T1 = Rise Time
20μs = T2 = Decay Time
TIM E
SM7 Series
2000
1500
1000
Voltage(V)
500
0
0.001 0.01 0.1 1 10 100 1000
V510SM7
V480SM7
V460SM7
V420SM7
V385SM7
V320SM7
V300SM7
V250SM7
V230SM7
V210SM7
V190SM7
V175SM7
V150SM7
V140SM7
V130SM7
V115SM7
Current(A)
NOTE: If pulse ratings are exceeded, a shift of V
±10% could result. This type of shift, which normally results in a decrease of
result in the device not meeting the original published specifications, but it does not prevent
the device from continuing to function, and to provide ample protection.
(at specified current) of more than
N(DC)
V
N(DC)
, may
Pulse Rating Curves
10000
1
1000
2
10
2
10
100
3
10
Surge Current (A )
10
1
10 100 1000 10000
4
10
5
10
6
10
Impulse Duration (μs)
© 2013 Littelfuse, Inc.
Specifications are subject to change without notice.
Please refer to www.littelfuse.com/series/sm7.html for current information.
77
Revised: May 8, 2013
SM7 Series Varistor
Varistor Products
Surface Mount Varistors > SM7 Series
Lead (Pb) Soldering Recommendations
The principal techniques used for the soldering of
components in surface mount technology are IR Re-flow
and Wave soldering. Typical profiles are shown on the right.
The terminals of SM7 series devices are tin plated copper,
and the recommended solder is 62/36/2 (Sn/Pb/Ag), 60/40
(Sn/Pb) or 63/37 (Sn/Pb). Littelfuse also recommends an
RMA solder flux.
Wave soldering is the most strenuous of the processes.
To avoid the possibility of generating stresses due to
thermal shock, a preheat stage in the soldering process
is recommended, and the peak temperature of the solder
process should be rigidly controlled.
When using a reflow process, care should be taken to
ensure that the SM7 chip is not subjected to a thermal
gradient steeper than 4 degrees per second; the ideal
gradient being 2 degrees per second. During the soldering
process, preheating to within 100 degrees of the solder's
peak temperature is essential to minimize thermal shock.
Once the soldering process has been completed, it is
still necessary to ensure that any further thermal shocks
are avoided. One possible cause of thermal shock is hot
printed circuit boards being removed from the solder
process and subjected to cleaning solvents at room
temperature. The boards must be allowed to cool gradually
to less than 50ºC before cleaning.
Reflow Solder Profile
250
200
150
100
TEMPERATURE °C
50
0
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
PREHEAT DWELL
PREHEAT ZONE
Wave Solder Profile
300
250
200
150
100
TEMPERATURE °C
50
FIRST PREHEAT
MAXIMUM TEMPERATURE
230°C
SECONDS
ABOVE 183°C
RAMP RATE
<2°C/s
MAXIMUM WAVE 260°C
SECOND PREHEAT
40-80
Lead–free (Pb-free) Soldering Recommendations
The terminals of SM7 series devices are tin plated copper,
and the recommended Lead-free solder is 96.5/3.0/0.5
(SnAgCu) with an RMA flux, though there is a wide
selection of pastes and fluxes available that should be
compatible.
The reflow profile must be constrained by the maximums
in the Lead–free Reflow Profile. For Lead–free Wave
soldering, the Wave Solder Profile still applies.
Note: the Lead–free paste, flux and profile were used for
evaluation purposes by Littelfuse, based upon industry
standards and practices. There are multiple choices of all
three available, it is advised that the customer explores the
optimum combination for their process as processes vary
considerably from site to site.
SM7 Series Varistor
Lead–free Re-flow Solder Profile
78
Revised: May 8, 2013
0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
300
250
200
150
100
TEMPERATURE °C
MAXIMUM TEMPERATURE 250˚C,
TIME WITHIN 5˚C OF PEAK
20 SECONDS MAXIMUM
PREHEAT ZONE
50
0
0 1.0 2.0 3.0 4.0 5.0 6.0 7.0
Please refer to www.littelfuse.com/series/sm7.html for current information.
TIME (MINUTES)
RAMP RATE
<3˚C/s
TIME (MINUTES)
Specifications are subject to change without notice.
60 - 150 SEC
> 217˚C
© 2013 Littelfuse, Inc.
Varistor Products
Surface Mount Varistors > SM7 Series
Product Dimensions
11.5±0.3
0.3 max
1.5±0.3
6.5
3.5
13.1
Soldering Pad Layout
Tape & Reel Specifications
Carrier Tape
10°
P0
P2
A
A0
11.30
5°
2
6.2
D0
A
8.3±0.3
4.0±0.3
V115SM7-V175SM7
6.0±0.3 for
V230SM7-V510SM7
3.0±0.3
All dimensions shown
in milimeters
P1
B
B
D1
K0
F E
for
Part Numbering System
V 275 SM7
For “VARISTOR”
V
M(AC)
(Three digits -- 115V to 510V)
SM7 SERIES
SM7 Series
mm
W 16.00±0.30
T 0.40±0.05
A0 11.80±0.10
B0 8.60±0.10
W
5°
B0
3.60
T
B-B
K0 6.80±0.10
E 1.75±0.10
F 7.50±0.10
P0 4.00±0.10
P1 16.00±0.10
P2 2.00±0.10
D0 ø1.50 +0.10/-0
D1 ø1.50 +0.10/-0
A-A
Plastic Reel
Ø100
16.5
DETAIL H
© 2013 Littelfuse, Inc.
Specifications are subject to change without notice.
Please refer to www.littelfuse.com/series/sm7.html for current information.
21.5±0.4
Ø330
Ø13±0.2
DETAIL H
2±0.5
120°
Revised: May 8, 2013
Ø21±0.8
R1
79
NOTES:
1) All dimensions per EIA-481-c
2) 10 pitches cumulative tolerance on tape ±0.20mm
3) Quantity per 13 inch (330 mm) reel: 600 pcs
SM7 Series Varistor
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