Littelfuse SM20 Series Catalog Page
SM20 Varistor Series
Agency Approvals
Varistor Products
Surface Mount Varistors > SM20 Series
Description
The Littelfuse 20mm SMD Series is a surface-mount
metal oxide varistor device, for use in applications
requiring hi-energy / transient current capability.
The AC rated parts are designed to operate
continuously across AC power lines. The DC rated
parts are suitable for Automotive applications. The
series comprises a Nylon molded package with folded
tin plated metal leads for soldering to board.
The SMD Series is based on radial 20mm internal
varistor element with similar characteristics to
the Littelfuse LA / ZA series of varistors.
Agency Agency File Number
E320116
Features
• DC Voltage
Rating 26VDC
• AC Voltage Rating
175 - 320AC
• No De-Rating up
to 85°C ambient
• Low voltage
devices specified
for automotive load
dump energy
• Available in "waffle"
tray packaging
• Lead-Free, HalogenFree and RoHS
Compliant
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
) 20 to 320 V
M(AC)RMS
)26V
M(DC)
Transients:
Peak Pulse Current (ITM) 8/20μs Current Wave, Single Pulse up to 6500 A
Single Pulse Energy Capability (W
Load Dump Energy Capability (td>=30ms) 160 J
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
) -55 to +125
STG
V
) of Clamping Voltage (VC) at Specified Test Current <0.01 %/OC
) 10/1000μs Current Wave 165 J
TM
) -40 to +85
A
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.
SM20 Series Units
O
C
O
C
2500 V
SM20 Series
©2010 Littelfuse, Inc.
Specifications are subject to change without notice.
Please refer to www.littelfuse.com/series/sm20.html for current information.
Revision: May 11, 2010
SM20 Series Varistor
Varistor Products
Surface Mount Varistors > SM20 Series
SM20 Series Ratings & Specifications
Maximum Rating (85°C) Specifications (25°C)
Continuous Transient
Part
Number
Branding
V
RMS
V
M(AC)
(V) (V) (J) (A) (V) (V) (V) (A) (pF)
V
V
M(DC)
V26SM20 26SM20 20 26
DC
Energy
10 x 1000μs
WTM
1x pulse
20
160 (note 1)
Peak Current
8 x 20μs
ITM
1x pulse
2000
Varistor Voltage
at 1mA DC
Test Current
V
Min V
NOM
NOM
32
(10mA)40(10mA)
Max V
V175SM20 175SM20 175 225 90 6500 247 303 455 100 1400
V230SM20 230SM20 230 300 122 6500 324 396 595 100 1100
V250SM20 250SM20 250 330 130 6500 354 429 650 100 1000
V275SM20 275SM20 275 369 140 6500 389 473 710 100 900
V300SM20 300SM20 300 405 165 6500 420 517 775 100 800
V320SM20 320SM20 320 420 150 6500 462 540 810 100 750
1. Energy rating for impulse duration of 30ms minimum to one half of peak current (automotive load dump).
Maximum
Clamping
Voltage
8 x 20 μs
C
Capacitance
f = 1MHz
IPK C
63 20 12000
Typical
Peak Current, Energy and Power Derating Curve
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 (
o
C)
Peak Pulse Current Test Waveform for Clamping Voltage
100
Repetitive Surge Capability
V175SM20 - V320SM20
10,000
1
5,000
2,000
1,000
500
200
100
50
20
INDEFINITE
SURGE CURRENT (A)
10
5
2
1
20 100 1,000 10,000
2
10
IMPULSE DURATION (μs)
MODEL SIZE 20mm
V175SM20 - V320SM20
2
10
3
10
4
10
5
10
6
10
50
PERCENT OF PEAK VALUE Test
0
O
1
t
t
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:
8μs = T1 = Rise Time
20μs = T2 = Decay Time
SM20 Series Varistor
TIM E
Revision: May 11, 2010
©2010 Littelfuse, Inc.
Please refer to www.littelfuse.com/series/sm20.html for current information.
Specifications are subject to change without notice.
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