Littelfuse SM20 Varistor Series - Manual (Page 2)

© 2014 Littelfuse, Inc. 82
Revised: February 6, 2014
Varistor Products
SM20 Series Varistor
Surface Mount Varistors > SM20 Series
Specifications are subject to change without notice.
Please refer to www.littelfuse.com/series/sm20.html for current information.
Repetitive Surge Capability
V175SM20 - V320SM20
10,000
2,000
200
100
50
20
10
5
2
500
20 100 1,000 10,000
IMPULSE DURATION ( µs)
SURGE CURRENT (A)
1
2
10 4
10 5
10 6
MODEL SIZE 20mm
V175SM20 - V320SM20
10 3
INDEFINITE
1,000
10 2
10
5,000
1
For applications exceeding 85ºC ambient temperature, the peak
surge current and energy ratings must be reduced as shown below
Peak Pulse Current Test Waveform for Clamping Voltage
Peak Current, Energy and Power Derating Curve
0
1
= Virtual Origin of Wave
T = Time from 10% to 90% of Peak
T
1
= Rise Time = 1.25 x T
T
2
= Decay Time
Example - For an 8/20 µs Current Waveform:
8µs = T
1
= Rise Time
20µs = T
2
= Decay Time
PERCEN
T OF PEAK
V
ALUE
Test
0
50
100
TIM E
t
1
t
2
t
O
1
100
90
80
70
60
50
40
30
20
10
0
-55 50 60 70 80 90 100 110 120 130 140 150
AMBIENT TEMPERATURE ( o C)
PERCENT OF
RA
TED V
ALUE
FIGURE 1. CURRENT, ENERGY AND POWER DERATING
CURVE
SM20 Series Ratings & Specifications
Maximum Rating (85°C) Specifications (25°C)
Continuous Transient
Varistor Voltage
at 1mA DC
Test Current
Maximum
Clamping
Voltage
8 x 20 µs
Typical
Capacitance
f = 1MHz
V
RMS
V
DC
Energy
10 x 1000 µs
Peak Current
8 x 20 µs
Part
Number
Branding
V
M(AC)
V
M(DC)
W
TM
1x pulse
I
TM
1x pulse
V
NOM
Min V
NOM
Max V
C
I
PK
C
(V) (V) (J) (A) (V) (V) (V) (A) (pF)
V26SM20 26SM20 20 26
20
160 (note 1)
2000
32
(10mA)
40
(10mA)
63 20 12000
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).