SMT50-68 Littelfuse, Inc., SMT50-68 Datasheet

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SMT50-68

Manufacturer Part Number
SMT50-68
Description
Manufacturer
Littelfuse, Inc.
Datasheet
48
SMT50
The electrical characteristics of a SMT50 device are similar to
that of a self-gated Triac, but the SMT50 is a two terminal
device with no gate. The gate function is achieved by an
internal current controlled mechanism.
Like the T.V.S. diodes, the SMT50 has a standoff voltage (Vrm)
which should be equal to or greater than the operating
voltage of the system to be protected. At this voltage (Vrm)
the current consumption of the SMT50 is negligible and will
not affect the protected system.
When a transient occurs, the voltage across the SMT50 will
increase until the breakdown voltage (Vbr) is reached. At this
point the device will operate in a similar way to a T.V.S.
device and is in avalanche mode.
The voltage of the transient will now be limited and will only
increase by a few volts as the device diverts more current. As
this transient current rises, a level of current through the
1. When selecting a SMT50 device, it is important that
the Vrm of the device is equal to or greater than the
the operating voltage of the system.
2. The minimum Holding Current (Ih) must be greater
than the current the system is capable of delivering
otherwise the device will remain conducting following
a transient condition.
ELECTRICAL CHARACTERISTICS
SELECTING A SMT50
COMPLIES WITH THE
FOLLOWING STANDARDS
(CCITT) ITU-K20
(CCITT) ITU-K17
VDE0433
VDE0878
IEC-1000-4-5
FCC Part 68, lightning surge
type A
FCC Part 68, lightning surge
type B
Bellcore TR-NWT-001089
first level
Bellcore TR-NWT-001089
second level
CNET I31-24
PEAK SURGE
VOLTAGE
level 3
level 4
1000
1500
2000
2000
1500
1000
2500
1000
5000
1000
800
(V)
WAVEFORM
VOLTAGE
10/1000
1.2/500
0.5/700
10/700
10/700
10/700
10/700
10/160
10/560
1.2/50
9/720
2/10
2/10
(
w w w . l i t t e l f u s e . c o m
µS)
WAVEFORM
CURRENT
device is reached (Ibo) which causes the device to switch to a
fully conductive state such that the voltage across the device
is now only a few volts (Vt). The voltage at which the device
switched from the avalanche mode to the fully conductive
state (Vt) is known as the Breakover voltage (Vbo). When the
device is in the Vt state, high currents can be diverted
without damage to the SMT50 due to the low voltage across
the device, since the limiting factor in such devices is
dissipated power (V x I).
Resetting of the device to the non-conducting state is
controlled by the current flowing through the device. When
the current falls below a certain value, known as the Holding
Current (Ih), the device resets automatically.
As with the avalanche T.V.S. device, if the SMT50 is subjected
to a surge current which is beyond its maximum rating, then
the device will fail in short circuit mode, ensuring that the
equipment is ultimately protected.
10/1000
0.8/310
10/160
10/560
V-I Graph illustrating symbols
and terms for the SMT50 surge
protection device.
5/310
5/310
5/310
5/310
5/320
1/20
8/20
2/10
2/10
(
µS)
ADMISSIBLE IPP
100
150
150
(A)
25
38
50
50
50
75
55
25
50
25
NECESSARY
RESISTOR
12.5
11.5
11.5
(
6.5
10
-
-
-
-
-
-
-
-
)
I
I
I
I
pp
BO
H
RM
I
V
RM
V
R
V
BR
V
BO
V

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SMT50-68 Summary of contents

Page 1

... SMT50 ELECTRICAL CHARACTERISTICS The electrical characteristics of a SMT50 device are similar to that of a self-gated Triac, but the SMT50 is a two terminal device with no gate. The gate function is achieved by an internal current controlled mechanism. Like the T.V.S. diodes, the SMT50 has a standoff voltage (Vrm) which should be equal to or greater than the operating voltage of the system to be protected ...

Page 2

... Critical rate of rise of off-state voltage T Storage temperature range stg T Maximum junction temperature j T Maximum lead temperature for soldering during 10s L Type Marking Laser (µA) SMT50-62 A062 A068 SMT50-68 A100 SMT50-100 A120 SMT50-120 A130 SMT50-130 A180 SMT50-180 A200 SMT50-200 SMT50-220 A220 SMT50-240 A240 SMT50-270 A270 ° ...

Page 3

... SMT50 ...

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