SM8S24AHE3/2D Vishay, SM8S24AHE3/2D Datasheet - Page 2

• Manufacturer Part Number: SM8S24AHE3/2D
• Description: TVS 8W 24V 5% DO-218AB
• Manufacturer: Vishay

Specifications of SM8S24AHE3/2D

• Voltage - Reverse Standoff (typ): 24V
• Voltage - Breakdown: 26.7V
• Power (watts): 8W
• Polarization: Unidirectional
• Mounting Type: Surface Mount
• Package / Case: DO-218AB
• Polarity: Unidirectional
• Clamping Voltage: 38.9 V
• Operating Voltage: 24 V
• Breakdown Voltage: 26.7 V
• Peak Surge Current: 170 A
• Peak Pulse Power Dissipation: 6600 W
• Maximum Operating Temperature: + 175 C
• Minimum Operating Temperature: - 55 C
• Dimensions: 8.7(Max) mm W x 13.7(Max) mm L
• Reverse Stand-off Voltage Vrwm: 24V
• Breakdown Voltage Range: 26.7V To 29.5V
• Clamping Voltage Vc Max: 38.9V
• Diode Configuration: Unidirectional
• Peak Pulse Current Ippm: 170A
• Diode Case Style: DO-218AB
• No. Of Pins: 2
• Rohs Compliant: Yes
• Power Dissipation Pd: 8W
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Application Note
Vishay General Semiconductor
PRIMARY PROTECTION OF THE AUTOMOTIVE POWER LINE (LOAD DUMP)
Automotive electronics, such as electronic control units,
sensors, and entertainment systems, are connected to one
power line. The power sources for these electronics are the
battery and alternator, both of which have unstable output
voltages that are subject to temperature, operating status,
and other conditions. Additionally, ESD, spike noise, and
several kinds of transient and surge voltages are introduced
into the power and signal line from automotive systems that
use solenoid loads, such as fuel injection, valve, motor,
electrical, and hydrolytic controllers.
What is Load Dump?
The worst instances of surge voltage are generated when
the battery is disconnected when the engine is in operation,
and the alternator is supplying current to the power line of
the vehicle. This condition is known as “load dump”, and
most vehicle manufacturers and industry associations
specify a maximum voltage, line impedance, and time
duration for this load dump status, as shown in Figure 5.
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2
High Voltage induced
TABLE 1 - MAJOR LOAD DUMP TEST CONDITIONS FOR 14 V POWERTRAINS
JASO A-1
ISO 7637-2 pulse 5
A
by Alternator
Regulator
Battery
Fig. 4 - Typical Vehicle Power Bus
ESD or Lightning
V TOTAL (V
78.5 to 100.5
Transient Voltage Suppressors (TVS) for
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For technical questions within your region, please contact one of the following:
(V)
70
88
Automotive Electronic Protection
from Motor and Spark Plugs
P
)
TCU
Reaction Transient
Reverse
Voltage
65 to 87
ECU
Fig. 3 - Parameters of Voltage and Current
(V)
V
-
-
V
S
C
V
BR
Car-Audio
V
Air-Bag
WM
& ......
ABS
Forward
Reverse
Current
Current
12.0
12.0
13.5
(V)
V
A
I
Two well-known tests simulate this condition: the U.S.’s
ISO-7637-2 pulse 5 and Japan’s JASO A-1 for 14 V
powertrains and JASO D-1 for 27 V powertrains. In this
section we review the application of TVS for load dump in
14 V powertrains.
Specification and Results of Load Dump Tests
The U.S.’s ISO-7637-2 pulse 5 and Japan’s JASO A-1 tests
for 14 V powertrains are simulated in Table 1.
F
I
I
PP
R
Fig. 5 - Output Voltage of Alternator in Load Dump Condition
V
F
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0.5 to 4.0
Forward
Voltage
(Ω)
0.8
1.0
V
R
P
i
V
Output Voltage of Alternator
N
Connected
A
Battery
X
Disconnected
TIME
(ms)
200
200
400
Battery
Document Number: 88490
Load
Revision: 09-Aug-10
CYCLE TIME
1
1
1