PROTECTION PRODUCTS
1
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PROTECTION PRODUCTS
SRDA70-4
RailClamp
Low Capacitance TVS Diode Array
u
Transient protection for high speed data lines to
IEC 61000-4-2 (ESD) 15kV (air), 8kV (contact)
IEC 61000-4-4 (EFT) 40A (5/50ns)
IEC 61000-4-5 (Lightning) 1kV, 24A (8/20s)
u
Array of surge rated diodes
u
Protects four I/O lines
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Low capacitance for high-speed interfaces
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High surge capability
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Low forward voltage characteristics
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Solid-state silicon avalanche technology
Description
Features
Circuit Diagram
Schematic & PIN Configuration
Revision 9/2000
Applications
Mechanical Characteristics
REF 1
I/O 1
I/O 2
I/O 3
I/O 4
REF 2
I/O 1
I/O 2
REF 1
REF 1
REF 2
REF 2
I/O 3
I/O 4
SO-8 (Top View)
RailClamps are surge rated diode arrays designed to
protect high speed data interfaces. The SRDA70-4 has
been specifically designed to protect sensitive compo-
nents which are connected to data and transmission
lines from over-voltages caused by ESD (electrostatic
discharge), EFT (electrical fast transients), and light-
ning.
The unique design of the SRDA70-4 integrates eight
surge rated, low capacitance steering diodes in a low
profile SO-8 package. During transient conditions, the
steering diodes direct the transient to either the
positive side of the power supply line or to ground. The
SRDA70-4 may be used as a stand alone device or in
conjunction with TVS diodes for enhanced protection.
The low capacitance array configuration allows the user
to protect four high speed data or I/O lines. The low
inductance construction minimizes voltage overshoot
during high current surges.
u
JEDEC SO-8 package
u
UL 497B listed
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Molding compound flammability rating: UL 94V-0
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Marking : Part number, date code, logo
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Packaging : Tube or Tape and Reel per EIA 481
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Latch-Up Protection
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Microcontroller Input Protection
u
Token Ring
u
I
2
C Bus Protection
u
Video Line Protection
u
Set Top Box I/O
u
LAN/WAN Equipment
2
2000 Semtech Corp.
www.semtech.com
PROTECTION PRODUCTS
PROTECTION PRODUCTS
SRDA70-4
Absolute Maximum Rating
Electrical Characteristics
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3
2000 Semtech Corp.
www.semtech.com
PROTECTION PRODUCTS
SRDA70-4
Typical Characteristics
Non-Repetitive Peak Pulse Power vs. Pulse Time
Power Derating Curve
0.01
0.1
1
10
0.1
1
10
100
1000
Pulse Duration - tp (
s)
Peak Pulse Power - P
PP
(kW)
0
10
20
30
40
50
60
70
80
90
100
110
0
25
50
75
100
125
150
Ambient Temperature - T
A
(
o
C)
% of Rated Power or I
PP
Variation of Capacitance vs. Reverse Voltage
0
10
20
30
40
50
60
70
80
90
100
110
0
5
10
15
20
25
30
Time (
s)
Percent of I
PP
e
-t
td = I
PP
/2
Waveform
Parameters:
tr = 8
s
td = 20
s
Pulse Waveform
-16
-14
-12
-10
-8
-6
-4
-2
0
0
1
2
3
4
5
6
Reverse Voltage (V)
% Change in Capacitance
I/O to GND
f = 1MHz
Foward Voltage vs. Forward Current
0
1
2
3
4
5
6
7
8
9
10
0
5
10
15
20
25
30
35
40
45
50
Forward Current - I
F
(A)
Forward Voltage - V
F
(V)
Waveform
Parameters:
tr = 8
s
td = 20
s
4
2000 Semtech Corp.
www.semtech.com
PROTECTION PRODUCTS
PROTECTION PRODUCTS
SRDA70-4
Device Connection Options for Protection of Four
High-Speed Data Lines
The SRDA70-4 TVS is designed to protect four data
lines from transient over-voltages by clamping them to
a fixed reference. When the voltage on the protected
line exceeds the reference voltage (plus diode V
F
) the
steering diodes are forward biased, conducting the
transient current away from the sensitive circuitry.
Data lines are connected at pins 1, 4, 6 and 7. The
negative reference (REF2) is connected at pins 5 & 8.
These pins should be connected directly to a ground
plane on the board for best results. The path length is
kept as short as possible to minimize parasitic induc-
tance.
The positive reference (REF1) is connected at pins 2 &
3. The options for connecting the positive reference
are as follows:
1. To protect data lines and the power line, connect
pins 2 & 3 directly to the positive supply rail (V
CC
).
In this configuration the data lines are referenced
to the supply voltage. An external TVS diode may
be added between the supply rail and ground in
order to prevent over-voltage on the supply rail.
2. The SRDA70-4 can be isolated from the power
supply by adding a series resistor between pins 2 &
3 and V
CC
. A value of 10kW is recommended. The
internal steering diodes remain biased, providing
the advantage of lower capacitance.
3. In applications where no positive supply reference
is available, or complete supply isolation is desired,
an external TVS diode may be used as the refer-
ence. The steering diodes will begin to conduct
when the voltage on the protected line exceeds the
working voltage of the TVS (plus one diode drop).
I/O Protection
Microcontroller Protection
SRDA70-4
Applications Information
5
2000 Semtech Corp.
www.semtech.com
PROTECTION PRODUCTS
SRDA70-4
Land Pattern - SO-8
Outline Drawing - SO-8
6
2000 Semtech Corp.
www.semtech.com
PROTECTION PRODUCTS
PROTECTION PRODUCTS
SRDA70-4
Contact Information
Semtech Corporation
Protection Products Division
652 Mitchell Rd., Newbury Park, CA 91320
Phone: (805)498-2111 FAX (805)498-3804
Ordering Information
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