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PROTECTION PRODUCTS Description
RailClamps are surge rated diode arrays designed to protect high speed data interfaces. The SRDA70-4 has been specifically designed to protect sensitive components which are connected to data and transmission lines from over-voltages caused by ESD (electrostatic discharge), EFT (electrical fast transients), and lightning. 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.
RailClampO Low Capacitance TVS Diode Array
Features
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) Array of surge rated diodes Protects four I/O lines Low capacitance for high-speed interfaces High surge capability Low forward voltage characteristics Solid-state silicon avalanche technology
SRDA70-4
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Mechanical Characteristics
JEDEC SO-8 package UL 497B listed Molding compound flammability rating: UL 94V-0 Marking : Part number, date code, logo Packaging : Tube or Tape and Reel per EIA 481
Applications
Latch-Up Protection Microcontroller Input Protection Token Ring I2C Bus Protection Video Line Protection Set Top Box I/O LAN/WAN Equipment
Circuit Diagram
Schematic & PIN Configuration
REF 1
I/O 1 REF 1
I/O 1 I/O 2 I/O 3 I/O 4
REF 2 I/O 4 I/O 3 REF 2
REF 1 I/O 2
REF 2
SO-8 (Top View)
Revision 9/2000 1 www.semtech.com
SRDA70-4
PROTECTION PRODUCTS Absolute Maximum Rating
R ating Peak Pulse Current (tp = 8/20 s) Rectifier Rep etitive Peak Reverse Voltage Th ermal Resistance, Junction to A mb ient Th ermal Resistance, Junction to Case Lead Sold ering Temp erature Op erating Temp erature Storage Temp erature Symbo l I PP V RRM qJA qJC TL TJ TSTG Value 24 70 163 38.8 260 (10 sec.) -55 to +125 -55 to +150 Units A V C /W C /W C C C
Electrical Characteristics
SR DA70-4 Par ame te r Rectifier Rep etitive Peak reverse Voltage Reverse Breakd ow n Voltage Reverse Leakage Current Forw ard Voltage Forw ard Voltage Junction Cap acitance Symbo l V RRM V BR IR VF VF Cj It = 50 A V RWM = 70V, T=25C IPP = 1A , tp = 8/20 s IPP = 10A , tp = 8/20 s Betw een I/O p ins and Gnd V R = 0V, f = 1MHz Betw een I/O p ins V R = 0V, f = 1MHz 4 85 5 1.3 3.3 15 Co nd itio ns Minimum Typ ical Maximum 70 Units V V A V V pF
pF
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SRDA70-4
PROTECTION PRODUCTS Typical Characteristics
Non-Repetitive Peak Pulse Power vs. Pulse Time
10
110 100
Power Derating Curve
Peak Pulse Power - P PP (kW)
% of Rated Power or IPP
90 80 70 60 50 40 30 20 10
1
0.1
0.01 0.1 1 10 Pulse Duration - tp (s) 100 1000
0 0 25 50 75 100 125 150 Ambient Temperature - TA (oC)
Pulse Waveform
110 100 90 80 Percent of IPP 70 60 50 40 30 20 10 0 0 5 10 15 Time (s) 20 25 30 td = IPP/2 e
-t
Variation of Capacitance vs. Reverse Voltage
0 Waveform Parameters: tr = 8s td = 20s -2 % Change in Capacitance -4 -6 -8 -10 -12 -14 -16 0 1 2 3 Reverse Voltage (V) 4 5 6 I/O to GND f = 1MHz
Foward Voltage vs. Forward Current
10 9 Forward Voltage - V F (V) 8 7 6 5 4 3 2 1 0 0 5 10 15 20 25 30 35 40 45 50 Forward Current - IF (A) Waveform Parameters: tr = 8s td = 20s
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SRDA70-4
PROTECTION PRODUCTS Applications Information
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 VF) 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 inductance. 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 (VCC). 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 VCC. 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 reference. 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
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SRDA70-4
PROTECTION PRODUCTS Outline Drawing - SO-8
Land Pattern - SO-8
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SRDA70-4
PROTECTION PRODUCTS Ordering Information
Par t Numbe r SRDA 70-4.TB SRDA 70-4.TE Qty p e r Reel 500 2500 R e e l Size 7 Inch 13 Inch
Contact Information
Semtech Corporation Protection Products Division 652 Mitchell Rd., Newbury Park, CA 91320 Phone: (805)498-2111 FAX (805)498-3804
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