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PROTECTION PRODUCTS

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PROTECTION PRODUCTS - RailClamp®®

®®

SRDA3.3-4

RailClamp®®

®®

Low Capacitance TVS Array

Description Features

Circuit Diagram Schematic and PIN Configuration

Revision 01/15/08

RailClamps are surge rated diode arrays designed to

protect high speed data interfaces. The SRDA series

has been specifically designed to protect sensitive

components which are connected to data and trans-

mission lines from overvoltage caused by electrostatic

discharge (ESD), electrical fast transients (EFT), and

lightning.

The unique design incorporates surge rated, low

capacitance steering diodes and a TVS diode in a

single package. During transient conditions, the

steering diodes direct the transient current to ground

via the internal low voltage TVS. The TVS diode clamps

the transient voltage to a safe level. The low capaci-

tance array configuration allows the user to protect up

to four high-speed data lines.

The SRDA3.3-4 is constructed using Semtech’s

proprietary EPD process technology. The EPD process

provides low stand-off voltages with significant reduc-

tions in leakage current and capacitance over silicon-

avalanche diode processes. They feature a true

operating voltage of 3.3 volts for superior protection.

These devices are in a 8-pin SOIC package. It mea-

sures 3.9 x 4.9mm. They are available with a SnPb or

RoHS/WEEE compliant matte tin lead finish. The high

surge capability (Ipp=25A, tp=8/20μs) means it can be

used in high threat environments in applications such

as CO/CPE equipment, telecommunication lines, and

video lines.

Applications

Mechanical Characteristics

T1/E1 secondary IC Side Protection

T3/E3 secondary IC Side Protection

Analog Video Protection

Microcontroller Input Protection

Base stations

I2C Bus Protection

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) 24A (8/20μs)

Array of surge rated diodes with internal TVS diode

Protects four I/O lines

Low capacitance (<15pF) for high-speed interfaces

Low operating voltage: 3.3V

Low clamping voltage

Solid-state technology

JEDEC SOIC-8 package

Lead Finish: SnPb or Matte Sn

Molding compound flammability rating: UL 94V-0

Marking : Part number, date code, logo

Packaging : Tape and Reel per EIA 481

S0-8 (Top View)

I/O 3

I/O 4

GND

I/O 1

I/O 2

2, 3

I/O 1 I/O 2 I/O 3 I/O 4

5, 8

PROTECTION PRODUCTS

SRDA3.3-4

Absolute Maximum Rating

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Electrical Characteristics (T=25oC)

PROTECTION PRODUCTS

SRDA3.3-4

Typical Characteristics

Non-Repetitive Peak Pulse Power vs. Pulse Time Power Derating Curve

0.01

0.1

0.1 1 10 100 1000

Pulse Duratio n - tp (µs)

Peak Pulse Pow er - Ppk (kW)

100

110

0 25 50 75 100 125 150

Ambient Temperatur e - TA (oC)

% of Rated Power or I

Clamping Voltage vs. Peak Pulse Current

100

110

0 5 10 15 20 25 30

Time (µs)

Percent o f I PP

e-t

td = IPP/2

Waveform

Par a me t e r s:

tr = 8µs

td = 20µs

Pulse Waveform

Normalized Junction Capacitance

vs. Reverse Voltage

0 5 10 15 20 25

Peak Pulse Current - Ipp (A)

Clamping Voltage - Vc (V)

Waveform

Parameters:

tr = 8∠

td = 20∠

0.88

0.9

0.92

0.94

0.96

0.98

1.02

1.04

00.511.522.533.5

Reverse Voltage - VR (V)

Cj ( V R) / Cj (VR = 0 )

PROTECTION PRODUCTS

SRDA3.3-4

Data Line Protection Using Internal TVS Diode as

Reference

Applications Information

Device Connection Options for Protection of Four

High-Speed Data Lines

These devices are designed to protect low voltage data

lines operating at 3.3 volts. When the voltage on the

protected line exceeds the punch-through or “turn-on”

voltage of the TVS diode, 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. Pins 5

and 8 should be connected directly to a ground plane.

The path length is kept as short as possible to

minimize parasitic inductance.

Note that pins 2 and 3 are connected internally to the

cathode of the low voltage TVS. It is not recommended

that these pins be directly connected to a DC source

greater than the snap-back votlage (VSB) as the device

can latch on as described below.

EPD TVS Characteristics

These devices are constructed using Semtech’s

proprietary EPD technology. By utilizing the EPD tech-

nology, the SRDA3.3-4 can effectively operate at 3.3V

while maintaining excellent electrical characteristics.

The EPD TVS employs a complex nppn structure in

contrast to the pn structure normally found in tradi-

tional silicon-avalanche TVS diodes. Since the EPD

TVS devices use a 4-layer structure, they exhibit a

slightly different IV characteristic curve when compared

to conventional devices. During normal operation, the

device represents a high-impedance to the circuit up to

the device working voltage (VRWM). During an ESD

event, the device will begin to conduct and will enter a

low impedance state when the punch through voltage

(VPT) is exceeded. Unlike a conventional device, the low

voltage TVS will exhibit a slight negative resistance

characteristic as it conducts current. This characteris-

tic aids in lowering the clamping voltage of the device,

but must be considered in applications where DC

voltages are present.

When the TVS is conducting current, it will exhibit a

slight “snap-back” or negative resistance characteris-

tics due to its structure. This point is defined on the

curve by the snap-back voltage (VSB) and snap-back

EPD TVS IV Characteristic Curve

IPP

ISB

IPT

RWM VV PT VC

VBRR

IBRR

current (ISB). To return to a non-conducting state, the

current through the device must fall below the ISB

(approximately <50mA) and the voltage must fall below

the VSB (normally 2.8 volts for a 3.3V device). If a 3.3V

TVS is connected to 3.3V DC source, it will never fall

below the snap-back voltage of 2.8V and will therefore

stay in a conducting state.

PROTECTION PRODUCTS

SRDA3.3-4

T1/E1 Interface Protection (GR-1089 Long Haul)

Typical Applications

SRDA3.3-4

LC01-6

PROTECTION PRODUCTS

SRDA3.3-4

Applications Information - Spice Model

SRDA3.3-4 Spice Model

sretemaraPecipS4-3.3ADRS

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SIpmA11-E290.221-E651.241-E90.6

VBtloV08604245.3

JVtloV26

.046.08.31

SRmhO081.0551.0022.0

VBIpmA3-E13-E13-E01

OJCdaraF21-E2.521-E2.621-E54

TTces9-E145.29-E145.29-E145.2

M--850.0850.0111.

N--1.11.11.1

GEVe11.111.111.1

Pin 1, 4, 6, or 7

Pin 2 & 3

Pin 5 & 8

0.6 nH

PROTECTION PRODUCTS

SRDA3.3-4

Land Pattern - SO-8

Outline Drawing - SO-8

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2X N/2 TIPS

SEATING

aaa C

E/2

bbb C A-B D

ccc C e/2

A2 SEE DETAIL A

SIDE VIEW

DETAIL A

(L1) 01

0.25

GAGE

PLANE

3. DIMENSIONS "E1" AND "D" DO NOT INCLUDE MOLD FLASH, PROTRUSIONS

OR GATE BURRS.

-B-

CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).

DATUMS AND TO BE DETERMINED AT DATUM PLANE

NOTES:

2. -A- -H-

REFERENCE JEDEC STD MS-012, VARIATION AA.

.050 BSC

.236 BSC

.010

.150

.189 .154

.193

.012 -

0.25

1.27 BSC

6.00 BSC

3.90

4.90

.157

.197 3.80

4.80

.020 0.31

4.00

5.00

0.51

(.041)

.004

.008

.028

0°

.016

.007

.049

.004

.053

8° 0°

0.20

0.10

-8°

0.40

0.17

1.25

0.10

.041

.010

.069

.065

.010 1.35

(1.04)

0.72

1.04

0.25

-1.75

1.65

0.25

.010 .020 0.50

bbb

aaa

ccc

DIM MIN

MILLIMETERS

NOM

DIMENSIONS

INCHES

MIN MAX MAXNOM

(.205) (5.20)

.118 1.27

.050 0.60.024 2.20.087 7.40.291

INCHES

DIMENSIONS

DIM

MILLIMETERS

THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY.

CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR

COMPANY'S MANUFACTURING GUIDELINES ARE MET.

NOTES:

REFERENCE IPC-SM-782A, RLP NO. 300A.

PROTECTION PRODUCTS

SRDA3.3-4

Ordering Information

Note: Lead-free devices are RoHS/WEEE Compliant

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SC YYWW

SRDA3.3-4

PHIL

Marking Diagram

Note:

YYWW = Date Code

Tape and Reel Specification

Device Orientation in Tape

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mm21mm2.8 mm1.0+5.1

mm0.0-

mm5.101.±057.1

50.0±5.5

mm mm5.4 1.0±0.4

1.0±0.4

50.0±0.2

mm mm4.0

mm0.21

3.0±

0A0B0K

mm02.0-/+05.6mm02.0-/+04.5mm01.0-/+00.2

Pin 1 Location

User Direction of feed

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Contact Information for Semtech International AG