Datasheet SR05.TC, SR05.TG Datasheet (Semtech Corporation)

PROTECTION PRODUCTS

SR05





RailClamp

Low Capacitance TVS Diode Array



Description

RailClamps are surge rated diode arrays designed to
protect high speed data interfaces. The SR series has
been specifically designed to protect sensitive compo­nents which are connected to data and transmission
lines from overvoltage caused by ESD (electrostatic
discharge), EFT (electrical fast transients), and light-

ning.

The unique design of the SR series devices incorpo­rates four surge rated, low capacitance steering diodes
and a TVS diode in a single package. During transient
conditions, the steering diodes direct the transient to
either the positive side of the power supply line or to
ground. The internal TVS diode prevents over-voltage
on the power line, protecting any downstream compo­nents.

The low capacitance array configuration allows the user
to protect two high-speed data or transmission lines.
The low inductance construction minimizes voltage
overshoot during high current surges.

Features

! ESD protection to IEC 61000-4-2, Level 4
! Array of surge rated diodes with internal TVS Diode
! Protects two I/O lines
! Low capacitance (<10pF) for high-speed interfaces
! Low clamping voltage
! Low operating voltage: 5.0V
! Solid-state silicon-avalanche technology

Mechanical Characteristics

! JEDEC SOT-143 package
! UL 497B listed
! Molding compound flammability rating: UL 94V-0
! Marking : R05
! Packaging : Tape and Reel per EIA 481

Applications

! USB Power & Data Line Protection
! Ethernet 10BaseT

2

! I

C Bus Protection

! Video Line Protection
! T1/E1 secondary IC Side Protection
! Portable Electronics
! Microcontroller Input Protection
! WAN/LAN Equipment
! ISDN S/T Interface

Circuit Diagram Schematic & PIN Configuration

Pin 4

1

Pin 2

Revision 9/2000

Pin 3

23

Pin 1

SOT-143 (Top View)

1

4

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PROTECTION PRODUCTS

Absolute Maximum Rating

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2 2000 Semtech Corp.

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PROTECTION PRODUCTS

e

Typical Characteristics

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

SR05

10

(kW)

PP

1

0.1

Peak Pulse Power - P

0.01

0.1 1 10 100 1000

Pulse Duration - tp (µµµµs)

Pulse Waveform

110
100

90
80
70

PP

60
50
40

Percent of I

30
20
10

0

0 5 10 15 20 25 30

-t

e

td = IPP/2

Time (µµµµs)

Waveform

Parameters:

tr = 8µs

td = 20µs

110
100

90

PP

80
70
60
50
40
30

% of Rated Power or I

20
10

0

0 25 50 75 100 125 150

Ambient Temperature - T

A

(oC)

Clamping Voltage vs. Peak Pulse Current

10

9
8

(V)

F

7
6
5
4
3

Forward Voltage - V

2
1
0

0 5 10 15 20 25 30 35 40 45 50

Forward Current - I

(A)

F

Waveform

Parameters:

td = 20µs

tr = 8µs

Forward Voltage vs. Forward Current Capacitance vs. Reverse Voltage

10

9
8

(V)

F

7
6
5
4
3

Forward Voltage - V

2
1
0

0 5 10 15 20 25 30 35 40 45 50

Forward Current - I

(A)

F

Waveform

Parameters:

tr = 8µs

td = 20µs

3 2000 Semtech Corp.

0

-2

-4

-6

-8

-10

-12

% Change in Capacitanc

-14

-16
0123456

Reverse Voltage (V)

I/O to GND

f = 1MHz

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PROTECTION PRODUCTS

Applications Information

Device Connection Options for Protection of Two
High-Speed Data Lines

The SR05 TVS is designed to protect two 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
steering diodes are forward biased, conducting the
transient current away from the sensitive circuitry.
Data lines are connected at pins 2 and 3. The nega­tive reference (REF1) is connected at pin 1. This pin
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 (REF2) is connected at pin 4.
The options for connecting the positive reference are
as follows:

1. To protect data lines and the power line, connect
pin 4 directly to the positive supply rail (VCC). In this
configuration the data lines are referenced to the
supply voltage. The internal TVS diode prevents
over-voltage on the supply rail.

2. The SR05 can be isolated from the power supply by
adding a series resistor between pin 4 and VCC. A
value of 10kΩ is recommended. The internal TVS
and 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,
the internal TVS may be used as the reference. In
this case, pin 4 is not connected. 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).

) the

F

SR05

Data Line and Power Supply Protection Using Vcc as
reference

Data Line Protection with Bias and Power Supply
Isolation Resistor

Data Line Protection Using Internal TVS Diode as
Reference

ESD Protection With RailClamps

RailClamps are optimized for ESD protection using the
rail-to-rail topology. Along with good board layout,
these devices virtually eliminate the disadvantages of
using discrete components to implement this topology.
Consider the situation shown in Figure 1 where dis­crete diodes or diode arrays are configured for rail-to­rail protection on a high speed line. During positive
duration ESD events, the top diode will be forward
biased when the voltage on the protected line exceeds
the reference voltage plus the V

drop of the diode.

F

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PROTECTION PRODUCTS

Applications Information (continued)

For negative events, the bottom diode will be biased
when the voltage exceeds the V
approximation, the clamping voltage due to the charac­teristics of the protection diodes is given by:

V

= VCC + VF(for positive duration pulses)

PIN Descriptions

C

V

C

= -V

F

(for negative duration pulses)

However, for fast rise time transient events, the
effects of parasitic inductance must also be consid­ered as shown in Figure 2. Therefore, the actual
clamping voltage seen by the protected circuit will be:

of the diode. At first

F

SR05

V

= VCC + VF + LP di

C

VC = -VF - LG di

ESD

/dt (for positive duration pulses)

ESD

/dt (for negative duration pulses)

ESD current reaches a peak amplitude of 30A in 1ns
for a level 4 ESD contact discharge per IEC 1000-4-2.
Therefore, the voltage overshoot due to 1nH of series
inductance is:

V = LP di

/dt = 1X10-9 (30 / 1X10-9) = 30V

ESD

Example:
Consider a VCC = 5V, a typical VF of 30V (at 30A) for the
steering diode and a series trace inductance of 10nH.
The clamping voltage seen by the protected IC for a
positive 8kV (30A) ESD pulse will be:

VC = 5V + 30V + (10nH X 30V/nH) = 335V
This does not take into account that the ESD current is

directed into the supply rail, potentially damaging any
components that are attached to that rail. Also note
that it is not uncommon for the VF of discrete diodes to
exceed the damage threshold of the protected IC. This
is due to the relatively small junction area of typical
discrete components. It is also possible that the
power dissipation capability of the discrete diode will
be exceeded, thus destroying the device.

Figure 1 - “Rail-Figure 1 - “Rail-

Figure 1 - “Rail-

Figure 1 - “Rail-Figure 1 - “Rail-

Figure 2 - The Effects of Parasitic InductanceFigure 2 - The Effects of Parasitic Inductance

Figure 2 - The Effects of Parasitic Inductance

Figure 2 - The Effects of Parasitic InductanceFigure 2 - The Effects of Parasitic Inductance

When Using Discrete Components to ImplementWhen Using Discrete Components to Implement

When Using Discrete Components to Implement

When Using Discrete Components to ImplementWhen Using Discrete Components to Implement

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The RailClamp is designed to overcome the inherent
disadvantages of using discrete signal diodes for ESD
suppression. The RailClamp’s integrated TVS diode
helps to mitigate the effects of parasitic inductance in

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5 2000 Semtech Corp.

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PROTECTION PRODUCTS

Applications Information (continued)

the power supply connection. During an ESD event,
the current will be directed through the integrated TVS
diode to ground. The total clamping voltage seen by
the protected IC due to this path will be:

SR05

VC = V

F(RailClamp)

+ V

TVS

This is given in the data sheet as the rated clamping
voltage of the device. For a SR05 the typical clamping
voltage is <16V at I

=30A. The diodes internal to the

PP

RailClamp are low capacitance, fast switching devices
that are rated to handle transient currents and main­tain excellent forward voltage characteristics.

Universal Serial Bus ESD Protection

The figure below illustrates how to use the SR05 to
protect one upstream USB port and the SRDA05-4 to
protect two downstream USB ports. When the voltage
on the data lines exceed the bus voltage (plus one
diode drop), the internal rectifiers are forward biased
conducting the transient current away from the pro­tected controller chip. The TVS diode directs the surge
to ground. The TVS diode also acts to suppress ESD
strikes directly on the voltage bus. Thus, both power
and data pins are protected with a single device.
Reference Semtech application note SI96-18 for
further information.

6 2000 Semtech Corp.

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PROTECTION PRODUCTS

Typical Applications

SR05

Universal Serial Bus ESD Protection

ISDN S/T Interface Protection

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PROTECTION PRODUCTS

Outline Drawing - SOT-143

SR05

Notes:
(1) Controlling dimension: Inch (unless otherwise specified).
(2) Dimension A and B do not include mold protrusions. Mold protrusions are .006” max.

Land Pattern - SOT-143

8 2000 Semtech Corp.

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PROTECTION PRODUCTS

Marking Codes

SR05

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Ordering Information

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Contact Information

Semtech Corporation

Protection Products Division

652 Mitchell Rd., Newbury Park, CA 91320

Phone: [phone] FAX [phone]

9 2000 Semtech Corp.

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