CompVdDG

2010
Protection Design Guide for
Computer, Set Top Box, HDTV/Monitor Interfaces
www.semtech.com
Table of Contents
Computer & Digital Video Protection
Section I: Introduction & Background
Trends in circuit protection > 4
Semtech advantages process & technology > 5
Threat environment > 6
TVS diode basics > 8
Clamping voltage > 9
Layout guidelines > 10
Section II: Protection Solutions
Parts & features > 11
High speed interfaces protection (RClamp® 0544T) > 14
USB protection (RClamp® 0522T) > 15
USB with integration VBus protection (RClamp® 0854P) > 16
SD/MicroSD protection ( EClamp® 2410P)> > 17
Gigabit ethernet protection (RClamp® 2504N) > 18
10/100 ethernet protection (RClamp® 2504P) > 19
xDSL circuit protection (SR12) > 20
Audio port protection (EClamp® 2422N) > 21
Antenna protection (RClamp® 0531T) > 22
Section III: Protection Applications
IEC61000-4-x transient immunity standards > 24
DisplayPort protection > 28
HDMI protection > 29
LVDS protection > 30
USB protection > 31
Gigabit ethernet protection >32
Safeguarding ethernet interfaces from Cable Discharge >35
TVS package drawings >37
Introduction & Background
Computer & Digital Video Protection
The Need for Robust Circuit Protection
Le
v
M
HB
2k
V
Cost of ESD design dependent on:
• Chip area
• Respins
• Resources
• Circuit performance
• Time-to-market
el
Today’s digital communication integrated circuits (ICs) and transceivers are
faster, more efficient, consume less power, and are smaller than ever before.
Yet the advances in IC technology and enhanced chip performance has come
with a notable trade off: increased susceptibility to damage from ESD, cable
discharge and lightning. Not only are transistor geometry sizes scaling down
at a remarkable pace, leading to more sensitive circuits, but the on-chip
protection is increasingly being sacrificed in favor of accommodating greater
performance in the chip. As this trend progresses, high performance system
level transient voltage protection will be needed more than ever before.
V
1k
HB
M
Le
ve
l
ling Level
Safe Hand
ESD Association’s Recommended
Safe-Handling Level for On-Chip Protection
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
4
Introduction & Background
Computer & Digital Video Protection
Semtech Advantages
Process & Technology
The Semtech protection portfolio offers key advantages over industry standard TVS
protection devices. These performance advantages are achieved with Semtech’s
advanced processing technology. This process technology enables the production
of TVS diode arrays with sub 5 volt working voltage, low clamping voltage, and
sub-picofarad capacitance. The compact design of the Semtech process allows
devices to be housed in low-profile, space-saving packages. Lower working voltage
means that the protection device can respond more quickly, shunt transient voltage
spikes at a lower threshold, and thus provide a lower clamping voltage. As the
transient voltage sensitivity of transceivers increases, designing low working voltage
protection devices is a critical component for protecting today’s systems.
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
5
Introduction & Background
Computer & Digital Video Protection
Threat Environment
Computer and high end consumer electronics interfaces are vulnerable to a variety of different transient voltage threats. These threats
include Electrostatic Discharge (ESD), Cable Discharge Events (CDE) and lightning surge. Interfaces that are accessible to human contact,
such as RJ-45 ports, are vulnerable to transient voltage threats from ESD and cable discharge transients. Additionally, Ethernet Physical
Layer Chips (PHYs) within the networking infrastructure are highly vulnerable to lightning threats. When choosing and designing an
appropriate protection scheme, you should consider these transients and their inherent electrical characteristics.
Electrostatic Discharge (ESD)
IEC 61000-4-2 divides the ESD into four threat levels. Test voltages
at the threat levels range from 2kV to 15kV with peak discharge
currents as high as 30A. Most manufacturers adhere to the most
stringent level, level 4, which defines a +/-15kV air discharge test
and a +/-8kV contact discharge test. However, many manufacturers
test their equipment beyond these levels. The ESD waveform as
defined by IEC 61000-4-2 reaches peak magnitude in 700ps to 1ns
and has a total duration of only 60ns. While the ESD pulse contains
little energy, the resulting effect can be devastating to sensitive
semiconductor devices. Sensitive points of the equipment are to be
tested with a combination of positive and negative discharges.
Several models exist to simulate ESD events. Each is designed
to describe the threat in a real world environment. The discharge
model is typically a voltage source feeding a resistor/capacitor
network. Resistor and capacitor values vary depending upon the
standard. Today the most internationally recognized ESD standard
is IEC 61000-4-2. IEC 61000-4-2 is a system level standard used
by manufacturers to model ESD events from human contact. The
test is performed by discharging a 150pF capacitor through a
330Ω resistor. Discharge into the equipment may be through direct
contact (contact discharge) or just prior to contact (air discharge).
Ipeak
I
100%
ESD Discharge Levels per IEC61000-4-2
90%
I at 30 ns
I at 60 ns
10%
Level
Test Voltage
Air Discharge
(kV)
Test Voltage
Contact Discharge
(kV)
First
Peak
Current
(A)
Peak
Current
at 30 ns
(A)
Peak
Current
at 60 ns
(A)
1
2
2
7.5
4
2
2
4
4
15
8
4
3
8
6
22.5
12
6
4
15
8
30
16
8
t
30 ns
60 ns
tr = 0.7 to 1 ns
ESD Waveform per IEC 61000-42
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
6
Introduction & Background
Computer & Digital Video Protection
ESD Immunity: System Level vs. Device Level
Cable Discharge
For ESD immunity, it is important to distinguish between system
level immunity and device level immunity. The JEDEC JESD22A114E which is equivalent to the earlier Mil-Std-883 is a device
level standard appropriate for the level of ESD threat seen in the
manufacturing environment. The IEC 61000-4-2 standard is intended
to describe the level of ESD threat seen in the system environment.
In the case of transceiver ICs, most are rated to 2kV Human Body
Model (HBM) according to the JEDEC Standard/Mil-Std 883. This
is not the same as 2kV for the system level standard (IEC 61000-42). In fact, the IEC pulse, for a given voltage level, will render over
5 times higher current levels than the JEDEC standard. The chart
illustrates this difference: a 2kV ESD pulse for the Mil-Std 883
renders a peak current of approximately 1.33A. For the system level,
that same 2kV charge level corresponds to a peak current of 7.5A.
Cable Discharge (or CDE) is a real and frequent phenomenon in the
Ethernet environment. CDE can be viewed as a type of electrostatic
discharge, but should be treated as a separate transient event from
ESD. An Ethernet cable, generally unshielded Cat-5 or Cat-6 twisted
pair, can be modeled as a capacitor element capable of storing
significant charge build up. As defined in the IEEE 802.3 standard,
an Ethernet cable can be as long as 100m. The cable becomes
charged by means of triboelectric charging or induction. Since Cat5 and Cat-6 twisted pair cables exhibit very low leakage properties,
the charge stored on the cable can remain on the twisted pair for
up to several hours before discharging to the port during a plug
event. This frequently poses a particularly dangerous threat to
Ethernet ports. The high peak voltage and current of the CDE can
cause the Ethernet transceiver to become overstressed resulting in
intermittent malfunctions. In many cases, the transceiver can also
fail catastrophically.
Peak Current IEC vs JEDEC
IEC Level
(Contact discharge)
ESD
Voltage
(kV)
JEDEC JESD-A114E
Ipp (kV)
IEC 61000-4-2
Ipp (A)
1
2
1.33
7.5
2
4
2.67
15
3
6
4.00
22.5
4
8
5.33
30
ESD Immunity Standards: IEC61000-4-2 vs. JESD22-A114E
To achieve high system level ESD immunity, you should adhere
to the IEC 61000-4-2 standard. The IEC standard is more closely
representative of the real world ESD threats seen by electronic
systems. Most commercial designs require passing minimum of
±8kV for the Human Body Model of IEC (level 4) contact discharge.
Lightning
Interfaces connected to the telecommunications network are exposed
to lightning surges. Electromagnetic coupling of lightning energy can
induce large transient pulses in nearby telecommunications lines.
Lightning, or surge transients, are sometimes described as “slow”
transients because unlike the fast, nanosecond rise times of ESD
and Cable Discharge, a lightning pulse is generally on the order of
microseconds in duration. However, the energy contained within
the pulse is orders of magnitude higher, posing a destructive risk to
telecommunications equipment.
The EMC community models surge transients using a combinational
waveform which describes the basic surge wave shape and
characteristics: rise time duration, fall time duration, and peak
pulse current (Ipp) or peak pulse voltage. The lightning waveform
can be either characterized as a voltage waveform with respect
to time or a current waveform with respect to time. For example, the
IEC 61000-4-5 calls for a 25A 8x20µs waveform. This waveform
represents a pulse of 20µs in duration from t=0 to the 50% decay
point. The rise time is 8µs to the peak pulse current (Ipp), 25A in this
case (see figure below).
Figure 4 – IEC 61000-4-5 Current Impulse
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
7
Introduction & Background
Computer & Digital Video Protection
TVS Basics
Transient Voltage Suppressor (TVS) diodes have long been used
to provide robust circuit protection. As shown in the following
diagram, TVS diodes are generally connected as shunt elements
across a transmission line. Under normal operating conditions
the TVS diode presents a high impedance to the protected circuit.
During a transient event, the TVS achieves breakdown, presents
a low impedance shunt path, and the transient current is shunted
through the TVS diode. A good TVS protection circuit must divert
transient current and clamp transient voltage below the failure
threshold of the protected IC.
I (Amps)
Transient Voltage Suppression (TVS) Diodes
2.5 V
Vrwm
Vclamp
V (Volts)
Typical 5V TVS IV Curve
Semtech Low Vrwm IV Curve
IV Curve for Semtech Low Working Voltage Process
Voltage
ESD Event
Transient
Enviroment
Zin
TVS
Diode
Protected
Circuit
TVS Diode Operation
Parameters for Effective Circuit Protection
A good TVS device for protecting dataline communications
interfaces must have some key parameters. First, low working
voltage is a critical TVS parameter for safeguarding submicron
integrated circuits. The working voltage, or Vrwm, is the maximum
rated DC voltage for the TVS device. At the Vrwm voltage, the TVS
is still a non-conducting device. Once the transient voltage rises
above the working voltage, the TVS quickly achieves breakdown
and presents a low impedance path to divert the transient. Thus,
a low working voltage is essential for clamping a transient to
a level well below the damage threshold of the IC that the TVS
is protecting. The I-V curve illustrates the advantage of a lower
working voltage. The green line represents a typical I-V curve
for a standard TVS device while the red I-V curve illustrates the
Semtech’s low working voltage technology. The lower working
voltage means the transient voltage is arrested more quickly and
thus can be clamped to a lower voltage. Using TVS devices with
lower working voltage is critical to reducing the stress energy seen
by the communications transceiver. To address this need, Semtech
has designed a family of 2.5V working voltage protection devices
for safeguarding next generation high-speed transceivers.
Protection Design Guide
Secondly, the TVS should present low capacitance to preserve
signal integrity on the high-speed interface. If the capacitance of
the TVS diodes is too high, adding excessive loading to the circuit,
signal distortion and data errors will result.
Finally, the TVS needs to offer high-surge handling. For systems
in the communications infrastructure, components rated only
for ESD transient levels will not provide sufficient protection. The
TVS component must also be able to handle the higher energy
contained within cable discharges and the variety of lightning
threats common to Ethernet interfaces. As a general guideline,
the TVS should at least provide 25A of surge handling for an 8x20
microsecond pulse.
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
8
Introduction & Background
Computer & Digital Video Protection
Clamping Voltage
Clamping voltage, by definition, is the maximum voltage drop across
the protection device during a transient event, which is also the stress
voltage seen by the protected IC. The clamping voltage is the most
critical parameter to consider when choosing a TVS device.
It is important to note that a device rated at IEC 61000-4-2 does
not guarantee the system will pass ESD testing. This is because
the IEC is a system level standard that was originally intended to be
applied as pass/fail criteria for showing system level ESD immunity.
The purpose of a protection device is to reduce a transient voltage
spike down to a safe voltage for the protected IC, and the best way to
insure that your TVS protection device adequately protects your interface
circuitry is by choosing components that offer the lowest clamping
voltage performance.
To illustrate the unique protection benefits of Semtech’s proprietary
EPD technology, the following chart compares the clamping
voltage of an industry standard 5V TVS device with the clamping
voltage of the Semtech RClamp2504N device. Built on the EPD
platform, the RClamp2504N offers a very low 2.5V working voltage.
Notice that the Semtech RClamp2504N provides a nice low, flat
clamping voltage over a wide range of peak pulse current values.
As a 2.5V working voltage device, the clamping performance of
the RClamp2504N is significantly lower than the typical 5V TVS
protection device. As the sensitivity on next generation PHYs
increases, selecting TVS devices with a lower clamping voltage
as illustrated in the chart can impact the difference between
safeguarding an Ethernet PHY or resulting in catastrophic damage.
Clamping Voltage vs Peak Pulse Current
Clamping Voltage - Vc (V)
30
Waveform
Parameters:
tr = 8µs
td = 20µs
25
20
Typical 5V
ESD Protection
15
10
Semtech
RClamp 2504N
5
0
0
5
10
15
20
25
30
Peak Pulse Current - Ipp (A)
Clamping Performance for RClamp 2504N
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
9
Introduction & Background
Computer & Digital Video Protection
Layout Guidelines
PC board layout is an important part of transient immunity design.
This is especially critical in computer and digital video applications,
where protecting the constant threat of ESD and CDE from normal
use is further complicated by the high speed of the link rates.
Parasitic inductance in the protection path can result in significant
voltage overshoot and may exceed the damage threshold of the
protected IC. This is especially critical in the case of fast rise-time
transients such as ESD or EFT. Recall that the voltage developed
across an inductive load is proportional to the time rate of change
in current (V = L di/dt). An ESD induced transient reaches a peak in
less than 1ns (per IEC 61000-4-2). Assuming a trace inductance of
20nH per inch and a quarter inch trace, the voltage overshoot will
be 50 volts for a 10A pulse.
inductive paths must be considered including the ground return
path, the path between the TVS and the protected line, and the
path from the connector to the TVS device. Additionally, The TVS
device should be placed as close to the entry point of ESD as
possible to reduce transient coupling into nearby traces.
The secondary effects of radiated emissions can cause upset
to other areas of the board even if there is no direct path to the
connector. Long signal traces will act as antennas to receive energy
from fields that are produced by the ESD pulse. By keeping line
lengths as short as possible, the efficiency of the line to act as an
antenna for ESD related fields is reduced. Minimize interconnecting
line lengths by placing devices with the most interconnects as close
together as possible. Finally, avoid running critical signal lines near
board edges or next to protected lines.
The primary rule of thumb is to minimize the effects of parasitic
inductance by making the shunt paths as short as possible. All
Vcc
Vcc
L1
Protected
IC
GND
Vp1 = L1 * di/dt
Vc = Clamping Voltage of TVS
L2
Vtotal = Vc + Vp1 + Vp2
Vp2 = L2 * di/dt
* L1 represents the parasitic inductance of the trace between TVS and Vcc
* L2 represents the parasitic inductance of the trace between TVS and GND
* Vtotal represents the voltage that will be see between Vcc and GND of the IC during a transicent.
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
10
Parts & Features
Computer & Digital Video Protection
Parts & Features
High-speed data transmission interfaces such as HDMI, DisplayPort and USB
are widely adopted on computer and consumer electronics systems. Semtech’s
industry leading low-clamping voltage, low capacitance, and innovative packaging
provide advanced performance solutions to safeguard your systems from transient
voltage threats. This section will highlight some of the newly released key computer
& digital video devices within the Semtech protection portfolio.
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
11
Parts & Features
Computer & Digital Video Protection
Part Number
Lines
Vrwm
Cap I/O to
I/O (typ)
Ipp max
(8x20μs) Application
RClamp0544T
4
5V
0.3pF
5A
HDMI
DisplayPort
LVDS
Circuit Diagram
2.0 x 1.0 x 0.4 mm
RClamp0544T
RClamp0522T
2
5V
0.3pF
5A
HDMI 1.3/1.4
DisplayPort
LVDS
USB 2.0
1.6 x 1.0 x 0.4 mm
RClamp0522T
RClamp0854P
3
1
5.5V
5.5V
0.5pF
max
3A
16A
USB 2.0
VBUS
1.6 x 1.6 x 0.6 mm
RClamp0854P
EClamp2410P
6
5V
-
-
MicroSD
4.0 x 1.6 x 0.58 mm
RClamp2504N
4
2.5V
2pF
25A
1000BASE-T
100BASE-T
LVDS
2.6 x 2.6 x 0.6 mm
RClamp2504N
RClamp3304N
4
3.3V
2pF
25A
1000BASE-T
100BASE-T
LVDS
2.6 x 2.6 x 0.6 mm
RClamp2504N
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
12
Parts & Features
Computer & Digital Video Protection
Part Number
RClamp2504P
Lines
4
Vrwm
2.5V
Cap I/O to
I/O
0.4pF
Ipp max
(8x20μs) Application
5A
1000BASE-T
100BASE-T
LVDS
Multimedia Card
Circuit Diagram
1.6 x 1.6 x 0.6 mm
RClamp3304P
4
3.3V
0.4pF
5A
1000BASE-T
100BASE-T
LVDS
Multimedia Card
1.6 x 1.6 x 0.6 mm
SR12
2
12V
3pF
16A
xDSL
2.9 x 2.37 x 1.0 mm
EClamp2422N
2
5V
-
-
Audio
1.45 x 1.0 x 0.58 mm
RClamp0531T
1
5V
0.5pF
4A
Antenna
1.0 x 0.6 x 0.4 mm
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
13
Protection Solutions
Computer & Digital Video Protection
RClamp® 0544T
ESD Protection for HDMI and other High Speed Interfaces
The RClamp0544T is a 4-line protection device operating at 5V.
It has a typical capacitance of only 0.30pF between I/O pins.
This allows it to be used on circuits operating in excess of 3GHz
without signal attenuation. They may be used to ESD immunity
requirements of IEC 61000-4-2, Level 4 (±15kV air, ±8kV contact
discharge).
Features
•
•
•
•
•
•
•
5V working voltage
4-line protection
Capacitance: typical 0.3pF Line-to-Line
Low-clamping voltage
No impedance matching required
No Insertion loss up to 3.0 GHz
Ultra-small leadless package (2.0 x 1.0 x 0.4 mm)
The RClamp0544T is in a 8-pin, RoHS/WEEE compliant,
SLP2010P8T package. It measures 2.0 x 1.0 x 0.4 mm. The leads
are spaced at a pitch of 0.4mm and are designed for easy PCB
layout by allowing the traces to run straight through the device.
Applications
•
•
•
•
•
Description
Mini HDMI
HDMI 1.3 / 1.4
LVDS
DisplayPort
USB 2.0
RClamp0544T
RClamp0544T
Data 2+
Data 2-
High performance, ultra low
capacitance ESD protection for
maximum signal integrity in a flow
through package.
Data 1+
Data 1-
To HDMI
Graphics Chip
Data 0+
HDMI
Connector
Data 0-
CLK +
CLK RClamp0544T (3 Each)
CEC
SCL
SDA
HP Detect
5V Power
GND
Protection for HDMI Interface
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
14
Protection Solutions
Computer & Digital Video Protection
RClamp® 0522T
Description
ESD Protection for USB 2.0 and other
High Speed Interfaces
The RClamp0522T has typical capacitance of only 0.3pF (line-toline). This means it can be used on circuits operating in excess of
3GHz without signal attenuation. They may be used to meet the
ESD immunity requirements of IEC 61000-4-2, Level 4 (±15kV air,
±8kV contact discharge). Each device can be configured to protect
1 bidirectional line or two unidirectional lines.
Features
•
•
•
•
•
•
5V working voltage
2-line protection
Capacitance: typical 0.3pF Line-to-Line
Low-clamping voltage
No insertion loss up to 3.0 GHz
Small leadless package (1.6 x 1.0 x 0.4 mm)
The RClamp0522T is in a 6-pin SLP1610P4T package. It measures
1.6 x 1.0 x 0.4 mm. The leads are spaced at a pitch of 0.5 mm and
are finished with lead-free NiPdAu. They are designed for easy PCB
layout by allowing the traces to run straight through the device.
Applications
•
•
•
•
USB 2.0
HDMI 1.3 / 1.4
LVDS
DisplayPort
RClamp0522T
RClamp0522T
RClamp0522T flow through design
is optimized for next generation high
speed interfaces. Ultra low capacitance
maintains maximum signal integrity.
USB Connector
USB Controller
Vbus
D-
D-
D+
D+
RClamp0522T
Gnd
Protection for USB 2.0 Interfaces
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
15
Protection Solutions
Computer & Digital Video Protection
RClamp® 0854P
Description
ESD Protection for USB 2.0 with
Integrated 5V VBus Protection
Features
•
•
•
•
•
•
•
Protects three I/O lines operating up to 5.5V
Protects one Vbus line operating up to 5.5V
Capacitance: typical 0.8pF line-to-ground
Low clamping voltage
No insertion loss up to 2.0GHz
Large ground for increased ESD performance
Small package (1.6 x 1.6 x 0.6 mm)
Applications
•
•
USB 2.0
USB OTG
The RClamp0854P is specifically designed to protect the USB
port. The unique design of this device features low capacitance
TVS diodes for protection of the USB data (DP, DM) and USB ID
pins operating up to 5.5 volts. Loading capacitance on these lines
is <1pF for maximum signal integrity. An integrated 5.5 volt TVS
diode is used for protection of the USB voltage bus, which ensures
isolation between power and data lines. Leakage current of the
Vbus protection is <50nA when operating at 5.5 volts.
The RClamp0854P is in a 6-pin, RoHS compliant, SLP1616P6
package. It measures 1.6 x 1.6 x 0.6 mm. The leads are spaced at
a pitch of 0.5 mm and are finished with lead-free NiPdAu. They may
be used to meet the ESD immunity requirements of IEC61000-4-2,
Level 4 (15kV air, 8kV contact discharge).
RClamp0854P
RClamp0854P
Separate TVS for VBus protection ensures
isolation between power and data lines.
5
4
3
2
1
RClamp0854P
VBus
DM
DP
USB ID
GND
USB
GND
Protection for USB 2.0 Interface
RClamp0854P
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
16
Protection Solutions
Computer & Digital Video Protection
EClamp® 2410P
Description
ESD/EMI Protection for Multimedia Cards
The EClamp2410P is a combination EMI filter and line termination
device with integrated TVS diodes for use on Multimedia Card
Interfaces. They have been optimized for protection of T-Flash/
MicroSD interfaces in cellular phones and other portable devices.
The device consists of six circuits that include series impedance
matching resistors and pull up resistors as required by the SD
specification. TVS diodes are included on each line for ESD protection.
Features
•
•
•
•
•
•
5V working voltage
Protection & termination for six lines & Vdd
Capacitance: typical 12pF per line
Termination resistors: 45Ω
Pull up resistors: 15kΩ (3 each) and 50kΩ
16 Pin leadless package (4.0 x 1.6 x 0.58 mm)
An additional TVS diode connection is included for protection
of the voltage (Vdd) bus. Termination resistor value of 45kΩ is
included on the DAT0, DAT1, DAT2, DAT3, CMD, and CLK lines. Pull
up resistors of 15kΩ are included on DAT0, DAT1, DAT 2, and CMD
lines while a 50kkΩ pull up resistors included on the DAT3 line.
These may be configured for devices operating in SD or SPI mode.
Applications
•
•
T-Flash / MircoSD interfaces
MMC interfaces
EClamp2410P
µSD protection with integrated EMI/TVS
protection saving valuable PCB board space.
DAT 1 IN
1 16
DAT 0 IN
Vss
DAT 1 OUT
DAT 0 OUT
CLK IN
CLK OUT
Rup 15Ku1
Rup 15Ku1
V DD
Rup 50Ku1
CMD IN
CMD OUT
DAT 3 IN
DAT 3 OUT
DAT 2 IN
DAT 2 OUT
HOST IC
Protection for MicroSD Interface
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
17
Protection Solutions
Computer & Digital Video Protection
RClamp® 2504N
Description
ESD & Surge Protection for 1000BASE-T
(Gigabit Ethernet) Interfaces
The RClamp2504N uses Semtech’s Enhanced Punch-Through
Diode (EPD) technology process to achieve a low working voltage
of 2.5 volts. The low working voltage enables superior clamping
voltage performance for safeguarding submicron silicon PHY
architectures.
Features
•
•
•
•
•
2.5V working voltage*
4-line protection
Low-clamping voltage
25A (8x20μs) surge rating
Very small package (2.6 x 2.6 x 0.6 mm)
The 4-line RClamp2504N can be configured to meet the intrabuilding surge requirements of Telcordia GR-1089. The low
clamping voltage and high surge rating of this device also make
it an ideal part for protecting against dangerous ESD and cable
discharge threats. The RClamp2504N presents minimal line-to-line
capacitance for preserving signal integrity and is housed in a small
leadless, RoHS compliant package.
Applications
•
•
•
Gigabit Ethernet
10/100 Ethernet
LVDS
The 2.5V working voltage (Vrwm) means that
the TVS can achieve breakdown quickly during a
transient event. Next generation PHYs are best
protected by 2.5V working voltage TVS.
RClamp2504N
RClamp2504N
TP1+
RClamp2504N
TP1-
RJ-45
TP2+
1
2
3
4
5
6
7
8
RClamp2504N
TP2-
Ethernet
PHY
TP3+
RClamp2504N
TP3-
TP4+
RClamp2504N
TP4-
Protection for Gigabit Ethernet Interface
* RClamp© 3304N is footprint compatible, but with 3.3V Vrwm
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
18
Protection Solutions
Computer & Digital Video Protection
RClamp® 2504P
Description
ESD & Cable Discharge Protection for
High-Density Ethernet Interfaces
The RClamp2504P is a 4-line, 2.5V (Vrwm) low capacitance
protection array for safeguarding Ethernet interfaces from ESD and
Cable Discharge transients. The innovative design incorporates
surge rated, low capacitance steering diodes and a TVS diode
in a single package. Each line has a maximum capacitance of <
0.8pF line to ground. The capacitance of each line is well matched
for consistent signal balance. This device is optimized for ESD
protection of sensitive electronics. It may be used to meet the ESD
immunity requirements of IEC 61000-4-2, Level 4 (±15kV air, ±8kV
contact discharge).
Features
•
•
•
•
•
2.5V working voltage*
4 lines of protection
Low capacitance (<0.8pF)
Excellent ESD clamping
Ultra-small package (1.6 x 1.6 x 0.6 mm)
Applications
•
•
•
1000BASE-T ethernet
100BASE-T ethernet
Multimedia card interfaces
RClamp2504P
RClamp2504P
Ultra-small, 4-line RClamp2504P provides
superior fast transient clamping performance
with minimal part footprint.
TPA+
TPA-
RClamp2504P
RJ-45
TPB+
TPB-
Ethernet
PHY
TPC+
TPC-
RClamp2504P
TPD+
TPD-
Protection for High-Density Ethernet Interface
* RClamp© 3304P is footprint compatible, but with 3.3V Vrwm
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
19
Protection Solutions
Computer & Digital Video Protection
SR12
ESD & Surge Protection for ADSL & VDSL Interfaces
The unique design of the SR12 incorporates four surge rated, low
capacitance steering diodes and a TVS diodes 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.
Features
•
•
•
•
Description
12V working voltage
2-line protection array
Low-clamping voltage
SOT-143 package (2.9 x 2.37 x 1.0 mm)
Applications
•
•
•
ADSL interfaces
VDSL interfaces
Industrial interfaces
SR12
The SR12 can protect an ADSL or VDSL
tip/ring pair, providing very low clamping
voltage and minimal capacitive load.
+Vref
Line Side
Protection
(Optional)
1
4
CODEC
2
3
+Vref
Protecting XDSL Interface with SR12
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
20
Protection Solutions
Computer & Digital Video Protection
EClamp® 2422N
ESD/EMI Protection for Audio Interfaces
Features
•
•
•
•
•
5V working voltage
Protection and filtering for two lines
Capacitors: 100pF (Typical VR=0v)
Inductor: 2nH (Typical)
Small leadless package (1.45 x 1.0 x 0.58 mm)
Description
The EClamp2422N is a (C-L-C) low pass filter array with integrated
TVS diodes. It is designed to suppress unwanted EMI/RFI signals
and provide ESD protection for audio interfaces. Two identical
circuits consisting of an inductor of 2nH and capacitor value of
100pF, which are used to achieve 10dB minimum attenuation from
800MHz to 2.7GHz. It has a very low series resistance of 2.OΩ,
making it ideal for use on speaker/microphone interfaces.
Applications
•
•
Speaker ports
Microphone ports
EClamp2422N
Flow through design allows for efficient PCB layout.
Integrated low pass filter reduces part count.
V2
Vin +
V1
Vin −
Protection of Single-Ended Mode Microphone
with Speaker Output
Protection Design Guide
Differential Mode Protection with Speaker Output
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
21
Protection Solutions
Computer & Digital Video Protection
RClamp® 0531T
ESD Protection for Low Frequency Antenna
Description
Features
The RClamp0531T is a bidirectional single line protection device
offering a maximum capacitance of 0.80pF. This allows it to be
used on circuits operating in excess of 2.5GHz without signal
attenuation. They may be used to meet the ESD immunity
requirements of IEC 61000-4-2, Level 4.
•
•
•
•
•
•
5V working voltage
1-line bidirectional
Capacitance: typical 0.5pF
Low clamping voltage
No insertion loss up to 2.5GHz
Ultra small package (1.0 x 0.6 x 0.4 mm)
This device is packaged in a 2-pin, RoHS/WEEE compliance,
SLP1006P2T package measuring 1.0 x 0.6 x 0.4 mm. Each device
protects one high-speed line operating at 5 volts. It gives the
designer the flexibility to protect single lines in applications where
arrays are not practical.
Applications
•
•
•
•
GPS antennas
FM antennas
LVDS
High speed data lines
RClamp0531T
Ultra low capacitance RClamp0531T featuring
superior clamping performance protecting
today’s sensitive IC’s.
ESD Sensitive
Circuit
High speed single line ESD protection
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
22
Applications
Computer & Digital Video Protection
Circuit Protection Applications
As high speed interfaces can be subject to wide variety of transient conditions
and operating environments, the need for good circuit protection solutions
are often unique to the application. This section will examine in deeper
detail some of the more subtle aspects of protecting circuit interfaces from
overvoltage threats.
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
23
Applications
Computer & Digital Video Protection
IEC 61000-4-x Transient Immunity Standards
The International Electrotechnical Commission (IEC), a worldwide
organization promoting international cooperation on questions
concerning standardization in electrical & electronic fields, has
developed transient immunity standards which have become
minimum requirements for manufacturers wanting to do business
in the European Community (EC).
The ESD threat is divided into four threat levels. Threat level 1 is
considered the least severe while threat level 4 is the most severe.
Most manufacturers will adhere to level 4: ±8kV contact discharge,
±15kV air discharge. IEC 61000-4-2 also specifies the ESD current
waveform and parameters shown in Figure 1 & Table 1.
Ipeak
I
100%
Three of the IEC standards deal with transient immunity:
• IEC 61000-4-2 : Electrostatic Discharge (ESD)
• IEC 61000-4-4 : Electrical Fast Transient/Burst
(Electrical Fast Transients)
• IEC 61000-4-5 : Surge Immunity
90%
I at 30 ns
The following sections provide a summary of each of the transient
immunity standards.
I at 60 ns
10%
IEC 61000-4-2 – Electrical Discharge (ESD)
Standard
IEC 61000-4-2 addresses one of the most common forms of
transients in electronic systems: Electrostatic discharge (ESD). ESD
results from conditions which allow the build up of electrical charge
from contact and separation of two non-conductive materials.
When the charged body is brought in proximity of another object
of lower potential, energy is released in the form of electrostatic
discharge.
The standard defines immunity requirements for ESD which can
be coupled into the equipment directly or through radiated effects.
Direct coupling includes any user accessible entry points such
as I/O ports, switches, computer keyboards, panel displays, and
equipment housings. Radiated coupling results from the discharge
between two bodies which are external to the system.
Because the human body is one of the most common generators
of ESD, the IEC standard defines a test set up which is designed
to simulate an ESD event from a human body. The “Human
Body Model” (HBM) as it is referred to, is considered a valid
representation of worst case ESD stresses. Discharge into
equipment may be through direct contact (contact discharge
method) or just prior to contact (air discharge method). Contact
discharge is the preferred test method, but air discharge is used
where contact discharge cannot be applied.
t
30 ns
60 ns
tr = 0.7 to 1 ns
Figure 1 - ESD Waveform per IEC 61000-42
The rise time is extremely fast, defined as 0.7 to 1ns, with a second
peak at 30ns and a total duration of only 60ns. The total energy
contained within the pulse is approximately a few hundred
microjoules.
Transient Voltage Suppression (TVS) diodes are an ideal choice
for meeting the ESD transient immunity requirements of IEC
61000-4-2 and are proven solutions for suppressing system level
ESD events. The extremely fast response time of the TVS diode
is essential for responding to the 1ns rise time of the ESD pulse.
Additionally, TVS diodes are capable of clamping the incoming
transient to a low enough level as not to cause damage to the
protected semiconductor. All TVS diode devices and families
offered by Semtech may be used to suppress ESD to level 4 of IEC
61000-4-2. The fast response and low clamping levels make TVS
diodes suitable for ESD suppression on data and I/O ports.
Level
Indicated
Voltage
First peak
current of
discharge
+/- 10%
Rise time
(tr) with
discharge
switch
Current
(+/- 30%
at 30 ns)
Current
(+/- 30%
at 60 ns)
kV
A
ns
A
A
1
2
7.5
0.7 to 1
4
2
2
4
15
0.7 to 1
8
4
3
6
22.5
0.7 to 1
12
6
4
8
30
0.7 to 1
16
8
Table 1 – IEC61000-4-2 Waveform Parameters
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
24
Applications
Computer & Digital Video Protection
IEC 61000-4-4 – Electrical Fast Transients (EFT)
Immunity Standard
Electrical fast transients occur as a result of arcing contacts in
switches and relays. EFT disturbances are common in industrial
environments where electromechanical switches are used to
connect and disconnect inductive loads. IEC 61000-4-4 specifies
the EFT threat in both power and data lines. The electrical fast
transient is described in terms of a voltage across a 50Ω load from
a generator having a nominal dynamic source impedance of 50Ω.
The output occurs as a burst of high voltage spikes at a repetition
rate ranging from 2kHz to 5kHz. The burst length is defined as
15ms with bursts repeated every 300ms.
Each individual burst pulse is a double exponential waveform
with a rise time of 5ns and a total duration of 50ns. A diagram
showing the EFT waveform and the EFT burst repetition rate and
burst period is shown in Figure 2. Four severity levels are defined
in terms of an open circuit voltage as a function of installation
environment.
Figure 2 – EFT Burst
Additionally, the extremely fast response time of TVS diodes is essential
for responding to the 5ns rise time of the EFT pulse. Due to the
repetitive nature of the EFT pulses, TVS diodes with slightly higher
power handling capability will be required for protection at threat level 4.
Peak Amplitude
Level
Power Supply Port
I/O Signal, Data & Control Lines
VOC (kV)
ISC (A)
VOC (kV)
ISC (A)
1
0.5
10
0.25
5
2
1
20
0.5
10
3
2
40
1
20
4
4
80
2
40
Table 2 – IEC61000-4-4 Severity Levels
IEC 61000-4-5 – Surge Standard
IEC 61000-4-5 addresses the most severe transient conditions on
both power and data lines. These are transients caused by lightning
strikes and switching. Switching transients may be the result
of power system switching, load changes in power distribution
systems, or short circuit fault conditions. Lightning transients may
result from a direct strike or induced voltages and currents due to
an indirect strike. The IEC 61000-4-5 standard defines a transient
entry point and a set of installation conditions. The transient is
defined in terms of a generator producing a given waveform and
having a specified open circuit voltage and source impedance. Two
surge waveforms are specified : The 1.2 x 50μs open-circuit voltage
waveform and the 8 x 20μs short-circuit current waveform (Figures
3 & 4 respectively).
The installation environments are defined as :
1 - Well Protected
2 - Protected
3 - Typical Industrial
4 - Severe Industrial
Table 2 provides the open-circuit voltages for each threat level and
for both power supply and data lines. Short circuit current values
are estimated by dividing the EFT open-circuit voltage by its 50Ω
source impedance. This represents the worse case stresses seen
by the suppression element. Like ESD, EFT can be especially fatal
on data and I/O lines. The fast rise time of the EFT pulses demands
a suppression element with the same characteristics as that which
are required for suppression of an ESD pulse. Again TVS diodes
offer the best solution for suppressing the expected transient
energy while keeping clamping voltages across the protected
elements to a minimum.
Figure 3 – IEC 61000-4-5 Voltage Impulse
Figure 4 – IEC 61000-4-5 Current Impulse
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
25
Applications
Computer & Digital Video Protection
circuit voltages by the source impedances. The short-circuit current
values are more useful in choosing a suppression element.
The short circuit current stress levels are defined with the 8 x
20μs waveform for power supply applications with a 2Ω source
impedance. For data lines requiring a 42Ω source impedance,
the short-circuit current waveform is defined as 8 x 20μs. For
telecommunications applications, the open-circuit voltage is
defined as 10 x 700μs and the short-circuit current is a 5 x 300μs
waveform. The source impedance is given as 40Ω.
Transient stress levels for each entry point into the system are
defined by installation class. The six classes are defined as :
Class 0 : Well protected environment
Class 1 : Partially protected environment
Class 2 : Well separated cables
Class 3 : Cables run in parallel
Class 4 : Multi-wire cables for both electronic & electrical circuits
Class 5 : Connection to telecommunications cables
and overhead power lines (Low density populated areas)
The type of suppression element needed for IEC 61000- 4-5
class surges depends upon the threat level and installation class.
For power supply applications high power devices are required.
A discrete device or an assembly may be required depending
on the application. TVS diodes are the best choice for data line
applications and secondary board level protection because of their
superior clamping voltage characteristics and fast response time.
A class 0 environment is considered the lowest threat level and has
no transient stress requirements. The class 5 environment is the
most severe and requires the highest transient stress level testing.
Table 3 summarizes threat levels as a function of installation class.
Values of voltage stress using the 1.2 x 50μs waveform are given.
Corresponding current values are calculated by dividing the open-
Class
0
1
2
3
4
5
WAVE
FORMS
Voltage
Current
Power Supply
Unsym Lines
(Long Distance Bus)
Sym Lines
Data Bus
(Short Distance)
Coupling Mode
Coupling Mode
Coupling Mode
Coupling Mode
Line-GDN
Zs =42 Ω
Line-GND
Zs = 42 Ω
0.5KV
1.0KV
(n/a)
12A
24A
Line-Line
Zs = 2 Ω
Line-GND
Zs = 12 Ω
Line-Line
Zs =42 Ω
Voltage
NO REQUIREMENT
Current
Voltage
Line-GDN
Zs =42 Ω
(n/a)
0.5KV
Current
(n/a)
42A
Voltage
0.5KV
1.0KV
0.5KV
1.0KV
1.0KV
0.5KV
Current
250A
83A
12A
24A
24A
12A
Voltage
1.0KV
2.0KV
1.0KV
2.0KV
2.0KV
(n/a)
Current
500A
167A
24A
48A
48A
Voltage
2.0KV
4.0KV
2.0KV
4.0KV
(n/a)
(n/a)
Current
1KA
333A
48A
95A
Voltage
(Note 1)
(Note 1)
2.0KV
4.0KV
48A
95A
95A
Voltage
(1.2 x 50µs)
(1.2 x 50µs)
(1.2 x 50µs)
(1.2 x 50µs)
(1.2 x 50µs)
(1.2 x 50µs)
Current
(8 x 20µs)
(8 x 20µs)
(8 x 20µs)
(8 x 20µs)
(8 x 20µs)
(8 x 20µs)
Current
4.0KV
Note 1: Depends on class of local power supply system.
Table 3 – IEC61000-4-5 Severity Levels
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
26
Applications
Computer & Digital Video Protection
Summary
Any OEM equipment manufacturer who plans to sell in the
European market will have to meet the requirements of IEC
61000-4. IEC defines three transient immunity standards which
provide equipment suppliers with a susceptibility level. Designing in
accordance to the IEC standard enables manufacturers to produce
more reliable products. Each of the transient immunity standards
defines transient sources, entry paths into a system, severity levels,
and test methods. Equipment application will determine what level of
transient protection is needed. Transient suppression devices must
be carefully chosen for each of the standards.
References
Makowski, Leo P., “IEC 1000-4-X (801) Series of Standards,” EMC
Test & Design, October 1994 Clark, O.M., “Electrical-Transient
Immunity: A Growing Imperative for System Design,” Electronic
Design, January 23, 1992
IEC Publication 1000-4-2 “Electromagnetic Compatibility for
Industrial Process Measurement and Control Equipment Part 4, Electrostatic Discharge Requirements,” International
Electromechanical Commission, 1995
IEC Publication 1000-4-4 “Electromagnetic Compatibility for
Industrial Process Measurement and Control Equipment - Part
4, Electrical Fast Transient/ Burst Requirements,” International
Electromechanical Commission, 1995
IEC Publication 1000-4-5 “Electromagnetic Compatibility for
Industrial Process Measurement and Control Equipment - Part
4, Surge Immunity Test,” International Electromechanical
Commission, 1995
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
27
Applications
Computer & Digital Video Protection
ESD Protection Solutions for DisplayPort
The DisplayPort standard is an uncompressed, open digital
communication interface that represents a cost reduction
opportunity for PC makers by consolidating the internal and
external interconnect. When used internally, it is an interface
within a PC or monitor. Externally, it connects a PC to a monitor
or projector, or TV. When used as an external interface, the
DisplayPort plug is frequently exposed to Electrostatic Discharge
(ESD) directly from the user or Cable Discharge (CDE) from hot plug
cable.
To ensure proper functionality, DisplayPort-based systems must
protect all potentially exposed interface signals and power pins to
meet or exceed the EOS (electrical over stress) specification of IEC
61000-4-2, Level 4 (±15kV Air, ±8kV Contact) without damage.
In most cases, the on-chip ESD protection is no longer sufficient
to meet this EOS requirement, making off chip ESD protection
circuitry necessary. Providing external protection is further
complicated by the high-speed of the link rates; both 2.7Gbps and
1.62Gbps are supported in the standard. At such a high data rate,
signal integrity and impedance requirements are given more focus
than ever before, as put forth in the DisplayPort Compliant Test
Specification (CTS).
Protecting DisplayPort interface from ESD presents several
challenges. A low working voltage, and low clamping voltage device
is required to minimize stress on the protected IC during an ESD
event. At typical transmission speed of 2.7Gbps, an ultra low
capacitance ESD devices is necessary to maintain signal integrity.
Semtech’s RClamp0544T is the latest addition to the high speed
interface protection family. It provides reliable ESD protection in
excess of IEC 61000-4-2 Level 4, without the need for capacitive
compensation.
RClamp0544T responds quickly in an event of ESD and its low
clamping voltage ensures the stress voltage seen by sensitive ICs
are well below the destructive threshold.
RClamp0544T has a typical capacitance of 0.3pF between I/O pins
which allows it to be used on circuits operating in excess of 3GHz
without signal degradation. From a mechanical point of view, the
RClamp0544T is housed in a leadless SLP2010P8T package that
measures only 2.0 x 1.0 mm. Its unique design allows the traces to
run straight through the device thus simplifying PCB design.
1
DIFF100_TX0P_DP
3
DIFF100_TX0N_DP
DOP
DON
GND
DIFF100_TX1P_DP
DIFF100_TX1N_DP
4
D1P
6
D1N
RClamp0544T
7
DIFF100_TX2P_DP
9
DIFF100_TX2N_DP
D2P
D2N
GND
DIFF100_TX3P_DP
DIFF100_TX3N_DP
10
D3P
12
D3N
DisplayPort
Connector
RClamp0544T
15
DIFF100_AUXP_DP
V5
17
DIFF100_AUXN_DP
AUXP
AUXN
GND
18
HP_DET_9801_5V
20
F2
600 Ohm
500 mA
C79
10µF
HP_DET
PWR
RClamp0544T
Protection for DisplayPort Interface
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
28
Applications
Computer & Digital Video Protection
ESD Protection Solutions for HDMI
High Definition Multimedia Interface (HDMI) is an uncompressed,
all-digital audio/video interface. It provides a high speed interface
between audio/video source devices, such as DVD players, and
sink devices, such as digital displays. The HDMI plug is frequently
exposed to Electrostatic Discharge (ESD) directly from the user or
Cable Discharge (CDE) from hot plug cable.
To ensure proper functionality, HDMI-based systems must protect
all potentially exposed interface signals and power pins to meet or
exceed the EOS (electrical over stress) specification of IEC 610004-2, Level 4 (+/-15kV Air, +/-8kV Contact) without damage. Current
HDMI silicon runs at 2.25Gbps with 3.4Gbps in the near future. At
such a high data rate, signal integrity and impedance requirements
are given more focus than ever before, as put forth in the HDMI
Compliant Test Specification (CTS). The HDMI CTS requires all
HDMI sink devices to maintain the differential impedance of the
high speed lines at 100Ω ±15%.
Semtech’s RClamp0544T has a typical capacitance of 0.3pF
between I/O pins which allows it to be used on HDMI running at a
typical transmission speed of 2.25Gbps. Furthermore, this ultra low
capacitance eliminates the need to add capacitive compensation
while maintaining signal integrity.
From a mechanical point of view, the RClamp0544T is housed in
a leadless SLP2010P8T package that measures only 2.0 x 1.0
mm. Its unique design allows the traces to run straight through the
device further simplifying PCB design.
RClamp0544T features a very low clamping voltage and low turn
on voltage, which means RClamp0544T will respond quickly in
an event of ESD and instantly clamp the stress voltage seen by
sensitive ICs to well below the destructive threshold.
RClamp0544T provides reliable ESD protection in excess of IEC
61000-4-2 Level 4 (+/- 8kV Contact, +/-15kV Air) as well as
IEC61000-4-4 EFT(40A, 5/50ns) and IEC61000-4-5 lightning
(5A, 8/20us).
Data 2+
Data 2-
Data 1+
Data 1-
To HDMI
Graphics Chip
Data 0+
HDMI
Connector
Data 0-
CLK +
CLK RClamp0544T (3 Each)
CEC
SCL
SDA
HP Detect
5V Power
GND
Protection for HDMI Interface
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
29
Applications
Computer & Digital Video Protection
ESD Protection Solutions for LVDS
Low-voltage differential signaling (LVDS), is now pervasive in
communications networks and used extensively in applications
such as laptop computers, office imaging, industrial vision, test and
measurement, medical, and automotive. It provides an attractive
solution - A small-swing differential signal for fast data transfers at
significantly reduced power and with excellent noise immunity.
LVDS uses high-speed analog circuit technique to provide multigigabit data transfers on copper interconnects and is a generic
interface standard for high-speed data transmission. The American
National Standards Institute (ANSI)/Telecommunications Industry
Association (TIA)/Electronic Industries Alliances(EIA)-644-1995
standard specifies the physical layer as an electronic interface. It
recommends a maximum data rate of 655Mbits/s over twistedpair copper wire, but predicts a theoretical 1.9Gbits/s on an ideal
transmission medium.
LVDS
Transceiver
Semtech’s RClamp0544T is a 5V TVS array that offers low
capacitance and low clamping voltage, which makes it an ideal
solution for transmission speed of 500Mbps and above. The typical
differential mode capacitance of the Semtech RClamp0544T is
less than 0.3pF. The ultra low capacitance ensures that the signal
integrity will be maintained at 655Mbits/s, the maximum data
rate recommended, without the need for capacitive compensation.
Further more, RClamp0544T provides reliable ESD protection in
excess of IEC 61000-4-2 Level 4 (+/- 8kV Contact, +/-15kV Air)
as well as IEC61000-4-4 EFT(40A, 5/50ns) and IEC61000-4-5
lightning (5A, 8/20µs).
Regardless of the level of threat environment, Semtech’s RClamp0544T
responds quickly to an ESD event and its low clamping voltage
ensures the stress voltage seen by sensitive ICs are well below the
destructive threshold.
From a mechanical point of view, the RClamp0544T is housed in
a leadless SLP2010P8T package that measures only 2.0 x 1.0
mm. Its unique design allows the traces to run straight through the
device simplify PCB design.
RClamp0544T
RClamp0544T
Protection for LVDS Interface
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
30
Applications
Computer & Digital Video Protection
ESD Protection Solutions for USB
Semtech offers two options for USB2.0 protections depending on
whether VBUS protection is required.
USB stands for universal serial bus. It is the most successful
interface in the history of PC and has been virtually adopted 100%
in PC and peripherals.
Even though ESD protection requirement is not explicitly called out
in USB specifications, USB is susceptible to ESD as a hot insertion
and removal system. The high speed data transfer rate of 480Mbps
and ever increasing complexity of USB2.0 controllers make its
ESD protection quite a challenge. The variations between different
manufacturers further complicate the situation.
The selection criteria for protecting most advanced USB2.0 ports are:
1. Low capacitance for minimal signal degradation at 480Mbps
2. Fast response time and low turn on voltage to allow device
to turn on and limit the current going into protected IC in an
event of ESD
3. Low clamping voltage to limit the voltage across sensitive IC
4. Low leakage current for minimal power consumption
RClamp0542T:
• Provide one pair of high speed datalines with reliable ESD
protection in excess of IEC 61000-4-2 Level 4, without the
need for capacitive compensation
• Responds quickly in an event of ESD and its low clamping
voltage ensures the stress voltage seen by sensitive ICs is well
below the destructive threshold
• Has a typical capacitance of 0.3pF between I/O pins which
has minimum electrical effects on the high speed signal lines
and allows it to be used on circuits operating in excess of
3GHz without signal degradation
RClamp0854P:
• Offers Vbus protection as well as data line protection in excess
of IEC 61000-4-2 Level 4
• Has a separate TVS to protect VBus therefore provides
isolation between power and datalines
• Has a maximum capacitance of 0.5pF between I/O pins which
allows it to be used on circuits operating in excess of 3GHz
without signal degradation
USB Connector
5
RClamp0542T
4
3
USB Controller
2
Vbus
1
D-
D-
D+
D+
Gnd
Protection for USB 2.0 Interface
Protection Design Guide
RClamp0854P
VBus
DM
DP
USB ID
GND
USB
GND
Protection
for USB 2.0 Interface
RClamp0854P
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
31
Applications
Computer & Digital Video Protection
Transient Voltage Protection for
Gigabit Ethernet PHYs
Ethernet systems within the communications infrastructure are
subject to high-level transient threats. This type of equipment may
even need to meet the surge immunity requirements of Telcordia
GR-1089. Reliable protection of the Ethernet transceiver requires
a device that can absorb the expected transient energy, clamp the
incoming surge to a safe level, and yet remain transparent to the
system under normal operation. Additionally, each new generation
of Ethernet deployment yields higher-density boards that demand
protection solutions that occupy less board space. Exacerbating the
problem, Gigabit Ethernet systems must be rated to operate at high
temperatures, making application of external protection even more
challenging. This paper will discuss a solution for providing reliable
protection of GbE systems. This solution is designed to meet the
surge requirements of GR-1089. If designed properly, this solution
can be used without causing transmission errors.
Transient Threats
The small geometries of GbE transceivers make them particularly
susceptible to upset or damage from transient events. One of
the most common threats is a Cable Discharge Event (CDE). A
CDE occurs when an Ethernet cable becomes charged (due to
interaction with its environment) and subsequently discharges into
the circuit when the cable is plugged into the connector. In general,
the waveforms last for a few hundred nanoseconds with rapid
polarity changes. Electrostatic discharges (ESD) that originate
from the user are also common. These types of waveforms last for
approximately 60ns and are consistent with the human body model
as defined by immunity standards such as IEC 61000-4-2. For
outside connections, lightning can also induce high voltage surges
onto the communication lines that connect to the Ethernet PHY IC.
These events are high energy pulses, lasting several microseconds.
The Telcordia Technologies GR-1089-CORE specification defines a
set of requirements for lightning and ESD immunity for intra-building
equipment. The lightning tests are applied as metallic (line-to-line) or
longitudinal (line-to-ground) waveforms. The waveforms are defined
with a rise time of 2µs and a decay time of 10µs with an open
circuit (metallic) voltage of 800 volts short circuit current of 100A.
Positive and negative polarity surges are applied. To pass, the
equipment must continue to operate after the test.
Ethernet Magnetics
An Ethernet port includes transformers and common mode chokes
for connecting the PHY to the outside world. Transformers and
chokes can be discrete components, but integrated solutions that
include the RJ-45 connector, resistors and capacitors are becoming
increasingly popular. In either case, the transformer will provide a
high level of common mode isolation to external voltages, but no
protection for metallic surges. For a metallic (line-to-line) surge,
current will flow into one line, through the transformer and back
to the source. As the current flows, it charges the windings of the
transformer on the line side ( RJ45 side). Once the surge is removed,
the windings on the line side will stop charging and will transfer its
stored energy to the IC side where the PHY IC is located. Regardless,
the pulse will most certainly be destructive to the PHY chip.
TP1+
RClamp2504N
TP1-
RJ-45
1
2
3
4
5
6
7
8
TP2+
RClamp2504N
TP2-
Ethernet
PHY
TP3+
RClamp2504N
TP3-
TP4+
RClamp2504N
TP4-
Figure 1 - Protection for Gigabit Ethernet Interfaces
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
32
Applications
Computer & Digital Video Protection
Protection Solutions
GbE System Operation over Temperature
As the feature sizes on performance PHYs are scaling smaller along
with thinner oxide layers, using low working voltage TVS is critical
to safeguarding Ethernet PHYs. Semtech’s RClamp2504N is a low
capacitance, transient voltage suppressor (TVS) designed to protect
Gigabit Ethernet ports while maintaining traffic performance over
temperature. The RClamp2504N is constructed using Semtech’s
low-voltage EPD process technology to achieve a low working
voltage of 2.5 volts. The RClamp2504N circuit diagram is shown
in Figure 1. The device is in a leadless, RoHS compliant package
measuring 2.6 x 2.6 x 0.6 mm. The RClamp2504N’s low 2.5V
working voltage results in a low clamping voltage for maximum
protection of the GbE PHY. The RClamp2504N may be used on
the PHY side of the transformer to meet the Intra-building surge
requirements of Telcordia GR-1089 (Ipp=100A, tp=2/10µs).
Depending upon the operating environment, Telecom and Datacom
systems may be exposed to harsh temperatures extremes. Ethernet
ports within these systems are required to operate at very high
temperatures. In addition, the IEEE 802.3 specification requires
that the Ethernet interface supports data transmission on cable
lengths of up to 100 meters. A long cable length will present
an additional load to the system transmission, and at elevated
temperature, symbol or CRC (Cyclical Redundancy Check) errors
can result. Thus, an Ethernet protection circuit must provide the
clamping performance to arrest the GR-1089 surge, while also
residing on the Ethernet interface without introducing traffic errors.
5
1
9
3
7
Gnd
Figure 2 – RClamp2504N Circuit Diagram
Generally, the Ethernet interface should provide error free
transmission up to 65ºC with a 100m cable attached to the port.
This presents several challenges. First, the high temperature
means the margin of operation of the PHY will be reduced.
Secondly, the 100 meter cable presents a large load on the
receiving end. Finally, the protection component will present nonlinear impedance over temperature. The GbE PHY can account
for some impedance variations or discontinuities on the line
by performing a forward error correction (FEC). However, large
non-linear impedance changes across the differential pair can not
always be accounted. The amount of variation in the protection device
will depend on leakage current and capacitance; factors dictated
primarily by the junction area of the device.
Figure 1 illustrates a protection solution using the RClamp2504N
TVS device for protecting a gigabit ethernet PHY. The four line pairs
are protected using the RClamp2504N connected in differential
mode (line-to-line) on the PHY side of the transformer. For optimal
performance, parasitic inductance should be minimized by placing
the device as close to the magnetics as possible and on the same
side of the board as the PHY. The clamping voltage, measured at
10.8V, for a metallic mode 800V (100A) 2/10µs surge provides
sufficient clamping margin to minimize electrical stress and prevent
latent failure.
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
33
Applications
Computer & Digital Video Protection
Ethernet Traffic Test Data and Surge Results
The following data shows an example of traffic and surge performance
results using Semtech’s RClamp2504N TVS array per the circuit
diagram shown in Figure 1. The data was captured at elevated
temperature using a widely used four-port gigabit ethernet PHY in
a representative ethernet system. The multi-ports accessible on
the system board enabled using the loop back mode to send and
monitor signal data for error count monitoring. A traffic generation
evaluation board was used to generate, and transmit, pseudo
random Ethernet traffic. Temperature testing was initiated at room
temperature and was increased until frame errors were detected.
Traffic testing was performed over 100m of Cat 5/5e and Cat6
cable.
@ 25°C CRC/
Symbol Error
Table 1 records the results of the traffic testing. As shown, the
gigabit ethernet transmission with the RClamp2504N protection
scheme implemented showed no frame errors up to 75ºC across
100 meters of Cat 5 cable and up to 95ºC across 100 meters of
Cat 6 cable. Surge testing was also performed using the circuit
configuration shown in Figure 1. The results of the surge testing
are summarized in Table 2. As shown, the RClamp2504N protects
the PHY under test to Telecordia 2x10µs 100A and 1.2 x50µs 100A
surges and ITU K.21 10x700µs 25A surge.
Test
Circuit
Config
Cable Type
@ 65°C CRC/
Symbol Error
@ 75°C CRC/
Symbol Error
Traffic Test
Figure 1
Cat 5/5e
PASS
PASS
PASS
PASS
PASS
PASS
Traffic Test
Figure 1
Cat 6
PASS
PASS
PASS
PASS
PASS
PASS
IEEE Template
Figure 1
Cat 5/5e
PASS
IEEE Template
Figure 1
Cat 6
PASS
Table 1 - Summary of Traffic Results
Standard
Test
Current
Voltage
Circuit Config
Test Results
Telcordia
2x10µs
100A
800
Figure 1
PASS
Telcordia
1.2x50µs
100A
800
Figure 1
PASS
ITU K.21
10x700µs
25A
1000
Figure 1
PASS
Table 2 - Summary of Surge Test Results
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
34
Applications
Computer & Digital Video Protection
Safeguard Ethernet Interfaces from Cable
Discharge Threats
Protecting Ethernet interfaces from transient discharges can create
a challenge for engineers because good protection must meet two
criteria:
1. A protective device must effectively clamp a transient to a safe
voltage.
2. The protection device must present an acceptable capacitive
load on high-speed differential transmission lines.
Good planning and careful selection of transient voltagesuppression devices can ensure adequate circuit protection
from Electrostatic Discharge (ESD) and cable discharge events.
Designing a system for both high-speed communication and
transient immunity requirements is nontrivial. Newer Ethernet
transceivers run faster, consume less power and use less PCB
space. But these advances have contributed to a reduction of
on-chip transient-voltage protection levels. Thus, designers need
advanced system-level circuit protection to ensure Ethernet
systems remain immune to ESD and cable discharge threats.
CDE is a real and frequent phenomenon in the Ethernet
environment. Moreover, while Cable Discharge (CDE) can be
thought of as a type of Electrostatic Discharge (ESD), designers
should treat CDEs as a separate type of transient event. An
Ethernet cable -- Generally unshielded, twisted-pair Cat-5 or Cat-6
– can be simply modeled as a capacitive element that can store
a significant charge. That cable, which can run as long as 100m,
can accumulate charge via triboelectric or induction effects. Simply
dragging a cable along a carpet or removing it from a package will
lead to a stored charge. Inductive transfer from a user also can
charge a cable. Because Cat-5 and Cat-6 twisted pair cables have
low-leakage properties, the charge may remain stored on a twisted
pair for several hours and it can discharge into an Ethernet port
when a user connects it to equipment. The latter type of discharge
occurs directly into the communication interface and poses a
Protection Design Guide
particularly dangerous threat to the communication interface such
as Ethernet ports. The high peak voltage and current during a CDE
can overstress an Ethernet transceiver and lead to intermittent
malfunctions or total failure.
The semiconductor industry has recognized the need for a standard
method for testing CDE and Working Group 14, ESD Simulators,
within the Electrostatic Discharge Association (ESDA) is currently
defining a standard method for CDE testing. This work will define a
testing method that uses an ESD waveform specified in IEC 610004-2, but the new method will account for energy transfer through
a cable rather than a human body. Unlike a Human Body Model
ESD, CDE has an initial current spike followed by a characteristic
plateau and then a ringing signal with rapid polarity changes. In
many cases, cable discharges can deliver more damaging energy
to CMOS structures that can a Human Body Model ESD. Thus it is
essential for Ethernet ports to add good system-level protection
circuits. Unfortunately, some protection circuits negatively affect
signal integrity and others offer inadequate protection. We recommend
engineers consider the following characteristics when they review
Ethernet-port protection needs:
• Fast response time
• Low clamping voltage
• Low leakage current
• Low capacitance
• High energy handling capacity
• Optimal PCB layout
First, an effective Ethernet-protection device must offer a response
time faster than the transient events the system will experience.
Thus to safely attenuate a fast discharge during ESDs and CDEs, the
protection device must respond within hundreds of picoseconds,
faster than the ESD rise time. Figure 1 shows an example of a
protection circuit scheme with a sub-nanosecond response time.
Placing the protection devices “behind” the Ethernet transformer
further reduces surges.
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
35
Applications
Computer & Digital Video Protection
Second, a well devised protection circuit must provide a low
clamping voltage for a transient pulse. A transient voltage suppressor
(TVS) such as the RClamp2504N (Shown in Figure 1) diode array
offers a 4V clamping voltage (Vc) for a peak pulse current (Ipp) of
1A. Its Vc increases linearly to about 10V for an Ipp of 25A. This
type of low-voltage clamping response provides a large protection
margin for an Ethernet transceiver.
Finally, the capacitance of a protection circuit must have minimal
effect on Ethernet signal integrity. At Gigabit Ethernet speeds you can
no longer treat the interface as a lumped-element system but must
consider it as a transmission line in which the effect of capacitance
elements on signal performance becomes consequential. Excess
capacitance loading can cause signal reflections and an impedance
mismatch on the transmission line. Choosing components with
minimal line-to-line and line-to-ground capacitance can help to
ensure a small and acceptable level of signal distortion.
TPA+
TPA-
RClamp2504N
RJ-45
TPB+
TPB-
Ethernet
PHY
TPC+
TPC-
RClamp2504N
TPD+
TPD-
Figure 1 – Cable Discharge Ethernet Protection with RClamp2504N
Protection Design Guide
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
36
TVS Package Drawings
Computer & Digital Video Protection
SLP4016P16
SLP3016P12
1
2
SLP1616P6
2.10
3.00
4.00
1
SLP2116P8
1
2
1.6
2
1
1.60
1.60
1.6
1.60
6
0.50 BSC
0.50 BSC
0.58
0.58
SLP3313P16
1.70
1.70
1 2
1.30
0.40 BSC
1.30
1.30
0.40 BSC
0.40 BSC
0.40 BSC
0.50
0.50
SLP2626P10
SLP1713P8T
1 2
1 2
1.30
12
SLP1713P8
2.50
3.30
0.60
0.58
SLP2513P12
1 2
0.50 BSC
0.50 BSC
0.40
0.50
SLP2020P6
SC-89
SC-75
1.60
2.60
CL
2.00
1
CL 2.60
0.50 BSC
1.70
0.50
3
0.801.60
2.00
1.25 1.70
12
0.50 BSC
0.60
SLP1610P4
2.5
1
2
1
SLP1006P2T
1.0
1.0
0.60
0.60
0.65
0.65
Protection Design Guide
0.58
SLP1006P2
1.0
0.60
0.40 BSC
0.58
SLP1006P3T
1.0
1.0
0.50 BSC
0.58
SLP1006P3
0.50
1.2
12
1.00
0.50 BSC
0.58
SLP1210N6
1.45
1.0
0.50 BSC
0.65
0.75
SLP1510N6
1.6
2
1.0
1.000 BSC
0.60
0.60
SLP2510P8
1
0.30 BSC
0.65 BSC
0.40
0.60
0.65
0.50
©2010 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
0.40
37
Design & Application Center and Sales Office
Sales/Support Offices
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Corporate Headquarters
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©2010 Semtech Corporation. All rights reserved. | 200 Flynn Road, Camarillo, CA 93012 | www.semtech.com
Semtech International AG, the Semtech International AG logo, RailClamp, RClamp, EClamp, MicroClamp, µClamp, TransClamp and TClamp are registered marks of Semtech Corporation.
All other registered marks utilized in this document are the sole property of their respective owners. CompVdDG0810-AG
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