PortDG0411

2011
Protection Design Guide for
Portable Device Interfaces
www.semtech.com
Table of Contents
Portable Device Interfaces 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
Antenna protection (RClamp® 0531T) > 14
High speed interfaces protection (RClamp® 0544T) > 15
USB protection (RClamp® 0542T) > 16
USB with integration VBus protection (RClamp®1624T, RClamp® 3624T) > 17
SD/MicroSD protection (EClamp® 2410P) > 18
Audio port protection (EClamp® 2422N ) > 19
SIM card protection (EClamp® 2465T) > 20
LCD display and camera protection (EClamp® 250xK) > 21
Keypads and sidekeys protection (µClamp® 0501T, µClamp® 0511T) > 22
Low voltage keypads and sidekeys (µClamp® 2511T, µClamp® 3311T) > 23
Section III: Protection Applications
IEC61000-4-x Transient Immunity Standards > 25
HDMI protection > 29
LVDS protection > 30
USB protection > 31
EPD low voltage TVS > 32
TVS diode selection > 33
Unidirectional vs. bidirectional protection > 34
TVS package drawings > 35
Introduction & Background
Portable Device Interfaces Protection
The Need for Robust Circuit Protection
Le
ve
M
HB
2k
V
Cost of ESD design dependent on:
• Chip area
• Respins
• Resources
• Circuit performance
• Time-to-market
l
Today’s mobile communication integrated circuits (ICs) 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.
1k
VH
BM
Le
ve
l
ling Level
Safe Hand
ESD Association’s Recommended
Safe-Handling Level for On-Chip Protection
Protection Design Guide
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
4
Introduction & Background
Portable Device Interfaces 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
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
5
Introduction & Background
Portable Device Interfaces Protection
Threat Environment
Portable electronics interfaces are vulnerable to a variety of different transient voltage threats. These threats include Electrostatic
Discharge (ESD) and Cable Discharge Events (CDE). Interfaces that are accessible to human contact, such as USB ports, are vulnerable to
transient voltage threats from ESD and cable discharge transients. 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
ESD Discharge Levels per IEC61000-4-2
100%
90%
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
I at 30 ns
I at 60 ns
10%
t
30 ns
60 ns
tr = 0.7 to 1 ns
ESD Waveform per IEC 61000-4-2
Protection Design Guide
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
6
Introduction & Background
Portable Device Interfaces Protection
ESD Immunity: System Level vs. Device Level
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/MilStd 883. This is not the same as 2kV for the system level standard
(IEC 61000-4-2). 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 JEDEC
Standard 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.
Peak Current IEC vs JEDEC
IEC Level
(Contact
discharge)
ESD
Voltage
(kV)
JEDEC JESDA114E 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.
Protection Design Guide
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
7
Introduction & Background
Portable Device Interfaces Protection
TVS Diode Basics
Transient Voltage Suppression (TVS) Diodes
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.
Voltage
ESD Event
Zin
Transient
Enviroment
TVS
Diode
Protected
Circuit
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 application
processor. To address this need, Semtech has designed a family
of 2.5V working voltage protection devices for safeguarding next
generation application processors and baseband ICs.
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.
I (Amps)
TVS Diode Operation
Parameters for Effective Circuit Protection
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
Protection Design Guide
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
8
Introduction & Background
Portable Device Interfaces 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 2.5V TVS device. Built on the EPD platform, this device
offers a very low 2.5V working voltage. Notice that the Semtech 2.5V
TVS 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 2.5V TVS is significantly lower
than the typical 5V TVS protection device. As the sensitivity on next
generation ICs increases, selecting TVS devices with a lower clamping
voltage as illustrated in the chart can impact the difference
between safeguarding an IC or resulting in catastrophic damage.
Clamping Voltage vs Peak Pulse Current
Clamping Voltage - VC (V)
12
Typical 5V
ESD Protection
10
8
Semtech 2.5V TVS
6
4
Waveform
Parameters:
tr = 8µs
td = 20µs
2
0
0
2
4
6
8
10
12
Peak Pulse Current - IPP (A)
Clamping Performance for Semtech 2.5V TVS
Protection Design Guide
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
9
Introduction & Background
Portable Device Interfaces Protection
Layout Guidelines
PC board layout is an important part of transient immunity design.
This is especially critical in portable device 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.
The primary rule of thumb is to minimize the effects of parasitic
inductance by making the shunt paths as short as possible. All
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.
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 transient.
Protection Design Guide
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
10
Parts & Features
Portable Device Interfaces Protection
Parts & Features
ESD sensitive interfaces are found through out today’s advanced portable devices
increasing the need for high performance protection solutions. 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 portable product
devices within the Semtech protection portfolio.
Protection Design Guide
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
11
Parts & Features
Portable Device Interfaces Protection
Part Number
Lines
Vrwm
Cap I/O
to I/O
Ipp max
(8x20μs) Application
RClamp® 0531T
1
5V
0.5pF
4A
Antenna
Circuit Diagram
1.0 x 0.6 x 0.4 mm
RClamp® 0544T
4
5V
0.3pF
5A
HDMI
MicroSD
LVDS
2.0 x 1.0 x 0.4 mm
RClamp0544T
RClamp® 0542T
2
5V
0.4pF
max
5A
HDMI
LVDS
USB2.0 & 3.0
1.6 x 1.0 x 0.4 mm
RClamp0522T
VBus
RClamp® 1624T
3
1
5.5V
12V
0.4pF max
5A
5A
USB
VBUS
1
GND
DM
DP
GND
ID
1.7 x 1.0 x 0.4 mm
VBus
RClamp® 3624T
3
1
5.5V
28V
0.4pF max
6A
8A
USB
VBUS
1
GND
DM
DP
ID
GND
1.7 x 1.0 x 0.4 mm
EClamp® 2410P
6
5V
-
-
MicroSD
4.0 x 1.6 x 0.58 mm
GND
EClamp® 2422N
2
5V
100pF
-
Audio
GND
1.45 x 1.0 x 0.58 mm
Protection Design Guide
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
12
Parts & Features
Portable Device Interfaces Protection
Part Number
Lines
Vrwm
Cap I/O
to I/O
Ipp max
(8x20μs) Application
EClamp® 2465T
4
5V
10pF
-
SIM Cards
Circuit Diagram
1.7 x 1.3 x 0.4 mm
EClamp® 2504K
4
5V
15pF typ
-
LCD Display
Camera
1.7 x 1.3 x 0.5 mm
EClamp® 2506K
6
5V
15pF
-
LCD Display
Camera
2.5 x 1.3 x 0.5 mm
EClamp® 2508K
8
5V
15pF
-
LCD Display
Camera
3.3 x 1.3 x 0.5 mm
µClamp® 0501T
1
5V
10pF max
2A
Keypads
Sidekeys
Connectors
1.0 x 0.6 x 0.4 mm
µClamp® 0511T
1
5V
7pF max
2A
Keypads
Sidekeys
Connectors
1.0 x 0.6 x 0.4 mm
µClamp® 2511T
µClamp® 3311T
Protection Design Guide
1
1
2.5V
3.3V
7pF max
10pF max
5A
5A
Keypads
Sidekeys
Audio
Antenna
Keypads
Sidekeys
Audio
Antenna
1.0 x 0.6 x 0.4 mm
1.0 x 0.6 x 0.4 mm
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
13
Protection Solutions
Portable Device Interfaces 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)
Applications
•
•
•
•
GPS antennas
FM antennas
LVDS
High speed data lines
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.
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
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
14
Protection Solutions
Portable Device Interfaces 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 3.0GHz
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
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
15
Protection Solutions
Portable Device Interfaces Protection
RClamp® 0542T
ESD Protection for USB 2.0 / 3.0 and other
High Speed Interfaces
Features
•
•
•
•
•
•
5V Working Voltage
2-line protection
Capacitance: typical 0.3pF Line-to-Line
Low-clamping voltage
No insertion loss up to 3.0GHz
Small leadless package: 1.6 x 1.0 x 0.4 mm
Applications
•
•
•
•
Description
The RClamp0542T 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.
These devices are in a small leadless package (SLP1610P4T)
package and feature a lead-free, matte tin finish. They are compatible
with both lead free and SnPb assembly techniques. They are designed
for use in applications where board space is at a premium.
USB 2.0 / 3.0
HDMI 1.3 / 1.4
LVDS
DisplayPort
RClamp0542T
RClamp0542T
RClamp0542T flow through design allows for
a designers flexibility for part placement.
USB Connector
USB Controller
Vbus
D-
D-
D+
D+
RClamp0542T
Gnd
RClamp0542T USB 2.0 Protection
Protection Design Guide
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
16
Protection Solutions
Portable Device Interfaces Protection
RClamp® 1624T/RClamp® 3624T
ESD Protection for USB 2.0 with
Integrated 5V VBus Protection
Description
Features
•
•
•
•
•
•
•
•
Protects three I/O lines operating up to 5.5V
RClamp1624T protects Vbus line operating up to 12V
RClamp3624T protects Vbus line operating up to 28V
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 (1.7 x 1.0 x 0.4 mm)
Applications
•
•
USB 2.0
USB OTG
The RClamp1624T and Rclamp3624T are specifically designed
to protect one USB port. The flow through layout design of the
package enables designers greater flexibility with maximum signal
integrity. The unique design of this device features low capacitance
TVS diodes for protection of the USB data (DP, DM) and USB ID pins
operating at 5V. Loading capacitance on these lines is <1pF for
maximum signal integrity. An integrated 12V or 28V 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 5.5V.
These devices are in a 6-pin, RoHS compliant, SLP1710P4T package.
It measures 1.7 x 1.0 x 0.4 mm. The leads are spaced at a pitch of
0.4 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).
VBus
1
GND
DM
DP
Flow through design maximizes signal integrity.
Separate TVS for VBus protection ensures
isolation between power and data lines.
GND
ID
Connector
VBus
VBus
DM
DM
DP
DP
ID
ID
RClamp1624T or RClamp3624T
Protection Design Guide
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
USB Connector
17
Protection Solutions
Portable Device Interfaces Protection
EClamp® 2410P
ESD/EMI Protection for Multimedia Cards
Description
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 (2 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 45Ω 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 50kΩ pull up resistors included on the DAT3 line. These may be
configured for devices operating in SD or SPI mode.
Applications
•
•
T-Flash / MicroSD interfaces
MMC interfaces
EClamp2410P
MicroSD protection with integrated EMI/TVS
protection saving valuable PCB board space.
DAT 1 IN
Vss
1 16
DAT 1 OUT
DAT 0 IN
DAT 0 OUT
CLK IN
CLK OUT
Rup 15Ku
Rup 15Ku
V DD
Rup 50Ku
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
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
18
Protection Solutions
Portable Device Interfaces 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 −
Differential Mode Protection with Speaker Output
Protection of Single-Ended Mode Microphone
with Speaker Output
Protection Design Guide
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
19
Protection Solutions
Portable Device Interfaces Protection
EClamp® 2465T
ESD/EMI Protection for SIM Card in Portable Products
Features
•
•
•
•
•
•
5V working voltage
4-line protection and filtering
Capacitance: 10pF
Termination resistors: 100Ω & 47Ω
Low ESD clamping voltage
Very small package (1.7 x 1.3 x 0.4 mm)
Applications
•
•
•
•
Description
The EClamp2465T is a combination EMI filter and line termination
device with integrated TVS diodes for use on SIM card interfaces on
cellular phones and other portable electronics. The device consists
of three circuits that include series impedance matching resistors
for proper termination of the SIM card interface. Termination
resistor value of 100Ω is included on the Reset and Data lines and
47Ω on the CLK line. TVS diodes are also included on each line
for ESD protection in excess of ±15kV (air discharge) and ±8kV
(contact discharge) per IEC61000-4-2, level 4. An additional TVS
diode connection is included for protection of the voltage (Vcc) bus.
Smartphones
Portable electronics
MIDs
Tablet computers
Pin
Description
1
Data to Connector
2
CLK to Connector
3
Reset to Connector
4
N/C
5
Data to IC
6
CLK to IC
7
Reset to IC
8
Vcc to Connector
Ultra-small, 4-line EClamp2465T provides
superior ESD/EMI protection for today’s
advanced portable products
1
1
2
3
8
4
5
6
To IC
4
5
Protection for SIM Card Interface
Protection Design Guide
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
20
Protection Solutions
Portable Device Interfaces Protection
EClamp® 250xK
Advanced EMI Filtering and ESD protection for
portable applications
Features
•
•
•
•
•
•
•
5V working voltage
Three pole LC filter
Inductor: 17nH (Typical)
Total capacitance: 24pF (Typical)
Available in 4, 6, and 8 line protection
20dB minimum attenuation between 800MHz to 2.7GHz
Meets IEC61000-4-2 level 4
Description
The EClamp250xK family are low pass filter array’s with integrated
TVS diodes. They are designed to suppress unwanted EMI/RFI
signals and provide ESD protection in portable electronics. These
devices consist of four, six, or eight identical circuits comprised
of TVS diodes for ESD protection and a 3-pole inductor-capacitor
network for EMI/RFI filtering. A typical inductor value of 17nH and
a capacitor value of 12pF are used to achieve 20dB minimum
attenuation from 800MHz to 2.7GHz. The TVS diodes provide
effective suppression of ESD voltages in excess of ±15kV (air
discharge) and ±8kV (contact discharge) per IEC 61000-4-2, level 4.
Applications
•
•
Color LCD protection
Cell phone CCD camera lines
Three Pole LC EMI/ESD
protection for today’s
advanced LCD displays.
EClamp2504K
EClamp2506K
EClamp2508K
Display
Controller
Protection Design Guide
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
21
Protection Solutions
Portable Device Interfaces Protection
µClamp® 0501T & µClamp® 0511T
ESD Protection for keypads and sidekeys
Description
These µClamp devices are designed to protect sensitive electronics
from damage or latch-up due to ESD. It is designed to replace
multilayer varistors (MLVs) in portable applications such as cell
phones, notebook computers, and other portable electronics. It
features large cross-sectional area junctions for conducting high
transient currents. They offer desirable characteristics for board
level protection including fast response time, low operating and
clamping voltage and no device degradation. It may be used to
meet the ESD immunity requirements of IEC 61000-4-2, Level 4
(±15kV air, ±8kV contact discharge).
Features
•
•
•
•
•
•
•
5V working voltage
Single line protection
µClamp0501T Unidirectional protection
µClamp0501T Capacitance: 10pF (max)
µClamp0511T Bidirectional protection
µClamp0511T Capacitance: 7pF (max)
Excellent ESD Clamping
Applications
•
•
•
•
Keypad protection
Sidekey protecion
Portable electronics
Multimedia card interfaces
µClamp0501T
µClamp0511T
The µClamp0501T and µClamp0511T feature
advanced designs allowing for low capacitance
along with industry leading ESD clamping
Keypad
*
7
4
1
R1
0
8
5
2
R2
#
9
6
3
R3
C1
C2
C3
C4
Keypad array protection with µClamp0511T
Protection Design Guide
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
22
Protection Solutions
Portable Device Interfaces Protection
µClamp® 2511T & µClamp® 3311T
ESD protection for low voltage applications
Description
The low voltage uClamp series of TVS devices are designed to
replace multilayer varistors (MLVs) in portable applications such as
cell phones and notebook computers. They are designed to protect
sensitive semiconductor components from damage or upset due
to electrostatic discharge events. Both devices are constructed
using Semtech’s proprietary EPD process technology. The EPD
process provides a low standoff voltage with a significant reduction
in leakage current and capacitance. They feature true operating
voltages of 2.5V and 3.3V for superior protection when compared
to traditional pn junction devices.
Features
•
•
•
•
•
•
•
µClamp2511T - 2.5V working voltage
µClamp3311T - 3.3V working voltage
Single line protection
Low clamping voltage
Low leakage current: 10nA (typ)
Low capacitance: 10pF (max)
Bidirectional protection
Applications
•
•
•
Keypads and sidekeys
GPS, TV, and FM antennas
Audio
µClamp2511T and µClamp3311T
I (Amps)
True low voltage protection featuring an
industry leading clamping ESD performance
for 2.5V and 3.3V applications.
2.5V
5V
V (Volts)
Low Voltage IV Curve vs. Traditional 5V TVS
Protection Design Guide
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
23
Applications
Portable Device Interfaces 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
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
24
Applications
Portable Device Interfaces 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.
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
Indicated
Level
Voltage
Table 1 – IEC61000-4-2 Waveform Parameters
Protection Design Guide
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
25
Applications
Portable Device Interfaces 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
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.
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).
Figure 3 – IEC 61000-4-5 Voltage Impulse
Figure 4 – IEC 61000-4-5 Current Impulse
Protection Design Guide
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
26
Applications
Portable Device Interfaces Protection
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 opencircuit voltages by the source impedances. The short-circuit current
values are more useful in choosing a suppression element.
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 =42Ω
Line-GND
Zs = 42Ω
Line-Line
Zs = 2Ω
Line-GND
Zs = 12Ω
Line-Line
Zs =42Ω
Voltage
NO REQUIREMENT
Current
Voltage
Line-GDN
Zs =42Ω
(n/a)
0.5KV
Current
(n/a)
42A
0.5KV
1.0KV
12A
24A
(n/a)
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)
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
(n/a)
4.0KV
Note 1: Depends on class of local power supply system.
Table 3 – IEC61000-4-5 Severity Levels
Protection Design Guide
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
27
Applications
Portable Device Interfaces 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
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
28
Applications
Portable Device Interfaces 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, 8/20µs).
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
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
29
Applications
Portable Device Interfaces Protection
ESD Protection Solutions for LVDS
Low-voltage differential signaling (LVDS), is now used extensively
in several applications in portable applications, most notably used
in MIDDI and MIPI Interfaces. It provides an attractive solution - A
small-swing differential signal for fast data transfers at significantly
reduced power and with excellent noise immunity.
LVDS in mobile applications are used for high-speed serial
communications, replacing slower parallel interfaces. They
are ideal for implementing a variety of different applications
including next generation camera designs and high-speed display
communications.
At these higher speeds it is critical that the selected TVS protection
devices do not impact signal integrity and at the same time offer
ESD protection for next generation IC’s.
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
which simplifies PCB layout and improves signal integrity.
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
LVDS
Transceiver
RClamp0544T
RClamp0544T
Protection for LVDS Interface
Protection Design Guide
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
30
Applications
Portable Device Interfaces 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:
• Protects 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 are
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
RClamp1624T & RClamp3624T:
• 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
• Available in two different Vbus voltages; RClamp1624T
protects the Vbus to 12V Vrwm and the RClamp3624T protects
the Vbus to 28V Vrwm
• 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
RClamp0542T
USB Controller
Connector
Vbus
D-
D-
D+
D+
Gnd
Protection for USB 2.0 Interface
Protection Design Guide
RClamp1624T/RClamp3624T
VBus
VBus
DM
DM
DP
DP
ID
ID
USB 2.0 Protection with Vbus and ID Pin Protection
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
31
Applications
Portable Device Interfaces Protection
Semtech Low Voltage TVS
Low Voltage TVS
Conventional TVS diodes are silicon avalanche, p-n junction
devices designed to operate at voltages as low as 5 volts. They
are specifically designed with large junction areas for handling high
transient currents. However, many of today’s semiconductor devices
operate at voltages below 3.3 volts, and thus require lower voltage
protection devices. Unfortunately, for operating voltages below 5 volts,
conventional TVS diodes technology becomes impractical. This is due
to the adverse effects of high leakage current and high capacitance
caused by the high impurity concentrations that are needed to
lower the device voltage below 5 volts. Semtech’s proprietary low
voltage EPD device technology was developed to provide protection
for today’s circuits operating at voltages as low as 2.5 volts. Unlike
TVS diodes with a conventional p-n junction structure, the EPD
device utilizes a more complex four layer (n-p-p-n) structure. The
construction of these devices results in very low operating and
clamping voltage without the adverse effects mentioned above.
•
•
•
•
Working Voltage (VRWM): Maximum rated operating voltage
at which the device will appear as a high impedance to the
protected circuit
Punch-Through Voltage (VPT): Minimum rated voltage at which
the device will become a low impedance (i.e. Minimum Turn-on
Voltage). When VPT is exceeded, the device will conduct.
Snap-Back Voltage (VSB): Minimum rated voltage when the
device is in conducting state measured at Isb=50mA. This
voltage is less than the working voltage. The voltage must full
below Vsb for the device to turn off.
Clamping Voltage (VC): Maximum voltage drop across the
device at a defined peak pulse current (IPP). This is the voltage
seen by the protected circuit during a transient event.
Device Operation
Since the EPD TVS devices use a 4-layer structure, they exhibit
a slightly different IV characteristic curve when compared to
conventional devices. Figure 1 compares the IV characteristics curves
of a low voltage TVS with a working voltage (VRWM) of 3.3 volts to
the conventional device with a working voltage of 5 volts. During
normal operation, each device represents a high-impedance to
the circuit up to its working voltage. During an ESD event, they
begin to conduct and will enter a low impedance state. For the 3.3
volt device, this happens when the punch-through voltage (VPT) is
exceeded. Unlike a conventional 5 volt device, the low voltage TVS
will exhibit a slight negative resistance characteristic as it conducts
current. This characteristic aids in lowering the clamping voltage of
the device, but must be considered in applications where DC voltages
are present. The reason is the device can latch up if the DC bias
voltage is present. To better understand why, consider the IV curve
for a 3.3 volt device shown in Figure 2. During and ESD event the
device will conduct along the curve until the transient subsides.
In order for the device to turn off, the voltage must fall below the
snap-back voltage (VSB). The value is normally a minimum of 2.8
volts for a 3.3 volt device. If the device is biased at 3.3 volts, it will
never fall below the snap-back voltage and will therefore stay in a
conducting state. The amount of the current the device will sink
depends upon the bias voltage and the DC supply capability. If the
amount of current that is conducted exceeds the device steady
state capability, the TVS device can become damaged or destroyed.
Figure 1 - 3.3V vs. 5V TVS IV Curve
Figure 2 - 3.3V TVS IV Characteristic Curve
Protection Design Guide
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
32
Applications
Portable Device Interfaces Protection
TVS Diode Selection
Selection of a suitable component will depend on the number of
lines to be protected, the available board space, and the electrical
characteristics of the circuit to be protected. TVS diodes are
available in a variety of packages and configurations suitable for
use in today’s advanced electronic systems.
Selection Guidelines
TVS diode selection involves comparison of device parameters
with circuit conditions. The following selection guidelines are
recommended:
•
No matter what the applications is, however, certain device
parameters and guidelines form the basis for device selection.
•
TVS Diode Terminology
•
•
•
•
•
•
•
A typical IV characteristic curve for a bidirectional TVS diode is
shown in Figure 1. The key device parameters
Reverse Standoff Voltage (VRWM): This is the normal DC
operating voltage of the device. At this point, the device will
appear as a high impedance to the protected circuit. Discrete
devices are available with standoff voltages ranging from 2.5V
to 70V. This parameter is also referred to as working voltage.
Reverse Breakdown Voltage (VBR): This is the point where the
device begins to conduct in avalanche mode and becomes a
low impedance path for the transient. Breakdown voltage is
measured at a test current (IT), typically 1mA or 10mA.
Peak Pulse Current (IPP): Maximum permissible surge current
which the device can withstand without damage. TVS diode
data sheets specify a peak pulse capability for a particular
transient waveform. Most TVS diodes are rated using a
8/20µs or 10/1000µs impulse waveform.
TVS diodes can withstand higher peak pulse current for
shorter duration pulses.
Clamping Voltage (VC): Maximum voltage drop across the TVS
for a particular peak pulse current.
•
Select a device with a reverse standoff voltage greater than or
equal to the normal operating voltage of the circuit.
Select a device which is capable of dissipating the expected
transcient peak pulse current.
The device clamping voltage should be less than the maximum
voltage handling capability of the protected circuit for the
same pulse waveforms.
For systems using high speed data rates, device junction
capacitance will have to be considered. Semtech
manufactures special low capacitance devices for those
applications.
There may be applications where the actual transient current
cannot be defined. Often, the designer will have to meet the
requirements of certain transient immunity specifications. At the
very least, identification of the source of the threat is necessary;
lightning, inductive switching, ESD, etc.
Device
Parameter
Circuit Conditions
VRWM
≥
Normal circuit operating voltage
IPP
≥
Expected transient current
VC
≤
Maximum allowable voltage across the
protected component
CJ
<
Maximum loading capacitance for
signal integrity
Figure 2 - Selection Summary
Figure 1 - Bidirectional IV Characteristic Curve
Protection Design Guide
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
33
Applications
Portable Device Interfaces Protection
Unidirectional and Bidirectional Protection
Unidirectional Protection
Bidirectional Protection
Figure 1 illustrates a large transient at the input of a circuit
protected by a unidirectional TVS diode. During the positive
spike, the TVS diode junction is reversed biased. The device acts
in avalanche mode as the transient current i1 flows. The spike
is clamped at or below the maximum clamping voltage of the
protection device. During the negative spike, the TVS diode junction
is foward biased. The negative spike is clamped to one diode drop
as the device conducts i2 in the foward direction.
Figure 2 illustrates a large transient at the input circuit protected by
a bidirectional TVS diode. The positive and negative spikes are both
clamped at or below the maximum clamping voltage of the device.
During the positive spike, D1 conducts in the forward direction (i3)
and D2 is reversed biased conducting in avalanche mode. During
the negative spike, D2 conducts in the forwards direction (i4) and
D1 is reversd biased conducting in the avalanche mode.
VIN
VOUT
VOUT
i3
i3
i4
Figure 1 - Unidirectional Device
(Asymmectric Clamping)
Protection Design Guide
VIN
i4
Figure 2 - Bidirectional Device
(Symmectrical Clamping)
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
34
TVS Package Drawings
Portable Device Interfaces 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
SC-89
2.00
0.50 BSC
1.70
1.25 1.70
SLP1610P4
2.5
1
2
0.40
SLP1510N6
1.6
2
1
0.58
1.2
12
1.00
0.58
SLP1006P3
0.58
SLP1006P2
SLP1006P2T
1.0
1.0
1.0
0.60
0.60
0.60
0.40 BSC
0.58
SLP1006P3T
1.0
1.0
0.50 BSC
0.50 BSC
0.50 BSC
SLP1210N6
1.45
1.0
1.0
1.0 BSC
0.60
0.60
SLP2510P8
1.0
0.30 BSC
0.65 BSC
0.60
0.65
0.65
Protection Design Guide
0.40 BSC
0.50
1
CL 2.60
0.50
SLP1710P4T
1.70
2.00
1
0.40
0.50
SLP2020P6
2.60
CL
0.65
0.40 BSC
0.40 BSC
0.50
SLP2626P10
1.30
1.30
0.40 BSC
0.50
1
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
0.60
0.65
0.50
©2011 Copyright Semtech Corporation. All rights reserved. All Clamp products are registered trademarks of Semtech Corporation.
0.40
35
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©2011 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. PortDG0411-AG