Application Notes

AN10495
HDMI, DVI interface protection
Rev. 01 — 18 December 2007
Application note
Document information
Info
Content
Keywords
DVI, HDMI, DDC, CEC, Hot-Plug, level shifting, ESD, backdrive protection
Abstract
This application note gives an overview about the importance and various
opportunities for sophisticated ESD protection for HDMI receiver and
transmitter interfaces. A broad portfolio of interface solutions starting from
pure ESD protection arrays up to fully integrated interface ICs including
level shifting, ESD and backdrive protection are discussed. Important TDR
measurements as well as Eye diagrams demonstrate the high
performance of these NXP Semiconductors products with the world-wide
lowest line capacitance available in Silicon technology. It is demonstrated,
that such fully integrated solutions from NXP Semiconductors enables
easy routing and relaxed board design. The presented solutions are fully
compliant with HDMI 1.2 and HDMI 1.3.
AN10495
NXP Semiconductors
HDMI, DVI interface protection
Revision history
Rev
Date
Description
01
20071218
Initial version
Contact information
For additional information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: [email protected]
AN10495_1
Application note
© NXP B.V. 2007. All rights reserved.
Rev. 01 — 18 December 2007
2 of 32
AN10495
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HDMI, DVI interface protection
1. Introduction
The High Definition Multimedia Interface (HDMI) is the state-of-the-art interface combining
the video and audio signals into a single digital interface for use with Digital Versatile Disc
(DVD) players, Digital TeleVisions (DTVs), Set-Top Boxes (STBs), game consoles and
other audiovisual devices.
HDMI is a merge of:
• DVI for the TMDS interface (mainly single link)
• IEC 60958 and IEC 61937 for the audio
• EIA/CEA-861B for video timing and auxiliary information
HDMI supports standard, enhanced or high-definition video signals plus standard to
multi-channel surround-sound audio, and HDCP copy protection. It ensures that the HDMI
source is using video and audio formats (such as EDID) which are supported by the HDMI
sink. HDMI includes uncompressed digital video, a high bandwidth in the
gigabytes-per-second range, one connector instead of several cables and connectors,
and communication between the video source and the receiver e.g. a TV set.
The HDMI Founders group includes the leading consumer electronics manufacturers
Hitachi, Matsushita Electric Industrial, Philips, Sony, Thomson, Toshiba, and Silicon
Image. Digital Content Protection, LLC (a subsidiary of Intel) is providing High-bandwidth
Digital Content Protection (HDCP) for HDMI. In addition, HDMI has the support of major
motion picture producers Fox, Universal, Warner Bros. and Disney, and system operators
DirecTV, EchoStar as well as CableLabs.
The HDMI Founders group has established Authorized Testing Centers (ATC) where
licensed manufacturers can submit their products for HDMI compliance testing. Currently,
ATCs are located at Matsushita Electric Industrial in Japan, NXP Semiconductors in
France (Caen), and Silicon Image in USA.
Both HDMI receiver and HDMI transceiver ICs are manufactured in processes with deep
sub-micron feature sizes. These sensitive sub-micron CMOS processes typically provide
a limited 2 kV ESD protection according to the Human Body Model (HBM, MIL-883E
method 3015.7/JESD22-A114-D) standard in order to provide protection during the
manufacturing and assembly process. An end-user application such as a TV or Set Top
Box (STB) encounters a high risk of ESD damage, which is specifically high for Hot-Plug
interfaces such as HDMI. In these Hot-Plug interfaces, the consumer can plug or unplug
cables while the application is running. Furthermore, most manufacturers seek to get
certain consumer electronics certificates (e.g. CE norm), which do require high-level ESD
protection according to the IEC 61000-4-2 standard.
In the above cases, all manufacturers strongly recommend applying ESD protection
circuitry at their external port interface. NXP Semiconductors has developed a broad
range of DVI/HDMI interface ICs which not only provide high-level ESD protection, but
also incorporate level shifting for the DDC signals and provide backdrive protection
functionality. Such ICs are essential for a high-speed DVI/HDMI port with data rates in the
GHz range.
For ESD protection, NXP Semiconductors offers a broad variety of solutions such as a
4-channel pure ESD protection solution device (IP4280CZ10) as well as a fully integrated
interface IC including ESD protection, level shifting and backdrive protection device
AN10495_1
Application note
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Rev. 01 — 18 December 2007
3 of 32
AN10495
NXP Semiconductors
HDMI, DVI interface protection
(IP4776CZ38). Depending on the specific HDMI transmitter and the customer choice, any
of these solutions can be applied. Based on current experience, NXP Semiconductors
recommends the higher integrated solutions in order to obtain easier routing, relaxed
board layout, smallest footprints and highest ESD protection level.
This report is structured as follows.
Section 2 gives an overview and a short description of the relevant ESD protection
standards. A special rail-to-rail-based diode concept, as used by NXP Semiconductors to
achieve ultra-low line capacitance for high-speed data interface, is discussed in Section 3.
Section 4 gives a brief explanation of level shifting and Section 5 discusses backdrive
protection required at some HDMI ports. In Section 6 an application for ESD protection
without level shifting is drawn. Some basic information about Printed-Circuit Board (PCB)
design is documented in Section 7. Section 8 introduces various ESD protection solutions
for DVI/HDMI ports, starting from pure protection functionality up to a fully integrated
interface IC. This section also includes all relevant HDMI compliance tests such as TDR
(Time Domain Reflection) or Eye patterns proving the high performance of the NXP
Semiconductors high-speed ESD protection devices. Section 9 ends this application note
with a brief summary.
2. ESD protection standards
2.1 IEC 61000-4-2
Interfaces of consumer electronic equipment are widely specified according to the
International Electrotechnical Commission standard IEC 61000-4-2. This standard is not
targeted towards particular devices but towards general equipment, systems and
subsystems that may be involved in electrostatic discharge. The model, shown in
Figure 1, consists of a 150 pF capacitor and a 330 Ω series resistor representing the
counterpart to the Device Under Test (DUT).
330 Ω
50 MΩ to 100 MΩ
V
high-voltage
generator
DUT
150 pF
001aaf202
Fig 1. Test circuit according IEC 61000-4-2
According to this standard, the ESD surge can be applied by contact as well as by air
discharge and is classified by the capacitor’s charge voltage shown in Table 1.
For consumer products, class 4 is regarded as being the most appropriate level to achieve
a reasonable relation between cost and prevention of field returns due to ESD failures.
AN10495_1
Application note
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Rev. 01 — 18 December 2007
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HDMI, DVI interface protection
Table 1.
IEC 61000-4-2 ESD surge classification[1]
Contact discharge
Air discharge
Class
Test voltage (kV) Maximum current (A) Class
Test voltage (kV)
1
2
7.5
1
2
2
4
15
2
4
3
6
22.5
3
8
4
8
30
4
15
X
special
special
X
special
[1]
X is an open level that must be specified in the dedicated device specification. If higher voltages than level
4 are specified, special test equipment may be needed.
A typical ESD current pulse form generated by an ESD surge according to IEC 61000-4-2
shown in Figure 2.
001aaa631
IPP
100 %
90 %
10 %
tr = 0.7 ns to 1 ns
t
30 ns
60 ns
Fig 2. ESD surge according IEC 61000-4-2
A characteristic of IEC 61000-4-2 ESD pulses is the very short rising edge; the maximum
peak current is reached within 0.7 ns to 1 ns. This requires a very short reaction time of
the ESD protection circuit to avoid severe voltage overshoots at the protected device.
Therefore, it is important to put special attention to the selection of the correct diodes.
Ultra-low line capacitance diodes are the recommended device of choice, especially for
high-speed interfaces such as HDMI, as they react very fast (in the nano second range).
Another issue besides the voltage clamping is the maximum current injected into a device
during an ESD discharge. To withstand a maximum possible current of 30 A as specified
in IEC 61000-4-2, level 4, careful dimensioning of all conductors and components affected
by an ESD surge is mandatory. Using appropriate structural dimensions helps to obtain
very short reaction times of the ESD protection circuits avoiding permanent damage
caused by for example, electro-migration of aluminum tracks.
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HDMI, DVI interface protection
2.2 Human Body Model (HBM, MIL-883E method 3015.7)
The HBM standard simulates an ESD surge generated by human contact to electronic
components.
10 MΩ to 100 MΩ
V
high-voltage
generator
1.5 kΩ
DUT
100 pF
001aaf203
Fig 3. Test circuit according to MIL-883E method 3015.7
As shown in Figure 3, the model consists of a 100 pF capacitor and a 1.5 kΩ serial
resistor to simulate a human body. According to the standard, the ESD surge is applied by
contact and the test is applied in both the positive and negative direction. Three different
classes differentiated by the capacitor’s charge voltage are shown in Table 2.
Table 2.
MIL-883E method 3015.7 ESD surge classification, contact discharge
Class
Test voltage (V)
Maximum current (A)
1
0 to 1999
1.33
2
2000 to 3999
2.67
3
4000 and above
> 2.67
A typical ESD current pulse form generated by an ESD surge according to MIL-883E
method 3015.7 is shown in Figure 4.
IPP
Ir < 15 % of IPP
100 %
90 %
Ir peak-peak not
drawn to scale
36.8 %
10 %
t
tr ≤ 10 ns
150 ns ± 20 ns
001aaf204
Fig 4. ESD surge according to MIL-883E method 3015.7
The shape of the ESD surge looks similar to an RC-charge/-discharge curve. As the
maximum current applied is in the order of magnitude of a few amperes only, and the rise
time is a few nanoseconds, the reaction time of an ESD protection circuit is relatively not
critical.
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HDMI, DVI interface protection
2.3 Comparison of IEC and MIL standard
Direct comparison of both ESD models is difficult due to the differences in the discharge
waveforms. Generally, the maximum injected current and the total load of the IEC 610004-2 standard is much higher than the one specified in the Human Body Model (HBM)
according to the MIL-883E method 3015.7.
The rise time of the current waveform is different due to the series resistor being 1.5 kΩ in
the HBM instead of 330 Ω as in the IEC 61000 model.
While the rise time for the IEC-compliant current waveform is specified as being 0.7 ns to
1 ns, the HBM waveform is specified as having a rise time below 10 ns only.
Assuming that the maximum current rating is more stressful to a protection ESD diode
and other affected components than the duration of the current flow, the IEC 61000-4-2
standard is the more stringent of the two tests to withstand.
∂Q
As the surge current is determined by the gradient of charge over time I = ------- , the
∂t
∂Q
voltage drop across the protection diode can be described as being V ≈ R intrinsic × ------- ,
∂t
where Rintrinsic is the inner resistance of the diode.
Looking at the likelihood of voltage overshoots being attributable to the rise time of ESD
surges, one can easily derive, that shorter rise times will lead to higher voltage overshoots
due to the reaction time of the respective protection devices. Even if, for instance, the test
voltage of both methods is similar, the IEC standard is the more stringent test for a
protection circuit to withstand because the maximum internal voltage will reach a higher
level during a discharge.
In the case of the higher resistor value in the HBM, the maximum current would be in the
order of some amperes only. In comparison to this, the maximum current of an ESD surge
according to IEC can reach as high as 30 A.
While integrated components such as resistors and also integrated planar aluminum
metal wires have a limited maximum current density to avoid degradation effects such as,
for example, electro-migration, certain design rules have to be maintained. High current
densities might also result in a too high thermal stress in resistors and lead to a
permanent shift of resistance value.
Both topics, electro-migration and thermal stress, are taken into account during our
standard design procedure to avoid failure during a nearly unlimited number of ESD
surges below the maximum voltage limit specified.
AN10495_1
Application note
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Rev. 01 — 18 December 2007
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HDMI, DVI interface protection
3. Rail-to-rail concept
With the rail-to-rail concept, a negative ESD strike on the I/O pin will cause one rail-to-rail
diode (the lower diode at the flash sign in Figure 5a) to become forward biased, thereby
transferring the ESD strike through the lower diode to ground.
A positive discharge strike will cause the other rail-to-rail diode (the upper diode at the
flash sign in Figure 5b) to become forward biased transferring the discharge to the VCC pin
of the device. To prevent charging of the supply, the additional Zener diode between
ground and VCC will clamp voltages exceeding the Zener clamping voltage caused by the
ESD strike to ground.
TMDS_D0+
TMDS_CLK+
TMDS_D0+
TMDS_BIAS
TMDS_CLK+
TMDS_BIAS
VCC(5V0)
VCC(5V0)
−
TMDS_GND
TMDS_D0−
+
TMDS_GND
TMDS_CLK−
TMDS_D0−
001aaf206
a. Negative ESD strike
TMDS_CLK−
001aaf205
b. Positive ESD strike
Fig 5. Rail-to-rail diode concept as used by NXP Semiconductors achieves ultra-low line
capacitance
4. Level shifting
The new generation CMOS devices cannot handle high supply voltages which are
specified in the DVI and HDMI specification. The typical core voltage of such a DVI/HDMI
device is 1.8 V and the I/O cells are 3.3 V tolerant (GPIO, I2C-bus). The IP4776CZ38
provides a 3.3 V to 5.0 V bidirectional level shifting between the DVI/HDMI
transmitter/receiver chip and the HDMI plug. The implemented level shifter can also
handle lower voltages like 3.3 V to support HDMI devices which are less tolerant.
In addition to the level shifting functionality as shown in Figure 6, an external pull-up
resistor is needed to enable level shifting.
VCC(3V3) TMDS_BIAS
3.3 V
5V
001aaf207
Fig 6. Principles of I2C-bus level shifter
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HDMI, DVI interface protection
The NMOS FET, used in the level shifter is connected at the gate to the lower supply
voltage (3.3 V).
+5 V
Vgate
100 kΩ
Vout
V
001aag010
Fig 7. Measurements of I2C-bus level shifter
The output voltage at the low voltage side is Vgate(3.3V) − Vth. To reach the full 3.3 V high
level voltage an additional pull-up resistor is needed. For signals like Hot-Plug the output
voltage is high enough (about 2.4 V) to reach the logic level (2.0 V) and an additional
pull-up resistor is not necessary.
The differential voltage between the gate and the low-level output is not constant. The
voltage difference is increasing with the gate voltage as shown in Figure 8.
001aag011
3.5
voltage
(V)
2.5
Vdrain/source
1.5
Vgate − Vdrain/source
0.5
−0.5
0
1
2
3
4
5
Vgate (V)
Fig 8. Output difference voltage at level shifter
The line Vdrain/source shows the output voltage at the low-level side (3.3 V). A minimum
gate voltage Vgate is needed to produce an output voltage. The line Vgate − Vdrain/source
shows the difference between the gate voltage and the output voltage.
If the supply voltage Vgate is 0 V, e.g. at power-down, the FET is high ohmic and therefore
disconnects the input from the output. This is the mentioned backdrive protection that
ensures that a switched-off device like a TV set is not pulling down any CEC, DDC or
Hot-Plug signal.
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HDMI, DVI interface protection
4.1 DDC bus level shifting
The HDMI specification requires a pull-down resistor Rp of 1.5 kΩ to 2.2 kΩ for an HDMI
source, 47 kΩ for an HDMI sink and a voltage of 5 V. The load of a cable (Ccable) is
specified with a maximum value of 700 pF. The capacitive load of the HDMI sink and
source is specified as 50 pF. The new CMOS technologies support lower voltages and
today the maximum voltage at a pin is 3.3 V or less. Such a device requires a level shift
function.
HDMI source
HDMI sink
TMDS_BIAS
+3.3 V
TMDS_BIAS
+5.0 V
+5.0 V
Rp
1.5 kΩ
Rp
47 kΩ
+3.3 V
Rp
Rp
47 kΩ
47 kΩ
DDC clock, data
DDC clock, data
IP4776CZ38
IP4776CZ38
Ccable
001aag012
Fig 9. DDC application with level shift to 3.3 V and ESD protection
For devices without any need for level shifting, the level shifting function can be disabled
by shorting the input and output pins of the device. The ESD protection continues to
operate.
HDMI source
HDMI sink
TMDS_BIAS
+3.3 V
TMDS_BIAS
+5.0 V
+5.0 V
Rp
1.5 kΩ
+3.3 V
Rp
47 kΩ
DDC clock, data
DDC clock, data
IP4776CZ38
Ccable
IP4776CZ38
001aag013
Fig 10. DDC application with ESD protection
The short can also be realized by a 0 Ω (zero Ohm) resistor on the PCB. This short also
disables the backdrive protection. To keep the timing on the DDC lines synchronous we
recommend using a 47 kΩ resistor for the DDC clock and the DDC data at the HDMI sink
(start, stop condition detecting).
4.2 CEC bus
The single line CEC bus is working with a maximum signal voltage of 3.63 V at 1 kHz
clock speed. Still the level shifting function in combination with backdrive protection can be
used to adapt and protect the signal to a low-voltage DVI or HDMI input pin of a
transmitter or receiver device.
AN10495_1
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Rev. 01 — 18 December 2007
10 of 32
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HDMI, DVI interface protection
HDMI source
HDMI sink
TMDS_BIAS
low
voltage
TMDS_BIAS
+3.3 V
Rp
27 kΩ
Rp
47 kΩ
low
voltage
+3.3 V
Rp
Rp
47 kΩ
27 kΩ
CEC
CEC
IP4776CZ38
IP4776CZ38
Ccable
001aag014
Fig 11. CEC application with level shift to low voltage and ESD protection
If backdrive protection and level shift function are not required, they can be disabled by
shorting the input and output pins of the device so that only the ESD protection is used.
HDMI source
HDMI sink
TMDS_BIAS
TMDS_BIAS
+3.3 V
+3.3 V
Rp
27 kΩ
Rp
27 kΩ
CEC
CEC
IP4776CZ38
IP4776CZ38
Ccable
001aag015
Fig 12. CEC application with ESD protection
4.3 Hot-Plug application
The Hot-Plug signal is used to control the communication between an HDMI sink and an
HDMI source. The HDMI sink, for example a TV set, can pull down the Hot-Plug signal to
a logic 0 as long as the sink is not ready for operation e.g. at system start-up.
HDMI source
HDMI
connector
HDMI sink
HDMI
connector
18
18
19
19
5V
1 kΩ
2.4 V to 5.3 V
001aag019
Fig 13. Principles of the Hot-Plug signal
The HDMI source uses a 2 V level to detect the Hot-Plug signal. The 5 V of the HDMI
source or an internal voltage is used to generate the Hot-Plug signal via a 1 kΩ resistor
(Ri).
AN10495_1
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Rev. 01 — 18 December 2007
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HDMI, DVI interface protection
HDMI source
HDMI connector
pin 18
HDMI sink
HDMI connector
pin 18
5V
TMDS_BIAS
TMDS_BIAS
+3.3 V
+3.3 V
Rp
50 kΩ
HDMI connector
pin 19
HDMI connector
pin 19
5V
Ri
R
1 kΩ
100 kΩ
Hot-Plug
GPIO
Hot-Plug
IP4776CZ38
Rp
IP4776CZ38
15 kΩ
001aag016
Fig 14. Hot-Plug, level shift and backdrive protection
The Rp of 50 kΩ can be removed because 2.4 V will be reached at the Hot-Plug out if the
gate of the transistor is connected to 3.3 V. The combination of the pull-up resistors of
50 kΩ and 15 kΩ has the disadvantage that the low level (0.76 V) is close to the limit
(0.8 V).
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HDMI, DVI interface protection
5. Backdrive protection
External signals can cause backdrive problems, particularly on output signals with
pull-ups at the other end of the cable. I2C-bus signals like DDC clock, DDC data and the
CEC lines can cause a potential problem on the DVI/HDMI source and sink side.
Advanced sub-micron CMOS technology-based ICs, such as DVI/HDMI transceivers, are
designed to have a typical internal 2 kV HBM ESD protection, intended to allow safe IC
handling during the manufacturing process. These internal ESD diodes can create a
direct path to ground so that pull-ups on the other end of the cable will sink current into the
local, switched-off, TMDS_BIAS rail. Severe damage can be caused to unprotected
sub-micron CMOS HDMI receiver and/or transmitter ICs, if for instance a non-standard
DVI/HDMI adapter is used or two sinks/sources driving a DVI/HDMI source are plugged
into each other. These configurations possibly might cause actual damage to the
unprotected design. An external interface protection and isolation device, like the
IP4776CZ38, will usually consume most of the energy and so protect the much more
sensitive DVI/HDMI IC. To prevent these situations, the IP4776CZ38 contains an
integrated backdrive protection that guarantees a maximum current of 5 µA on any I/O pin
if the I/O pin voltage is higher than the supply voltage of the IP4776CZ38.
supply off
5V
HDMI source
HDMI sink
backdrive
current
I2C-BUS ASIC
HDMI ASIC
001aaf208
Fig 15. Principles of backdrive protection
Figure 15 shows the path of the current when the HDMI source is switched off and the
HDMI sink is still active. The ESD diodes of the HDMI source device can create a short for
signals at the HDMI cable.
HDMI source
HDMI sink
TMDS_BIAS
TMDS_BIAS
+5.0 V
supply off
Rp
1.5 kΩ
Rp
47 kΩ
+3.3 V
Rp
Rp
47 kΩ
47 kΩ
DDC clock, data
DDC clock, data
IP4776CZ38
Ccable
IP4776CZ38
001aag017
Fig 16. Backdrive protection at DDC bus
The level shift FET is high ohmic at power-down, preventing any backdrive current.
AN10495_1
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Rev. 01 — 18 December 2007
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HDMI, DVI interface protection
6. ESD protection of HDMI transceivers not requiring level shifting
Depending on the application, level shifting and/or backdrive protection might not be
necessary for the DVI/HDMI interface. NXP Semiconductors provide a solution that offer
the required high ESD protection (IEC 61000-4-2 level 4) combined with an ultra-low line
capacitance.
Appropriate ESD protection using only a single chip is offered by the new generation
ultra-low line capacitance diodes of the IP4280CZ10. This device is characterized by a
line capacitance of only 0.7 pF, providing excellent protection, lowest capacitive load to the
system and optimized parallel routing.
pin 1
TMDS_CH1+
pin 3
VCC
pin 4
TMDS_CH2+
10 n.c.
TMDS_CH1+
1
n.c.
2
VCC
3
TMDS_CH2+
4
7
n.c.
n.c.
5
6
TMDS_CH2−
IP4280CZ10
9
TMDS_CH1−
8
GND
pin 6
TMDS_CH2−
pin 9
TMDS_CH1−
pin 8
GND
001aag076
a. Pin allocation
001aag020
b. Ultra-low line capacitance diodes
Fig 17. IP4280CZ10
Using the IP4776CZ38 including the level shifting feature but in a configuration in which
level shifting is deactivated (by 5 V to the VCC(3V3) pin), the backdrive protection and the
ESD protection are supported for DDC, CEC and Hot-Plug.
HDMI source
HDMI sink
TMDS_BIAS
TMDS_BIAS
+5.0 V
+5.0 V
Rp
1.5 kΩ
Rp
47 kΩ
Rp
Rp
47 kΩ
47 kΩ
DDC clock, data
DDC clock, data
IP4776CZ38
Ccable
IP4776CZ38
001aag018
Fig 18. IP4776CZ38 with ESD and backdrive protection
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Rev. 01 — 18 December 2007
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7. PCB design
D2+
D1+
3
5V 3V
C C
C
C
V V GND
D1−
CLK−
CLK+
D0−
4-layer PCB
standard FR4 material
TMDS_VDD
8 CB
Z3 P
C n
7B tio
47 ica
IP pl
Ap
ug
pl ta
ot a
H C_dlk
D c
D C_
D in
D C_
E
C
D0+
NXP
Integrated
Discretes
IDs_boar d20_rev4
IDs 11/05
D2−
The design of the TMDS lines with respect to the impedance required by the HDMI
specification (85 Ω to 115 Ω) requires detailed knowledge of the PCB materials used and
the geometrical design of the Micro Strip Lines (MSL).
001aag021
Fig 19. Reference board IP4776CZ38
The most effective way to design the TMDS lines is by using a field simulator. Based on
the simulation results, a test PCB should be designed to compare the simulation results
with a real PCB. The simulation can be optimized by using the parameters of the PCB
material, which will differ from one PCB vendor to another. If a field simulator is not
available, one test PCB can be made with different geometrical test structures to find the
optimal design for this specific PCB material.
The NXP PCB recommendation was verified in the lab and in the HDMI compliance center
at Caen (France) but be aware that the PCB material may differ from yours.
Experience shows that the PCB material has a major impact on the impedance of the
micro strip lines. To evaluate the PCB material used and the number of layers, a test PCB
can be made as shown in Figure 20.
AN10495_1
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Rev. 01 — 18 December 2007
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NXP Semiconductors
HDMI, DVI interface protection
HDMI
connector
85 Ω
90 Ω
95 Ω
100 Ω
HDMI
connector
100 Ω
105 Ω
110 Ω
115 Ω
HDMI
connector
HDMI
connector
IP4776CZ38
85 Ω
90 Ω
95 Ω
100 Ω
IP4776CZ38
100 Ω
105 Ω
110 Ω
115 Ω
HDMI
connector
IP4776CZ38
100 Ω
100 Ω
100 Ω
100 Ω
001aag022
Fig 20. Test structure PCB (principles)
The first two structures without an IP4776CZ38 are used to verify the impedance of the
micro strip lines. The next two structures will indicate what the impedance underneath the
IP4776CZ38 has to look like in order to pass the HDMI compliance test. The last structure
gives a good indication about the spread of the impedance and the device position.
Section 7.1 gives a principle description: the exact dimensions and positions are available
as a Gerber file. The Gerber file of the test PCB will be made available upon request.
The impedance measurements need special equipment. For customers who do not have
such equipment or require a second analysis result, we offer a TDR analysis of the PCB to
ensure a pass at the HDMI-compliance test.
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7.1 Geometry of micro strip lines (TMDS)
The design of a 100 Ω differential impedance has to be optimized for the PCB material
and the number of layers. It is possible to calculate the impedance (Z0) and the differential
impedance (Zdiff) using the following equations (see also Figure 21).


60
4h
 Z 0 = --------------------------------------- × ln  -------------------------------------  Ω
0.67 ( 0.8W + t ) 
0.457ε r + 0.67

 – 0.96 ---


h 
≈ 2Z 0  1 – 0.48e
 Ω


S
Z diff
The results are valid up to a few GHz.
W
S
W
t
h
εr
ground plane
001aag023
Fig 21. Geometrics for TMDS lines
Solid ground plane underneath the micro strip lines is part of the micro strip line design.
Table 3.
Parameters for 2- and 4-layer PCB (FR4)
Parameter
4 layer
2 layer
Unit
Trace width (W)
5 (0.127)
8 (0.203)
mil (mm)
Spacing (S)
4 (0.102)
4 (0.102)
mil (mm)
mil (mm)
Layer height (h)
4.5 (0.114)
63 (1.6)
Relative permittivity (εr)
4.3
4.3
Copper thickness (t)
1 (0.0254)
1 (0.0254)
mil (mm)
Zdiff
100.37
108.22
Ω
As an example, Table 3 shows all parameters which are necessary to design a 2-layer and
a 4-layer board for a differential impedance (Zdiff) of 100 Ω.
Demonstration versions of simple simulator software are available on the internet to make
the first steps.
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7.2 TDR measurements of the IP4280CZ10
Prior to mass production of any licensed product or component that claims compliance
with the HDMI specification, each adopter must test a representative sample for HDMI
compliance. First, the adopter must self-test as specified in the HDMI compliance test
specification. The HDMI compliance test specification provides a set of testing procedures
and establishes certain minimum requirements. Such compliance testing is limited to
evaluating the compliance of the application with the HDMI specification.
The compliance test specification was developed by the HDMI founders group to assist
manufacturers in ensuring the compliance of their products with the HDMI specification. It
consists of numerous tests designed to check for compatibility of various HDMI-related
aspects of a product, including audio, video, EDID, electrical signaling, protocols, etc.
The test passes when the TDR curve is within the HDMI specification of 100 Ω ± 15 %
(85 Ω to 115 Ω). The impact of ESD protection is reduced impedance caused by the
capacitance of the ESD protection diode.
The TDR results show the impedance with respect to the geometric position. The HDMI
connector is visible on the left side followed by the impact of the ESD protection device.
The distance between the HDMI connector on the protection device influences the impact
of both components. An inductive connector can partly compensate a capacitance impact
of the protection device.
The signal flow is split up over the paths through the protection device and through the
micro strip lines on the PCB.
sum of
various
reflections
HDMI
CONNECTOR
C
001aag024
Fig 22. Signal flow on PCB and ESD protection device
The impact of the ESD protection device overlaps the impact of the signal track on the
PCB. The impedance change in the TDR measurement graph can give the impression
that the impact is behind the device because the length of the signal inside the device is
longer than the signal track underneath the device. To compensate the impact of the ESD
protection device, the impedance of the micro strip lines can have a higher value (110 Ω
instead of 100 Ω), which is still within the impedance window of 85 Ω to 115 Ω to fulfill the
HDMI specification.
The HDMI connector increases the impedance with an inductive load; the protection
device reduces the impedance with a capacitive load. The distance between the HDMI
connector and the protection device can fine-tune the impedance because of the mutual
compensation of these inductive and capacitive loads.
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8. ESD protection of HDMI transceivers requiring level shifting
(IP4776CZ38)
The IP4776CZ38 is designed for DVI/HDMI interface protection. The IP4776CZ38 also
includes level shifting and backdrive protection. Figure 23 shows the schematics of the
IP4776CZ38 with all necessary and desirable interface isolation functions.
TMDS_D2+
TMDS_D1+
TMDS_BIAS
TMDS_D0+
TMDS_CLK+
VCC(5V0)
TMDS_D2−
TMDS_D1−
TMDS_GND
TMDS_D0−
VCC(3V3) TMDS_BIAS
DDC_CLK_IN
VCC(3V3) TMDS_BIAS
DDC_CLK_OUT
CEC_IN
VCC(3V3) TMDS_BIAS
HOT_PLUG_DET_IN
TMDS_CLK−
CEC_OUT
VCC(3V3) TMDS_BIAS
HOT_PLUG_DET_OUT
DDC_DAT_IN
DDC_DAT_OUT
001aae863
Fig 23. Schematics of the IP4776CZ38
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Features of the IP4776CZ38:
• Pb-free and RoHS compliant
• Integrated high-level ESD protection, level shifting and backdrive protection
• All TMDS lines with integrated rail-to-rail clamping diodes with downstream ESD
protection of ±8 kV contact according to IEC 61000-4-2, level 4 standard
• Matched 0.5 mm trace spacing
• Bidirectional level shifting N-channel FETs provided for DDC clock and DDC data
channels
•
•
•
•
•
TMDS lines with ≤ 0.05 pF matching of capacitance between the TMDS pairs
Line capacitance < 1 pF per channel
Backdrive protection
Dedicated 38-pin TSSOP lead-free package for high-speed signals
Compliant with HDMI 1.2 and HDMI 1.3 specification
One of the main advantages of such an integrated solution is that the IP4776CZ38
solution contains a high safety margin with respect to the HDMI TDR measurements
compared to any discrete solutions.
With interfaces operating in the high frequency range, board routing becomes a critical
factor that determines whether the system as a whole will pass or fail the
HDMI-compliance tests. To be HDMI compliant, the channel impedance of the TMDS lines
must be carefully tuned to 100 Ω ± 15 %.
The disadvantage of conventional ESD protection devices such as varistors or standard
diodes is their relatively high capacitive load that either leads to failing of the
HDMI-compliance tests or to significant routing difficulties and various board layouts to
optimize the routing. As such, manufacturers have often used polymer-based protection
devices which provide low line capacitance. The major disadvantage with these
components is their high minimum breakdown voltage, in the range of 150 V and above,
their degradation through ESD strikes, as well as their expense.
The IP4776CZ38 from NXP Semiconductors provides all advantages necessary for the
HDMI interface and adds only very limited capacitive load comparable to polymer-based
protection devices. This component has been successfully tested both by Silicon Image
and NXP Semiconductors internal HDMI testing facility, and due to its very low line
capacitance of 0.7 pF is also compliant with the HDMI 1.3 specification.
8.1 Application schematic and layout proposal (IP4776CZ38)
Figure 24 shows the IP4776CZ38 in the typical application schematic of an HDMI receiver
port (HDMI sink). Figure 25 shows an HDMI transmitter port (HDMI source). The
diagrams demonstrate the connector, the NXP Semiconductors device and the required
external devices for the DDC, CEC and Hot-Plug signals.
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IP4776CZ38
VCC(5V0)
38
1
VCC(3V3)
2
37
GND
3
36
n.c.
C_BYP
TMDS_BIAS
100 nF
35 n.c.
TMDS_D2+ 4
TMDS_GND
GND
TMDS_D2+
TMDS_GND
TMDS_GND
5
34
6
33 TMDS_D2−
TMDS_D2−
32 n.c.
TMDS_D1+
n.c.
TMDS_D1+ 7
TMDS_GND
31
TMDS_GND
8
TMDS_GND
9
30 TMDS_D1−
TMDS_D1−
29 n.c.
TMDS_D0+
n.c.
TMDS_D0+ 10
TMDS_GND
HDMI
RECEIVER
TMDS_GND
11
28
12
27 TMDS_D0−
TMDS_GND
TMDS_D0−
n.c.
TMDS_GND
TMDS_CLK+
26 n.c.
TMDS_CLK+ 13
TMDS_GND
14
25
15
24 TMDS_CLK−
16
23
HDMI
CONNECTOR
TMDS_GND
TMDS_CLK−
n.c.
CEC_IN
CEC_OUT
CEC
n.c.
DDC_CLK_IN
DDC_DAT_IN
HOT_PLUG
_DET_IN
17
22
18
21
19
20
DDC_CLK_OUT
DDC_CLK
DDC_DAT_OUT
DDC_DAT
HOT_PLUG
_DET_OUT
GND
R_HP
1.0 kΩ
R_Clock
47 kΩ
R_CEC
100 kΩ
R_Data
47 kΩ
R_Clock
47 kΩ
1
2
3
4
VCC(3V3)
8
EEPROM
R_CEC
27 kΩ
R_Data
47 kΩ
+5 V
HOT_PLUG
_DET
R 10 kΩ
7
6
C_HP
100 nF
5
R_DDC
100 Ω
VCC(3V3) VCC(5V0)
001aah583
Fig 24. HDMI receiver
Figure 24 and Figure 25 show different configurations for using the IP4776CZ38 with an
HDMI receiver or transmitter. The differences, which relate to the DDC, Hot-Plug and CEC
lines, are explained in Section 4 “Level shifting” and Section 5 “Backdrive protection”. ESD
protection and backdrive protection are used on the DDC, Hot-Plug and CEC lines. DDC
and Hot-Plug lines also use level shifting. At the transmitter side an additional power
limiter device is recommended to limit the 5 V current to 500 mA or less, in case of for
example, a short of the HDMI connector.
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IP4776CZ38
VCC(5V0)
1
38
VCC(3V3)
2
37
3
36
n.c.
C_BYP
TMDS_BIAS
100 nF
GND
TMDS_D2+ 4
TMDS_GND
GND
35 n.c.
TMDS_D2+
TMDS_GND
TMDS_GND
5
34
6
33 TMDS_D2−
TMDS_D2−
32 n.c.
TMDS_D1+
n.c.
TMDS_D1+ 7
TMDS_GND
31
TMDS_GND
TMDS_GND
8
9
30 TMDS_D1−
TMDS_D1−
29 n.c.
TMDS_D0+
n.c.
TMDS_D0+ 10
TMDS_GND
HDMI
TRANSMITTER
TMDS_GND
11
28
12
27 TMDS_D0−
TMDS_GND
TMDS_D0−
n.c.
TMDS_CLK+ 13
TMDS_GND
TMDS_CLK+
26 n.c.
TMDS_GND
TMDS_GND
14
25
15
24 TMDS_CLK−
TMDS_CLK−
16
23
HDMI
CONNECTOR
n.c.
CEC_IN
CEC_OUT
CEC
n.c.
DDC_CLK_IN
DDC_DAT_IN
HOT_PLUG
_DET_IN
R_CEC
100 kΩ
17
22
18
21
19
20
DDC_CLK_OUT
DDC_CLK
DDC_DAT_OUT
DDC_DAT
HOT_PLUG_
DET_OUT
GND
R_Data
47 kΩ
R_CEC
27 kΩ
R_Clock
47 kΩ
R_Data
1.5 kΩ
+5 V
HOT_
PLUG_DET
R_Clock
1.5 kΩ
R_PD
15 kΩ
VCC(3V3)
VCC(3V3) VCC(5V0)
001aah584
Fig 25. HDMI transmitter
For high-frequency applications like HDMI, an accurate layout is of similar importance to
the electrical functionality of the devices (see Section 7 “PCB design”). The reason is that
parasitic capacitance, inductance or mismatched impedance influence the input
impedance, and the input impedance is a very sensitive parameter to fulfill the HDMI
compliance test.
The IP4776CZ38 uses a TSSOP38 package, which makes this accurate layout for HDMI
very simple. The IP4776CZ38 should be mounted close to the HDMI interface for
maximum ESD protection efficiency. The choice of the package and the pinning chosen
allows a straight routing of the TMDS lines through the package, thereby limiting potential
parasitic inductance generated by complex routing.
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8.2 TDR measurements (IP4776CZ38)
HDMI-compliance tests have been performed at NXP Semiconductors and Silicon Image
compliance test centers. The compliance test specification requires the input impedance
of the TMDS lines to be 100 Ω ± 15 Ω. To fulfill this requirement, the ESD protection
device has to present a very low line capacitance. With the IP4776CZ38, NXP
Semiconductors has achieved an ultra-low line capacitance of 0.7 pF typical. In order to
demonstrate the excellent low line capacitance, TDR measurements were performed also
at 75 ps and 35 ps (unfiltered) TDR step rise times, in addition to the standard 200 ps rise
times. As shown in Figure 26, the IP4776CZ38 easily passes at 200 ps, 100 ps and even
if ‘no filter’ condition is used. Due to the very low line capacitance of the IP4776CZ38,
customers can use a more relaxed PCB design. Furthermore, this low line capacitance
allows full compliance with the HDMI 1.3 specification.
125 Ω
125 Ω
IP4776CZ38
IP4776CZ38
115 Ω
115 Ω
no filter
no filter
filter[200ps]
100 Ω
impedance
compliance
with
HDMI spec
filter[200ps]
100 Ω
85 Ω
filter[75ps]
impedance
compliance
with
HDMI spec
85 Ω
filter[75ps]
75 Ω
75 Ω
time [50 ps/div]
time [50 ps/div]
001aaf216
a. TMDS clock
001aaf217
b. TMDS D0
125 Ω
IP4776CZ38
125 Ω
IP4776CZ38
115 Ω
115 Ω
no filter
no filter
filter[200ps]
100 Ω
impedance
compliance
with
HDMI spec
filter[200ps]
100 Ω
85 Ω
filter[75ps]
85 Ω
filter[75ps]
75 Ω
time [50 ps/div]
impedance
compliance
with
HDMI spec
75 Ω
time [50 ps/div]
001aaf218
c. TMDS D1
001aaf219
d. TMDS D2
Fig 26. TDR measurements at NXP Semiconductors
The TDR step rise times were varied with mathematical filter options on the TDR
equipment. The TDR measurements depicted in Figure 26 were performed at NXP
Semiconductors and show the upper and lower HDMI specification limit indicated by lines
at 115 Ω and 85 Ω. Clearly the IP4776CZ38 is well within the limits.
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In addition to the TDR measurements at NXP Semiconductors, those at Silicon Image
shown in Figure 27 show the highest and lowest impedance as measured for the
IP4776CZ38. Also in these measurements, the IP4776CZ38 is well within the HDMI
specification limits.
105 Ω
M1
105 Ω
M1
93 Ω
90 Ω
time [520 ps/div]
time [520 ps/div]
001aaf220
a. TMDS clock
001aaf221
b. TMDS D0
105 Ω
M1
107 Ω
M1
92 Ω
90 Ω
time [520 ps/div]
time [520 ps/div]
001aaf222
c. TMDS D1
001aaf223
d. TMDS D2
Fig 27. TDR measurements at Silicon Image
The step increase of the impedance shown at the right side is due to the open-end
structure on the measurement board.
8.3 Eye diagram measurements (IP4776CZ38)
Another important measurement of the quality of the transmission signals are the Eye
diagram measurements. The minimum eye opening is defined by the CTS octagons in
Figure 28. Any ESD protection influences the signal due to the internal parasitic
resistance and capacitance. For the high-frequency HDMI design, it is important that the
ESD protection has a minimum parasitic capacitance to pass the HDMI specification. The
Eye diagram measurements in Figure 28 were performed at NXP Semiconductors and
show the influence of the IP4776CZ38. To demonstrate the parasitic influence, identical
measurements have been performed with and without the IP4776CZ38 chip on the same
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HDMI, DVI interface protection
board. The measurement results underline a negligible increase of the data jitter by only
3.5 ps due to the parasitic impact of the IP4776CZ38. The IP4776CZ38 effectively has no
impact on the Eye pattern.
861 m
855 m
voltage
[172 mV/div]
voltage
[171 mV/div]
−855 m
−861 m
0
time [269 ps/div]
2.69 n
0
time [269 ps/div]
001aaf225
001aaf224
a. Measured without IP4776CZ38
2.69 n
b. Measured with IP4776CZ38
Fig 28. Eye diagram measurements
The signal frequencies at the TMDS lines (D0, D1 and D2) are about 10 times the pixel
clock of the video signal. The frequency of the pixel clock depends on the video resolution
selected. The minimum value is 25 MHz for PAL (720 × 576i) and NTSC (720 × 480i) at
standard resolution with pixel repetition (250 MHz on TMDS lines). The maximum pixel
clock is 74.25 MHz for HDTV (1920 × 1080i, 742.5 MHz on TMDS lines). The upcoming
1080p format will double the pixel clock frequency to 148.50 MHz (1.5 GHz at TMDS
lines) and the new 10-bit color format will enhance the pixel clock frequency to about
200 MHz (2 GHz at TMDS lines).
8.4 Pulse clamping performance (IP4776CZ38)
Following the two ESD standards, HBM and IEC 61000-4-2, the clamping voltage of the
TMDS lines is measured. The results of measurements shown in Figure 29 indicate a
maximum clamping voltage of 18.2 V for the HBM and 37.6 V for IEC 61000-4-2 level 4.
HDMI transceivers (standalone or integrated) typically have a 2 kV internal ESD
protection. The low maximal clamping voltage of the IP4776CZ38 reduces the ESD
strikes so that the total HDMI system easily survives high-energy ESD pulses according to
the IEC 61000-4-2 level 4 standard.
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HDMI, DVI interface protection
001aaf226
60
voltage
(V)
20
−20
−60
−100
−20
20
60
100
140
time (ns)
a. ESD clamping example (IEC 61000-4-2 −8 kV)
001aaf227
100
voltage
(V)
60
20
−20
−60
−20
20
60
100
140
time (ns)
b. ESD clamping example (IEC 61000-4-2 +8 kV)
Fig 29. Clamping voltages
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9. Summary
For a high-speed interface such as DVI or HDMI, the use of high-level ESD protection is
highly recommended. The cost of applications such as a digital TV or a Set-Top Box is
simply too high to risk field returns. A fail can also damage company brand name and
image. The continuous trend towards sub-micron CMOS processes at 120 nm, 90 nm,
65 nm and 45 nm technology nodes also contributes to a very high sensitivity of core ICs,
making ESD protection mandatory.
The high-speed ESD protection devices discussed in this application note fully comply
with both crucial requirements:
• The high-level ESD protection according to the international standards for consumer
applications (IEC 61000-4-2 level 4)
• The ultra-low line capacitance requirement for the HDMI high-speed lines are fully
achieved
The additional functions of level shifting and backdrive protection, integrated in an
optimized package for HDMI applications, give the IP4776CZ38 an optimum level of
integration. This package allows and supports optimal routing of the TMDS lines to
minimize parasitic influences.
The NXP Semiconductors high-speed ESD protection devices are fully compliant with
HDMI, and support easy routing and relaxed board layout at the highest protection levels.
Therefore these devices are regarded as a protection standard of choice to be
implemented on all new customer designs.
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10. Abbreviations
Table 4.
Abbreviations
Acronym
Description
ATC
Authorized Testing Center
CEC
Consumer Electronics Control
CTS
Compliance Test Specifications
DDC
Data Display Channel
DTV
Digital TeleVision
DUT
Device Under Test
DVD
Digital Versatile Disc
DVI
Digital Visual Interface
EDID
Extended Display Identification Data
ESD
ElectroStatic Discharge
FET
Field Effect Transistor
GPIO
General Purpose Input/Output
HBM
Human Body Model
HDCP
High-bandwidth Digital Content Protection
HDMI
High-Definition Multimedia Interface
HDTV
High-Definition TeleVision
IEC
International Electrotechnical Commission
I/O
Input/Output
MSL
Micro Strip Line
NMOS
n-type Metal-Oxide Semiconductor
NTSC
National Television Standards Committee
PAL
Phase Alternate Line
PCB
Printed-Circuit Board
RoHS
Restriction of the use of certain Hazardous Substances
RC
Resistor Capacitor
STB
Set-Top Box
TDR
Time Domain Reflection
TMDS
Transition Minimized Differential Signaling
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11. Legal information
11.1 Definitions
Draft — The document is a draft version only. The content is still under
internal review and subject to formal approval, which may result in
modifications or additions. NXP Semiconductors does not give any
representations or warranties as to the accuracy or completeness of
information included herein and shall have no liability for the consequences of
use of such information.
Suitability for use — NXP Semiconductors products are not designed,
authorized or warranted to be suitable for use in medical, military, aircraft,
space or life support equipment, nor in applications where failure or
malfunction of an NXP Semiconductors product can reasonably be expected
to result in personal injury, death or severe property or environmental
damage. NXP Semiconductors accepts no liability for inclusion and/or use of
NXP Semiconductors products in such equipment or applications and
therefore such inclusion and/or use is at the customer’s own risk.
Applications — Applications that are described herein for any of these
products are for illustrative purposes only. NXP Semiconductors makes no
representation or warranty that such applications will be suitable for the
specified use without further testing or modification.
11.2 Disclaimers
General — Information in this document is believed to be accurate and
reliable. However, NXP Semiconductors does not give any representations or
warranties, expressed or implied, as to the accuracy or completeness of such
information and shall have no liability for the consequences of use of such
information.
Right to make changes — NXP Semiconductors reserves the right to make
changes to information published in this document, including without
limitation specifications and product descriptions, at any time and without
notice. This document supersedes and replaces all information supplied prior
to the publication hereof.
11.3 Trademarks
Notice: All referenced brands, product names, service names and trademarks
are the property of their respective owners.
I2C-bus — logo is a trademark of NXP B.V.
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12. Tables
Table 1.
Table 2.
Table 3.
Table 4.
IEC 61000-4-2 ESD surge classification[1] . . . . .5
MIL-883E method 3015.7 ESD surge
classification, contact discharge . . . . . . . . . . . .6
Parameters for 2- and 4-layer PCB (FR4) . . . .17
Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . .28
continued >>
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13. Figures
Fig 1.
Fig 2.
Fig 3.
Fig 4.
Fig 5.
Fig 6.
Fig 7.
Fig 8.
Fig 9.
Fig 10.
Fig 11.
Fig 12.
Fig 13.
Fig 14.
Fig 15.
Fig 16.
Fig 17.
Fig 18.
Fig 19.
Fig 20.
Fig 21.
Fig 22.
Fig 23.
Fig 24.
Fig 25.
Fig 26.
Fig 27.
Fig 28.
Fig 29.
Test circuit according IEC 61000-4-2 . . . . . . . . . . .4
ESD surge according IEC 61000-4-2. . . . . . . . . . .5
Test circuit according to MIL-883E method
3015.7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
ESD surge according to MIL-883E method
3015.7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Rail-to-rail diode concept as used by NXP
Semiconductors achieves ultra-low line
capacitance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Principles of I2C-bus level shifter . . . . . . . . . . . . . .8
Measurements of I2C-bus level shifter . . . . . . . . . .9
Output difference voltage at level shifter . . . . . . . .9
DDC application with level shift to 3.3 V and
ESD protection. . . . . . . . . . . . . . . . . . . . . . . . . . .10
DDC application with ESD protection . . . . . . . . .10
CEC application with level shift to low voltage
and ESD protection . . . . . . . . . . . . . . . . . . . . . . .11
CEC application with ESD protection. . . . . . . . . .11
Principles of the Hot-Plug signal . . . . . . . . . . . . .11
Hot-Plug, level shift and backdrive protection . . .12
Principles of backdrive protection . . . . . . . . . . . .13
Backdrive protection at DDC bus . . . . . . . . . . . . .13
IP4280CZ10. . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
IP4776CZ38 with ESD and backdrive
protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
Reference board IP4776CZ38 . . . . . . . . . . . . . . .15
Test structure PCB (principles) . . . . . . . . . . . . . .16
Geometrics for TMDS lines . . . . . . . . . . . . . . . . .17
Signal flow on PCB and ESD protection device. .18
Schematics of the IP4776CZ38 . . . . . . . . . . . . . .19
HDMI receiver . . . . . . . . . . . . . . . . . . . . . . . . . . .21
HDMI transmitter . . . . . . . . . . . . . . . . . . . . . . . . .22
TDR measurements at NXP Semiconductors . . .23
TDR measurements at Silicon Image . . . . . . . . .24
Eye diagram measurements . . . . . . . . . . . . . . . .25
Clamping voltages . . . . . . . . . . . . . . . . . . . . . . . .26
continued >>
AN10495_1
Application note
© NXP B.V. 2007. All rights reserved.
Rev. 01 — 18 December 2007
31 of 32
AN10495
NXP Semiconductors
HDMI, DVI interface protection
14. Contents
1
2
2.1
2.2
2.3
3
4
4.1
4.2
4.3
5
6
7
7.1
7.2
8
8.1
8.2
8.3
8.4
9
10
11
11.1
11.2
11.3
12
13
14
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
ESD protection standards . . . . . . . . . . . . . . . . . 4
IEC 61000-4-2 . . . . . . . . . . . . . . . . . . . . . . . . . 4
Human Body Model (HBM, MIL-883E method
3015.7) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Comparison of IEC and MIL standard . . . . . . . 7
Rail-to-rail concept . . . . . . . . . . . . . . . . . . . . . . 8
Level shifting . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
DDC bus level shifting. . . . . . . . . . . . . . . . . . . 10
CEC bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Hot-Plug application . . . . . . . . . . . . . . . . . . . . 11
Backdrive protection . . . . . . . . . . . . . . . . . . . . 13
ESD protection of HDMI transceivers not
requiring level shifting . . . . . . . . . . . . . . . . . . 14
PCB design. . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Geometry of micro strip lines (TMDS) . . . . . . 17
TDR measurements of the IP4280CZ10 . . . . 18
ESD protection of HDMI transceivers
requiring level shifting (IP4776CZ38). . . . . . . 19
Application schematic and layout proposal
(IP4776CZ38) . . . . . . . . . . . . . . . . . . . . . . . . . 20
TDR measurements (IP4776CZ38) . . . . . . . . 23
Eye diagram measurements (IP4776CZ38) . . 24
Pulse clamping performance (IP4776CZ38). . 25
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Legal information. . . . . . . . . . . . . . . . . . . . . . . 29
Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Disclaimers . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Trademarks . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Please be aware that important notices concerning this document and the product(s)
described herein, have been included in section ‘Legal information’.
© NXP B.V. 2007.
All rights reserved.
For more information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: [email protected]
Date of release: 18 December 2007
Document identifier: AN10495_1
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