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Texas Instruments ESD Protection for HDMI Interfaces Application notes
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ESD Protection for HDMI Applications
Matthew Xiong
Since its creation in 2002, High-Definition Multimedia
Interface (HDMI) has remained one of the most
popular interfaces for transmitting video and audio
data. With each HDMI standard update, improvements
in process technology have allowed manufacturers to
increase data bandwidth and add additional features in
smaller and smaller chipsets. However, with this
decrease in size, HDMI components have become
more sensitive to transient voltages such as
electrostatic discharge. This has created a need for
ESD protection that clamp at very low voltages without
compromising high speed signal integrity.
Figure 1. Pinout of the HDMI Receptacle
Figure 2. 6-channel TVS diode array (top) vs. 1channel TVS diodes (bottom) for non-TMDS
protection
In the HDMI connector (figure 1), there are four
differential pairs of transmission minimized digital
signaling (TMDS) channels. For HDMI 2.0, three
TMDS pairs (TMDS0, TMDS1 and TMDS2) are
responsible for transferring millions of pixels of data
per second while the TMDS CL pair provides the
clocking signal to synchronize this information.
On the other hand, the TMDS channels pass
differential data that can reach 18Gbps (6Gbps for
each pair) for HDMI 2.0, with a maximum single-ended
operating voltage of 3.3V on each differential line. As a
result, the ESD protection diodes that are placed on
these high speed traces must have low enough
capacitance to maintain signal integrity and meet the
HDMI compliance standard.
Apart from the four TMDS pairs, the HDMI connector
also has six other channels: The hot plug detect (HPD)
channel senses when a connection is established, the
consumer electronic control (CEC) channel allows
users to control devices through HDMI, the utility
channel can be used for HDMI Ethernet or an audio
return channel, the SDA and SCL channels provide
I2C control, and the final channel provides 5V of
power.
Due to the sensitive nature of the TMDS I/O pins,
clamping voltage must also be minimized for TMDS
ESD protection. This is accomplished by selecting an
ESD diode that has an ultra low dynamic resistance
(RDYN) so when an ESD strike is present, the diode
provides a low impedance path to steer current away
from sensitive circuitry downstream.
To protect against ESD failure, a 5V working voltage,
6-channel TVS diode such as the TPD6E05U06 can
be placed on the non-TMDS channels by the HDMI
connector (5V power, SDA, SCL, HPD, CEC and
utility). 5V working voltage, 1-channel TVS diodes
(TPD1E05U06) can also be used here for layout
flexibility. Since these non-TMDS channels do not
pass high speed data, minimizing the capacitance of
the diodes is usually not a concern.
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However, ESD RDYN and capacitance have an inverse
relationship. Increasing the diode junction area would
decrease the RDYN but increase the diode capacitance
which may degrade signal integrity. As a result,
selecting TVS diodes that protect the TMDS channels
without compromising the data transfer is challenging.
In spite of this, the ESD224 is a 4-channel ESD
protection device that is able to clamp ±8kV IEC ESD
events to sufficient levels while maintaining an ultralow capacitance by employing TI’s proprietary ESD
ESD Protection for HDMI Applications Matthew Xiong
Copyright © 2018, Texas Instruments Incorporated
1
www.ti.com
process technology. Since there are four pairs of
TMDS channels, two ESD224 protection diodes would
provide the necessary protection on TMDS traces
while passing the signal integrity eye diagram mask
test (Figure 3).
To protect sensitive HDMI 2.0 SoCs such as the
BCM7250 against ESD strikes, the TVS diode must
ensure that the positive clamping voltage does not
exceed 9.15V and the negative clamping voltage does
not exceed -5.71V. Figure 5 shows that the ESD224
provides this protection by clamping an 8kV IEC ESD
strike to 8.1V and a -8kV IEC ESD strike to -5V.
Figure 3. 6Gbps HDMI 2.0 Eye Diagram Without
(top) and With (bottom) ESD224 Protection
The ESD224 is also able to provide the necessary
ESD clamping protection for sensitive HDMI 2.0
redrivers, retimers and chipsets. For example, the
BCM7250 is a Broadcom HDMI 2.0 SoC that fails at a
low transient voltages: 9.15V and -5.71V. In Figure 4,
a 100ns transmission line pulse (TLP) is used to
determine the ESD failure voltage since 100ns is
approximately the length of an IEC ESD pulse.
Figure 5. ESD224 Clamps +8kV ESD Voltage to
8.1V and -8kV ESD to -5V
For a complete HDMI 2.0 solution, 2x ESD224 can be
used to protect the TMDS channels and 6x
TPD1E05U06 can be used to protect the other
channels. If the ultra low clamping performance of the
ESD224 is not required, the TPD4E02B04 can be
used to protect the TMDS channels.
Table 1. Alternative Device Recommendations
Device
Optimized Parameters
Performance TradeOff
TPD4E02B04
0.25pF capacitance, flow
through routing
Higher clamping
voltage
TPD4E05U06
5V working voltage, flow
through routing
Higher clamping
voltage
ESD204
30kV/30kV IEC rating, 5.5A
surge protection, flow
through routing
Higher capacitance
Related Documentation
Figure 4. BCM7250 Fails at 9.15V and -5.71V
During ESD Events
System Level ESD Selection Guide
ESD224 HDMI 2.0 Compliance AppNote
ESD Essentials Video Series
2
ESD Protection for HDMI Applications Matthew Xiong
Copyright © 2018, Texas Instruments Incorporated
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