Texas Instruments | TMDS Clock Detection Solution in HDMI Sink Applications | Application notes | Texas Instruments TMDS Clock Detection Solution in HDMI Sink Applications Application notes

Texas Instruments TMDS Clock Detection Solution in HDMI Sink Applications Application notes
Application Report
SLLA367 – August 2017
TMDS Clock Detection Solution in HDMI® Sink
Applications TS3USB3031, SN65LVDS4, SN65LVDS17
Gibson Kim
ABSTRACT
High-Definition Multimedia Interface (HDMI®) sink applications such as digital TVs, monitors, and other
display equipment are able to wake up from standby or sleep mode by detecting Transition-Minimized
Differential Signaling (TMDS) clock or signals in HDMI applications.
1
2
3
Contents
Waking Up an HDMI Sink Device ......................................................................................... 2
Communicating Without CEC .............................................................................................. 3
Conclusion .................................................................................................................... 8
List of Figures
1
HDMI High-Level Block Diagram .......................................................................................... 2
2
Conceptional Schematic for one TMDS Differential Pair ............................................................... 3
3
Implementation Example Block Diagram 1 ............................................................................... 4
4
Implementation Example Block Diagram 2 - Single-Chip Implementation ........................................... 5
5
Q-Signal Boost Circuitry Suggestion ...................................................................................... 6
6
Q-Signal Boost Circuitry for Simulation ................................................................................... 6
7
Typical Waveforms From Simulation ...................................................................................... 7
8
Single Remote Controller for Both HDMI Sink and Source ............................................................ 8
List of Tables
1
CEC Operation Codes ...................................................................................................... 2
2
Termination Requirement in HDMI Receiver ............................................................................. 3
3
Summary of Simulation Result for Corner Cases ....................................................................... 7
4
HDMI Sink can Wake-Up Without CEC ................................................................................... 8
Trademarks
Blu-ray Disk is a trademark of Blu-ray Disc Association.
HDMI is a registered trademark of HDMI Licensing, LLC.
All other trademarks are the property of their respective owners.
SLLA367 – August 2017
Submit Documentation Feedback
TMDS Clock Detection Solution in HDMI® Sink Applications
Copyright © 2017, Texas Instruments Incorporated
1
Waking Up an HDMI Sink Device
1
www.ti.com
Waking Up an HDMI Sink Device
HDMI is a defacto interface standard in consumer electronics and the most successful and easiest video
and audio connector in the industry. Most digital TVs, monitors, and video display equipment have one or
more HDMI ports. Video source equipment such as set-top boxes, gaming consoles, Blu-ray Disk™
players, notebooks, and mobile video sources support HDMI as well.
HDMI supports a supplemental specification, Consumer Electronics Control (CEC), to control the HDMI
source and sink in HDMI-connected equipment. CEC provides the same ‘language’ between the HDMI
equipment allowing users to easily control them. Figure 1 shows the high-level HDMI interconnection,
including a CEC line.
Video
Video
TMDS Channel 0
TMDS Channel 1
Audio
HDMI
Transmitter
Control/Status
TMDS Channel 2
HDMI
Transmitter
TMDS Clock Channel
Display Data Channel (DDC)
CEC Line
CEC
Audio
Control/Status
EDID
ROM
CEC
Utility Line
HEAC
HEAC
detect
HPD Line
High / Low
Figure 1. HDMI High-Level Block Diagram
CEC is one of the 19 HDMI connector pins and CEC has its own electrical and protocol specification. A
number of different messages and operation code (opcode) are used for the best user experience so that
users can use only one remote controller to control both HDMI source and HDMI sink devices. For
instance, if an HDMI source and sink are in standby mode and the user wants to wake up both of them,
the following power-on function code can be used to switch on the HDMI devices by pressing the power
button on the remote controller. This will wake up both the HDMI source and sink devices. More advanced
user-controlled CEC messages are available, refer to the CEC specification in HDMI 2.0, or older version
specifications.
Table 1. CEC Operation Codes
2
UI Command Code
User Operation
Function
0x6C
Power off function
Puts the device into the Standby state. If repeated, the device stays in the Standby
state.
0x6D
Power on function
Puts the device into the On (non-Standby) state. If repeated, the device stays in the
active state.
TMDS Clock Detection Solution in HDMI® Sink Applications
Copyright © 2017, Texas Instruments Incorporated
SLLA367 – August 2017
Submit Documentation Feedback
Waking Up an HDMI Sink Device
www.ti.com
1.1
Reasons for Wake Up Failure
Although CEC is provided for the control of the HDMI devices, its implementation and operation is not that
simple. It is common that HDMI sink users experience the HDMI source is not controllable through a
single remote controller as expected, and vice versa. This is because many HDMI sources and sinks do
not support CEC, including a few very well-known HDMI source devices and thus there is no simple way
to control both the HDMI source and sink devices at once. There are also a number of HDMI devices
supporting CEC, but require complicated steps to enable the feature in the equipment. Not as common
are some devices that implement vendor-specific codes preventing HDMI source and sink devices from
communicating.
2
Communicating Without CEC
This section provides examples for making the HDMI sink device detect Transition Minimized Differential
Signaling (TMDS) clock or signal from an HDMI source device so that the HDMI sink can wake up from its
standby state by turning on the HDMI source with a single remote controller.
The HDMI transmitter source detects receiver terminations in HDMI sink. If the HDMI receiver enables the
termination resistors, then the transmitter will determine the 3.3-V terminated level and that the receiver is
connected and functioning.
AVCC
Transmitter
D
RT
RT
D
Current
Source
Receiver
Figure 2. Conceptional Schematic for one TMDS Differential Pair
Table 2. Termination Requirement in HDMI Receiver
SLLA367 – August 2017
Submit Documentation Feedback
Item
Value
Termination supply voltage, AVCC
3.3 V ±5%
Termination resistance, RT
50 Ω ±5%
TMDS Clock Detection Solution in HDMI® Sink Applications
Copyright © 2017, Texas Instruments Incorporated
3
Communicating Without CEC
www.ti.com
When an HDMI sink is in standby mode, most HDMI sinks will disable the termination resistors to save
power while enabling a Hot-Plug Detection (HPD) signal (high) as long as an HDMI source plug is
providing HDMI 5 V. The HDMI source will have no way to provide a TMDS signal and wake up the sink,
because they are not terminated.
2.1
Implementation Example 1: TS3USB3031, SN65LVDS4
HDMI SINK
6WDQGE\ : $FWLYH
TS3USB3031 VBIAS
TMDS_CLK+
TMDS_CLK-
STANDBY
IN
OUT1 +
IN
OUT1 -
6WDQGE\ : :$.(-UP
SN65LVDS4
CK_DET signal
RTerm
MCU
C
Bias
Circuit
RC filter
B
Wake Up
E
OUT2 +
OUT2 -
ACTIVE
HDMI Rx
HDMI Connector
HDMI SOURCE
TMDS_DATA 0
TMDS_DATA 1
TMDS_DATA 2
HDMI Tx
Video
Processor
DDC_SCL
DDC_SDA
Figure 3. Implementation Example Block Diagram 1
This is proven by simulation and actual test board environment for both functionality and HDMI
compliance test at different corner cases:
• A high-speed switch can be used to switch or isolate actual TMDS clock path from TMDS clock
detection path. In Active mode, TMDS clock can be connected to HDMI Rx in a video processor. In
Standby mode, it is directed to TMDS clock and signal detection circuitry to check if there is an
incoming signal or not.
• Use caution when selecting a high-speed switch. In order to fulfill signal integrity and HDMI compliance
test, the electrical characteristics of the switch are important. The TS3USB3031 provides a good
enough bandwidth and I/O capacitance up to 4K/60fps video conditions. A good layout technique is
required to minimize impact to the impedance - HDMI spec: 100 Ω ±15% with single excursion of 100
Ω ±25% with duration less than 250 ps.
• Proper termination for HDMI source to see RTerm in the standby mode of the HDMI sink is needed.
• Differential to single-ended receiver can be used to convert TMDS clock signals to single-ended TTL or
CMOS signals. A proper bias circuitry may be needed for TMDS to the Differential to single-ended
receiver. The SN65LVDS4 has a wide-enough bandwidth, VID and sensitivity spec so that TMDS clock
rates from all video resolutions can be converted to single-ended signal.
• Depending on the MCU or processor that will detect the wake-up signal from SN65LVDS4, a proper
RC filtering may be needed to eventually detect the wake-up signal. If the MCU or processor can
detect the clock signal itself, this step is not needed.
• A proper transistor may be used to meet I/O spec of the MCU.
• Once the wake-up signal is detected, then the MCU wakes up the video processor and the video
processor can enable RTerm in HDMI Rx for normal operation.
4
TMDS Clock Detection Solution in HDMI® Sink Applications
Copyright © 2017, Texas Instruments Incorporated
SLLA367 – August 2017
Submit Documentation Feedback
Communicating Without CEC
www.ti.com
2.2
Implementation Example 2: SN65LVDS17
HDMI SINK
6WDQGE\ : $FWLYH
6WDQGE\ : :$.(-UP
SN65LVDS17
Signal Boost Circuitry
See. Fig 7
CK_DET signal
MCU
4 mA
TMDS_CLK+
Y
Z
VREF
Wake Up
VCC
TMDS_DATA 0
HDMI Rx
HDMI Connector
HDMI SOURCE
TMDS_CLK-
A
B
TMDS_DATA 1
TMDS_DATA 2
Video
Processor
DDC_SCL
HDMI Tx
DDC_SDA
Figure 4. Implementation Example Block Diagram 2 - Single-Chip Implementation
This is proven by simulation and actual test board environment for both functionality and HDMI
compliance test at different corner cases.
• Products like the SN65LVDS17 can be used to detect TMDS clock. SN65LVDS17 supports wide
enough bandwidth up to 2 GHz for TMDS clock. It senses clock signals and transmits Q output with
575-mV peak-to-peak output voltage.
• Proper termination for HDMI source to see RTerm in standby mode of HDMI Sink is needed. AC
coupling caps are required between SN65LVDS17 to HDMI Rx.
• Depending on the MCU or processor that will detect the wake-up signal from SN65LVDS17, a proper
circuitry at Q output may be needed to eventually detect the wake-up signal. If the MCU or processor
can detect the Q signal of the SN65LVDS17 itself, this step is not needed.
• Once the wake-up signal is detected, then the MCU wakes up the video processor and the video
processor can enable RTerm in HDMI Rx for normal operation.
The following list is a circuit suggestion to boost up Q output from SN65LVDS17 and to provide a proper
clock detection signal to the MCU. It is required to have transistors with enough bandwidth and accurate
pull up and pull down the design (R5 and R6) depending on the transistor (QN2).
• C1 allows decoupling of the LVDS17 output bias to avoid issues from part-to-part variations
• R1 and R2 to bias QN1
• QN1 has to have enough BW to pass a maximum of 340-MHz signals
• R3 and R4 provide gain
• C2 and R5 ensure QN2 is always off and no leakage occurs when there is no clock signal
• QN2 has to have enough BW to pass 340-MHz signals
• R6 and C3 determine how fast the circuit will determine clock presence or absence
• MMBT5179 or similar performance transistors are good choices
SLLA367 – August 2017
Submit Documentation Feedback
TMDS Clock Detection Solution in HDMI® Sink Applications
Copyright © 2017, Texas Instruments Incorporated
5
Communicating Without CEC
www.ti.com
R1
R3
R5
R7
C1
CKDET#
QN1
R2
R4
R6
QN2
C3
SN65LVDS17
Q
Design Parameter Suggestion
oooQN1 = MMBT5179TR-ND
oooQN2 = MMBT5179TR-ND
oooR1 = 11 kΩ
oooR2 = 5.6 kΩ
oooR3 = 330 Ω
oooR4 = 0 Ω (can be removed)
oooR5 = 33 kΩ (must be ±1%)
oooR6 = 6.2 kΩ (must be ±1%)
oooR7 = 51 kΩ
oooC1 = 1 nF
oooC2 = 1 nF
oooC3 = 1 nF
4 mA
A
B
88
Y
Z
VREF
VCC
EN
Figure 5. Q-Signal Boost Circuitry Suggestion
Simulation has been done with the circuit shownin Figure 6 at different corner conditions.
Figure 6. Q-Signal Boost Circuitry for Simulation
6
TMDS Clock Detection Solution in HDMI® Sink Applications
Copyright © 2017, Texas Instruments Incorporated
SLLA367 – August 2017
Submit Documentation Feedback
Communicating Without CEC
www.ti.com
Figure 7 shows the waveform from a simulation with a clock input of 70-mV swing under typical
temperature and Vcc conditions.
Figure 7. Typical Waveforms From Simulation
TI completed a simulation with corner cases and the results suggest that a well-designed circuit with
pullup and pulldown resistors (R5 and R6) and Vcc with 1% tolerance will allow the MCU to detect signals
with down to a 70-mV swing level under 0–70°C temperature conditions.
Table 3. Summary of Simulation Result for Corner Cases
SLLA367 – August 2017
Submit Documentation Feedback
TMDS Clock Detection Solution in HDMI® Sink Applications
Copyright © 2017, Texas Instruments Incorporated
7
Conclusion
3
www.ti.com
Conclusion
With a TMDS clock or signal-detection circuitry implemented, the HDMI source can determine TMDS
receiver termination and transmit clock and signal when the user activates the source from its standby
mode, and eventually HDMI sink can detect TMDS clock or signal running and wake up the system
without any control.
Table 4. HDMI Sink can Wake-Up Without CEC
Device Power State No CEC Supported
Without TMDS Clock Detector
With TMDS Detector
HDMI Sink
HDMI Source
RTerm
Source Remote
Control Causes
Wake-Up
RTerm
Source Remote
Control Causes
Wake-Up
Active
Active
Yes
-
Yes
-
Active
Standby
Yes
-
Yes
-
Standby
Active
No
No
Yes
Yes
Standby
Standby
No
No
Yes
Yes
Figure 8. Single Remote Controller for Both HDMI Sink and Source
8
TMDS Clock Detection Solution in HDMI® Sink Applications
Copyright © 2017, Texas Instruments Incorporated
SLLA367 – August 2017
Submit Documentation Feedback
IMPORTANT NOTICE FOR TI DESIGN INFORMATION AND RESOURCES
Texas Instruments Incorporated (‘TI”) technical, application or other design advice, services or information, including, but not limited to,
reference designs and materials relating to evaluation modules, (collectively, “TI Resources”) are intended to assist designers who are
developing applications that incorporate TI products; by downloading, accessing or using any particular TI Resource in any way, you
(individually or, if you are acting on behalf of a company, your company) agree to use it solely for this purpose and subject to the terms of
this Notice.
TI’s provision of TI Resources does not expand or otherwise alter TI’s applicable published warranties or warranty disclaimers for TI
products, and no additional obligations or liabilities arise from TI providing such TI Resources. TI reserves the right to make corrections,
enhancements, improvements and other changes to its TI Resources.
You understand and agree that you remain responsible for using your independent analysis, evaluation and judgment in designing your
applications and that you have full and exclusive responsibility to assure the safety of your applications and compliance of your applications
(and of all TI products used in or for your applications) with all applicable regulations, laws and other applicable requirements. You
represent that, with respect to your applications, you have all the necessary expertise to create and implement safeguards that (1)
anticipate dangerous consequences of failures, (2) monitor failures and their consequences, and (3) lessen the likelihood of failures that
might cause harm and take appropriate actions. You agree that prior to using or distributing any applications that include TI products, you
will thoroughly test such applications and the functionality of such TI products as used in such applications. TI has not conducted any
testing other than that specifically described in the published documentation for a particular TI Resource.
You are authorized to use, copy and modify any individual TI Resource only in connection with the development of applications that include
the TI product(s) identified in such TI Resource. NO OTHER LICENSE, EXPRESS OR IMPLIED, BY ESTOPPEL OR OTHERWISE TO
ANY OTHER TI INTELLECTUAL PROPERTY RIGHT, AND NO LICENSE TO ANY TECHNOLOGY OR INTELLECTUAL PROPERTY
RIGHT OF TI OR ANY THIRD PARTY IS GRANTED HEREIN, including but not limited to any patent right, copyright, mask work right, or
other intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information
regarding or referencing third-party products or services does not constitute a license to use such products or services, or a warranty or
endorsement thereof. Use of TI Resources may require a license from a third party under the patents or other intellectual property of the
third party, or a license from TI under the patents or other intellectual property of TI.
TI RESOURCES ARE PROVIDED “AS IS” AND WITH ALL FAULTS. TI DISCLAIMS ALL OTHER WARRANTIES OR
REPRESENTATIONS, EXPRESS OR IMPLIED, REGARDING TI RESOURCES OR USE THEREOF, INCLUDING BUT NOT LIMITED TO
ACCURACY OR COMPLETENESS, TITLE, ANY EPIDEMIC FAILURE WARRANTY AND ANY IMPLIED WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND NON-INFRINGEMENT OF ANY THIRD PARTY INTELLECTUAL
PROPERTY RIGHTS.
TI SHALL NOT BE LIABLE FOR AND SHALL NOT DEFEND OR INDEMNIFY YOU AGAINST ANY CLAIM, INCLUDING BUT NOT
LIMITED TO ANY INFRINGEMENT CLAIM THAT RELATES TO OR IS BASED ON ANY COMBINATION OF PRODUCTS EVEN IF
DESCRIBED IN TI RESOURCES OR OTHERWISE. IN NO EVENT SHALL TI BE LIABLE FOR ANY ACTUAL, DIRECT, SPECIAL,
COLLATERAL, INDIRECT, PUNITIVE, INCIDENTAL, CONSEQUENTIAL OR EXEMPLARY DAMAGES IN CONNECTION WITH OR
ARISING OUT OF TI RESOURCES OR USE THEREOF, AND REGARDLESS OF WHETHER TI HAS BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES.
You agree to fully indemnify TI and its representatives against any damages, costs, losses, and/or liabilities arising out of your noncompliance with the terms and provisions of this Notice.
This Notice applies to TI Resources. Additional terms apply to the use and purchase of certain types of materials, TI products and services.
These include; without limitation, TI’s standard terms for semiconductor products http://www.ti.com/sc/docs/stdterms.htm), evaluation
modules, and samples (http://www.ti.com/sc/docs/sampterms.htm).
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2017, Texas Instruments Incorporated
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertising