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Technology Brief
MHL™ Technology Brief
Document # SiI-TB-1001
Copyright and Trademark Notice
Copyright © 2008 Silicon Image, Inc. All rights reserved. Silicon Image, the Silicon Image logo, MHL, VastLane, the
VastLane logo, Simplay HD, SiI9223, SiI9224, SiI9226 and SiI9290 are trademarks or, registered trademarks of
Silicon Image, Inc. in the United States and/or other countries. HDMI, and High-Definition Multimedia Interface are
trademarks or registered trademarks of HDMI Licensing, LLC. in the United States and/or other countries. All other
trademarks and registered trademarks are the property of their respective owners in the Unites States and/or other
countries.
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Table of Contents
Introduction – What is MHL technology?...............................................................................................................2
How will consumers benefit from MHL technology?............................................................................................2
How is MHL technology implemented in mobile CE devices? ............................................................................3
Why not just equip the mobile device with HDMI output? ...................................................................................3
Why not just use an analog connection between the dongle and the HDTV?..................................................4
Does MHL technology support CEC?.....................................................................................................................4
In Summary, what are the key features of MHL technology? ..............................................................................5
What Silicon Image products are available that support MHL Technology? .....................................................5
About Silicon Image, Inc..........................................................................................................................................7
Introduction – What is MHL technology?
MHL technology is an audio/video interface that connects portable consumer electronics devices, such as
mobile phones, digital cameras, camcorders and portable media players, to HDTVs using a single cable
via the television’s standard HDMI input port. MHL technology was developed by Silicon Image, Inc., a
founding member of the HDMI standards body and a leading manufacturer of HDMI semiconductors
and intellectual property.
How will consumers benefit from MHL technology?
A tremendous amount of multimedia content, from high-resolution images and short videos to featurelength Hollywood films, is downloaded, captured and/or stored on portable personal entertainment
devices. Unfortunately, when consumers connect these portable devices to an HDTV via standard analog
connections, the picture is often displayed with image quality below standard definition. MHL
technology enabled devices, however, can connect to HDTVs via a standard HDMI port found on most
televisions sold today, allowing users to watch and listen to multimedia content on a large screen in high
definition.
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How is MHL technology implemented in mobile CE devices?
To equip a mobile device with MHL technology, the manufacturer would add an MHL transmitter IC to
the mobile device. Four pins on the device’s connector need to be reserved for audio/visual Transition
Minimized Differential Signaling (TMDS) packets and a single pin is reserved for a control bus, which
supports authentication, A/V format discovery, and various control functions.
Initially, MHL technology enabled mobile devices will connect to the DTV via a docking station or
dongle, which includes an HDMI-to-MHL bridge IC that performs the conversion from the lossless MHL
media format into a standard HDMI compatible signal. The docking station is equipped with a standard
HDMI output connector, allowing the docking station to be plugged directly into HDTVs. The docking
station can also pass AC power through to the mobile device to charge the battery when the device is in
the dock and an optional USB connector will allow the device to exchange data with a PC. DTV
manufacturers may integrate MHL technology compatible HDMI receivers and input processors into
their DTV platforms. These DTVs will be capable of accepting MHL input directly from the mobile
device without needing a docking station bridge.
FIGURE 1: MHL Transmitter, Bridge and HDMI Receiver Implementation
Why not just equip the mobile device with HDMI output?
Physical space for connectors on portable mobile devices such as digital cameras, portable media players
and mobile phones is often extremely limited due to the small form factors of these devices. Mobile
device manufacturers generally prefer to have a single proprietary connector that accommodates AC
power, USB and audio/video transfer. The standard HDMI interface would require 19 pins on this
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connector, which can make the standard HDMI interface difficult to implement on small devices. MHL
technology reduces this pin-count requirement from 19 to five, without compromising audio/video
quality or HDMI compatibility, to allow for a smaller, multi-functional connector.
In addition to connector size limitations, an IC’s power requirement is another important consideration
for mobile device manufacturers because this affects battery life, a feature that significantly influences
many consumers’ purchase decisions. The low active and standby power consumption of MHL
transmitters dramatically extend battery life in mobile devices. In the active setting at 720p and 1080i,
typical MHL transmitters consume no more than 40 milliwatts (mW). On standby mode, the
transmitters consume just 30 microamps (µA). These MHL transmitter power draw specifications can be
up to 10 times lower than typical HDMI transmitters.
Why not just use an analog connection
between the dongle and the HDTV?
Component video requires three video connectors plus stereo audio connectors or a multi-channel audio
optical connector, for a total of five to six connectors. This puts a burden on the manufacturer to
integrate a larger dock connector. In some cases, manufacturers have implemented a serial dock
interface for the compressed media and then decode the media using a digital signal processor in the
dock, an expensive solution duplicating the functions in the mobile device. MHL technology solves this
problem with a low-cost, low-pin count interface.
Does MHL technology support CEC?
The Consumer Electronics Control (CEC) Interface block provides CEC compliant signals between CEC
devices and a CEC master. A CEC controller using the Silicon Image CEC Programming Interface (CPI)
is included on-chip. This CEC controller has a high-level register interface, accessible through the I2C
interface, which is used to send and receive CEC commands. This controller makes CEC implementation
very straight forward, removing the burden from the host CPU to manage bit transitions on the CEC
bus. In the MHL application, the CEC/CPI logic is implemented as a distributed solution. The CPI
registers are accessed by the host through the MHL transmitter I2C registers, but the actual CEC
operation occurs in the MHL receiver.
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In Summary, what are the key features of MHL technology?
•
MHL technology provides HD audio/video with only five pins, allowing a tiny connector suitable
for mobile devices;
•
MHL technology conserves battery life with ultra-low active and standby power draw;
•
MHL technology supports digital HD video over a single cable with resolutions up to 1080p;
•
MHL technology is compatible with the HDMI input ports found on most DTVs today;
•
MHL technology includes integrated CEC functions and arbitration logic.
What Silicon Image products are available that support MHL Technology?
MHL Transmitters
MHL transmitters are low pin-count digital media transmitters featuring a single data lane Transition
Minimized Differential Signaling (TMDS) solution, which reduces pin count for small devices. These
transmitters can deliver full high-definition (HD) video and digital audio through five pins on miniature
connectors. MHL Transmitters are available with support for Mobile Industry Processor Interface
(MIPI) input or parallel RGB/YCbCr/ITU.601/ITU.656 digital video input. The low active and standby
power consumption of MHL transmitters extend battery life in mobile devices.
Silicon Image’s MHL transmitters include the VastLane SiI9224, which supports the MIPI input
interface, and the VastLane SiI9226, which supports parallel RGB/YCbCr/ ITU.601/ITU.656 input
interfaces.
FIGURE 2: Silicon Image MHL Transmitter Diagram
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MHL Bridges
MHL-to-HDMI bridges convert an MHL technology enabled device’s audio and video signals into a
standard HDMI signal. The MHL bridge provides a cost-effective solution for a docking station or dongle
that is HDMI compatible. The VastLane SiI9290 MHL bridge is Silicon Image’s HDMI-to-MHL bridge
solution.
FIGURE 3: Silicon Image Typical MHL Bridge Implementation
HDMI Receivers with MHL Support
MHL-ready HDMI receivers allow MHL equipped mobile devices to be connected directly to the DTV
without need for a docking station bridge. Silicon Image’s PinnaClear SiI9223 is a four-port HDMI
receiver that delivers advanced HDMI 1.3 HDTV features including 1080p Deep Color and x.v.Color
expanded color gamut, and includes support for MHL technology.
FIGURE 4: Silicon Image Typical MHL Receiver Implementation
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About Silicon Image, Inc.
Silicon Image, Inc. is a global leader in driving the architecture and semiconductor implementation for
the secure storage, distribution and presentation of high-definition content in the consumer electronics,
personal computing, and mobile device markets. With a rich history of technology innovation that
includes creating industry standards such as SATA, DVI and HDMI, Silicon Image partners with the
world’s leading entertainment creators and electronics manufacturers to deliver digital HD content to
consumers anytime, anywhere, on any device. Silicon Image is also a leading provider of semiconductor
intellectual property solutions for high-definition multimedia and data storage applications.
Additionally, Simplay Labs, LLC, a wholly-owned subsidiary of Silicon Image, offers robust testing tools,
technologies, support services, consulting and product certification to electronics manufacturers to
maximize performance, interoperability and ensure the highest-quality HD experience to consumers.
With engineering, sales and customer support facilities located throughout North America, Asia and
Europe, Silicon Image (NASDAQ: SIMG) is globally headquartered in Sunnyvale, California. For more
information, please visit www.SiliconImage.com.
1060 E. Arques Avenue
Sunnyvale, CA 94085
T 408.616.4000 F 408.830.9530
www.siliconimage.com
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