DisplayPort-based displays, where, why and when - Embedded.com

DisplayPort-based displays, where, why and when


DisplayPort, the new standard being promoted by VESA as the next-generation digital interface between high-resolution displays and display sources, has already seen wide adoption by PC graphics vendors (such as Intel, NVIDIA and ATI). However, DisplayPort will not only be applied in the desktop display markets, but also in notebooks, TVs and even projectors. All of these markets can benefit from DisplayPort for different reasons and at different time frames. This paper breaks down the different applications and explores the reasons why and when each will adopt this new standard.

Notebooks traditionally use Low-Voltage Differential Signal (LVDS) as the interface between the graphics chip and the LCD panel. If you peek in the hinge area of a notebook, sometimes you can see this bronze-colored ribbon connector carrying the LVDS display signals from the base of the notebook to the lid where the LCD resides. With DisplayPort, EMI and routing skew concerns are greatly reduced. This is because DisplayPort uses SerDes technology with an embedded clock. This technology allows the receiving end to receive data almost asynchronously between lanes, and simply re-time the data itself by extracting the embedded clock. Having said that, the main reason notebook computers would replace LVDS with DisplayPort is for power savings. With high-speed DisplayPort, the entire system chipset where the graphics reside can be simplified, and much of the traditional digital-to-analog conversions required for the traditional VGA connection can be avoided. Overall, the power of the graphics sub-system can be reduced by as much as 20 percent, according to Intel. That can translate to longer battery life of up to 20 minutes. Overall, with DisplayPort's reduced EMI issues , less special EMI treatment is needed, all adding up to overall cost savings.

On the external monitor interface front, DisplayPort is also replacing the traditional VGA connector (DB-15). Not only does this get rid of the D/A converters necessary to generate the analog VGA signals, it also replaces the physically large DB-15 connector with a much smaller and thinner DisplayPort connector. This then allows form-factor innovations to occur, such as the revolutionary thinness of the Apple Mac Air. If the VGA connectors are still used, the connector would limit the thickness of the entire notebook computer.

Other than the Apple Mac Air, HP, Dell, Lenovo and other OEMs are all shipping notebooks with DisplayPort. This was driven by the availability of the Montevena chipset from Intel, which included standard DisplayPort. The next-generation chipset, Capella, will take further advantage of power savings and integration by optimizing for the all digital output of DisplayPort. , so we'll expect an acceleration of DisplayPort adoption with these new platforms.

Desktop Monitors
With desktop monitors, the main reason to switch to DisplayPort is cost. By leveraging DisplayPort's high-bandwidth capabilities, much of the display scaling functions can now be shifted to the GPU in the system. Now that there is enough bandwidth, the GPU can pre-scale the image while taking advantage of source data availability, and then transmit the fully up-scaled image to the monitor for display at full resolution. This is compared to today's solution of a separate scaler IC in the monitor that scales the image to the native resolution of the LCD panel. With the monitor scaler IC removed, “Direct Drive” monitors can be realized, and the overall cost of the monitor reduced. In addition, with the GPU fully in control of the actual display resolution, it's now much easier to manage multi-monitor configuration as the GPU now knows exactly what resolution, and thus frame buffers it needs to manage. With DisplayPort's built-in capability of daisy chaining, it's now much easier to have multiple monitors on your desktop and have the GPU mange how your application can span across them. With IDT's recent announcement of ViewXpand, it is a great example of this capability. The ViewXpand product allows a single DisplayPort output from a desktop or notebook computer to be expanded to drive up to three monitors for a panoramic view, all without any changes in PC hardware or software. In applications where you are just driving one single monitor, these scaler-less monitors are less expensive, but higher performing “Direct Drive” monitors, and are likely to be first offered by OEMs as bundled monitors with a system. However, we do see DisplayPort already being offered by retail monitor manufacturers as an option. In the retail markets, where matching up monitors and systems are not as predictable, retail monitors will continue to offer legacy interfaces (DVI, VGA) in addition to DisplayPort.

TVs and Projectors
In TVs and projectors, the motivation to add DisplayPort as an input interface will simply be to offer additional connectivity options as computers adopt it as an output interface. DisplayPort has a lot of advantages over traditional VGA or DVI interfaces, with longer cable drive capabilities and reduced pin counts translating to less wires, thus lowering cable cost. In consumer applications where legacy support is important (just look at the back of your HDTV, they still carry composite video inputs), DisplayPort adoption will not likely “replace” any standards, such as HDMI, in the short term. However, DisplayPort will simply be an added input option.

However, if one looks “inside” a TV, there are definite DisplayPort adoption possibilities with internal interconnects such as those between the TV tuner board and the mail processor boards. Also they can be used between the panel itself and the processor boards. With large screen TVs reaching 64″ and up, the interconnect distance between processing boards inside the TV can reach a few feet. DisplayPort again offers EMI, cost, performance and power advantages over existing interface standards, such as LVDS and others. These embedded applications “inside” a TV may exceed external applications in the near future because there are often more interconnects “inside” a TV as compared to outside a TV.

DisplayPort, the new high-performance digital VESA display interface, helps eliminate many shortfalls of existing display interfaces as resolutions continue to climb. Market analysts are still reporting that analog CRTs still represent approximately 40 percent of worldwide TV sales in 2009. Thus, with the continued transition to digital, flat panel displays will greatly benefit from a high performing, yet low cost interface. In addition to TVs, we will see the adoption of DisplayPort in many markets and applications. Most of these will be adopted for different reasons, and at different time frames. Moreover, many of these applications are embedded, so you may already own a piece of equipment with DisplayPort and not even know it.

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