eDP: A better embedded display ecosystem

May 02, 2016

Craig Wiley-May 02, 2016

Today’s personal electronic devices continue to get smaller and easier to use, with more performance and functionality. Such advances are often driven by technology hidden from the consumer, behind the sleek industrial design and elegant user interface. Video quality improvements are one example. A “better” display is normally equated to more pixels per inch driven by a multi-core GPU that supports high-resolution rendering. But “better” can also be one that uses less power to extend battery life, interferes less with wireless service to enable better coverage, and improves chip integration to enable sleeker, lighter-weight system designs.

These are the types of refinements addressed by the latest revision to the VESA (Video Electronics Standards Association) Embedded DisplayPort Standard. Embedded DisplayPort, commonly known as eDP, is based on the VESA DisplayPort Standard. DisplayPort is the high-performance external audio/visual (A/V) interface developed and deployed by the personal computer industry through collaboration within VESA, providing display resolutions of 4K and beyond. DisplayPort itself continues to gain momentum and is now moving onto tablets and phones as a supporting feature of the new USB-C connector in the form of “DisplayPort Alt Mode.” Like DisplayPort, eDP also offers display resolutions beyond 4K. Designed to replace the internal LVDS display interface developed in the mid 1990s, eDP is used in virtually all new computers with an internal display, including laptops, all-in-ones, and many high-end, higher-resolution tablets.

The development of both DisplayPort and eDP was driven by a variety of computing needs. Foremost among these was hardware integration. As process geometries continued to shrink, a new lower-voltage AC-coupled interface was needed to continue integrating the high-speed display interface into the GPU or system chip. This is because the DC-coupled, high-voltage swing interfaces in use today?including LVDS, DVI, and HDMI?require either the use of external interface chips or process changes that compromise performance. Running at a much higher bit rate, eDP also reduces the number of wires in the interface as well as the number of pins for the interface (Figure 1). The higher bit rate also enables higher resolution, color depth and frame rate. eDP also includes unique features to better manage system power for longer battery life, and lower EMI and RFI thereby reducing the need for heavy and bulky shielding. 

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Figure 1: At display resolutions beyond Full HD (1920x1080) or Full HD+ (1920x1200), eDP has a significant advantage over LVDS in minimizing the number of high-speed wire pairs needed in the display interface, which in turn results in reduced total system footprint. (Source: VESA)

VESA recently announced an update to the eDP Standard. Called eDP v1.4b, this new version puts the finishing touches on the eDP v1.4 Standard that was released in February 2013. Panels capable of supporting eDP v1.4b are now in production, and eDP v1.4b will be enabled in 2016 notebooks. eDP v1.4b includes several enhancements to enable improved flexibility of system implementation, reduced device complexity and lower bill of materials (BOM) costs. However, before we get into what’s new for eDP v1.4b, let’s look back at why the eDP Standard was first developed, and how it has affected the electronics ecosystem through the collaborative efforts of VESA member companies that continually evolve this standard and propagate it across the supply chain.

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