[Design View / Design Solution]
Using LCD Panels For TVs Takes Technology To The Outer Limits
Want to push the envelope? Try designing a 46-in. LCD TV boasting more than 1 billion colors and true cinema-quality picture performance.
DESIGN VIEW is the summary of the complete DESIGN SOLUTION contributed article, which begins on Page 2.
From the early 1990s through the early 2000s, the requirements and needs of the thin-film-transistor LCD industry evolved gradually. But with the quickly growing popularity of LCD TVs, the market now demands an entirely new set of performance requirements, which in turn is stressing current silicon architectures and interfaces to the limit.
The television market is calling for disruptive electronics technology to solve the frequency and distance requirements of the interface, provide greater than 1 billion colors, improve the response time for high-quality motion video, and achieve better color uniformity. Mainstream TV panel sizes span 27 to 32 in. today, and at least four companies have demonstrated LCD panels larger than 46 in.
The article discusses the main elements that must be addressed in LCD-panel electronics to accommodate today's demands. For instance, as panel size grows, signal integrity becomes a problem. Options for improving the "data eye" include improving the quality of the pc-board material, altering the data-transmission scheme, and moving to a point-to-point architecture. All are explained in detail.
Another sticky point is color depth, as well as the impending massive increase in decode logic and column-driver size when switching to 10-bit color. Described are dithering techniques and a change in architecture.
Poor motion-video capability hampers LCDs. However, the overdrive method discussed can overcome the otherwise blurred edges of a moving image. One other challenge for panel electronics concerns color quality. The author feels that the problem will only be truly solved if electronics manufacturers provide independent luminance-to-voltage conversions for each color in a cost-competitive manner.
HIGHLIGHTS:
The Panel-Size Issue
Though today's differential bus architectures excel at delivering the bandwidth needs across a 15- to 19-in. panel, signal integrity becomes a problem as panel size increases.
The Color-Depth Issue
The trend for televisions is a color depth of 1 billion colors (10-bit color), creating an eightfold increase in decode logic and making column-driver die size and cost nearly prohibitive. One suggestion is to change from the traditional R-DAC architecture.
Motion-Video Performance
Numerous companies are working on proprietary solutions for response-time compensation. These would ultimately raise LCD motion-video performance to match or exceed today's high-end TVs.
Color Quality
Solving color-quality problems typically involves the timing controller, which manipulates incoming digital data via data expansion and dithering. However, a programmable voltage-to-luminance function for each pixel color will probably be the way to go.
Sidebar: A History Of LVDS And RSDS Interfaces
This sidebar discusses how the low-voltage differential signaling and reduced-swing differential signaling interfaces improved LCD data flow.
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