Display Solutions

Lower costs and ease of mass manufacturing have increased liquid crystal display (LCD) usage in various markets. In particular, the handheld market has seen a surge in LCD usage as a result of the increased popularity of personal media players, digital cameras, personal digital assistants (PDAs), and other handheld devices. LCDs are also widely used in medical devices, automotive applications, and industrial and military equipment. When creating devices that meet ever-increasing consumer demands and needs, designers must choose LCD panels that are the right size for their application, have the best resolution, and offer the greatest color depth. After the design process begins, designers often face an even greater obstacle—newer displays with better capabilities and lower cost are launched. As a result, the designer must begin another long, excruciating cycle of panel selection, display controller configuration, and system redesign. Actel's flash line of ultra-low-power, reprogrammable FPGAs provides solutions to address these challenges.

Actel's Display solutions provide a host of key benefits:

• Flexible LCD controller with customized functions
• Wide selection of functions available, such as color space conversion, scaling, alpha blending, on-screen display (OSD), frame buffer controller, and video timing generator
• Interface to various processors, memory components, and displays
• Drive different display panels regardless of interface, resolution, and manufacturer
• Industry–only, panel-swappable display demo platform readily available (IGLOO Video Demo Kit)
• Reference designs with source RTL code free of charge

The functions of an LCD controller are endless and can range from a simple function as driving the timing control signals to the display, or as complex as interfacing with a processor to offload display control functions, such as image rotation, color conversion, image scaling, and video overlays. Actel FPGAs can be use to customized LCD controllers to differentiate it from typical LCD control chips in the market because they offer flexibility and a unique solution for your system. For power-conscious applications, such as mobile phones and portable media devices, Actel's ultra-low-power IGLOO FPGA is best suited. Actel's mixed-signal FPGAs can be used to support both touch screen and LCD control for display systems.

Simple LCD Controller

The figure below shows a simple LCD controller, which consists of an interface to the central processing unit (CPU), a frame buffer controller, and a video timing generator. In this example, the processor is responsible for generating the data and commands for the LCD controller to display. The Actel FPGA can effectively interface with the MCU and the off-chip buffer for image data storage Once the controller design is programmed into the FPGA, image data can be processed and appropriate video timing signals can be generated for the LCD panel. You can select which blocks to place in the FPGA, and you also have the choice to interface with any external processor and memory. The interfaces and controllers can be easily programmed into the FPGA.

Complex LCD Controller

The figure below illustrates a complex LCD controller that can also be implemented with Actel's FPGAs. This type of LCD controller is found in many applications, such as portable media players and automotive dashboard applications, where multiplexing several images and video data is common. In this application, the FPGA can perform several complex functions:

1. De-interlacing the source video from a complementary metal–oxide–semiconductor (CMOS) sensor into a progressive video
2. Color space conversion from YUV or YCrCb to RGB and vice versa
3. An OSD engine can be added to provide overlay menus for user selections. The OSD engine can also be used as a startup flash screen.
4. The alpha blending feature is used to blend two image sources, creating a fade-in/fade-out effect.

Depending on the resolution of data required for temporary storage, off-chip SDRAM is typically used as the frame buffer. In addition, flash memory is often used for font mapping or storing preloaded data. Actel's display solutions reference designs include source code for an efficient frame buffer controller that provides nearly 100% memory bandwidth.

Backlight Control

The LCD backlight consumes the most power in portable applications. Reducing the backlight power is the key to prolonging battery life. With the industry migrating from traditional cold cathode fluorescent lamp (CCFL) backlight to light-emitting diode (LED) backlight, the industry's lowest-power FPGAs, Actel IGLOO, can play a crucial role in performing control and leading with a power advantage.

The LED driver chips are equipped with a pulse-width modulation (PWM) input signal, which is used to perform brightness control. A PWM block can be implemented in an IGLOO FPGA, as shown in the figure below.

In addition to PWM brightness control, the Flash*Freeze feature of the IGLOO FPGA can be designed to display LCD data and switch off the LED backlight. Flash*Freeze mode is a special feature that puts IGLOO FPGAs in a low-power mode, operating at power as low as 2 µW. All I/Os become tri-stated when enabled, and the device maintains the same state as before the activation. Once Flash*Freeze mode is deactivated, the IGLOO FPGA will instantly jump to an operational state within 1 µs.

The IGLOO Video Demo Kit offers you the ability to evaluate various display controller reference design blocks for your display system needs. It consists of a set of two boards: (1) The Video Board and (2) LCD Adapter Board. You can choose different LCD adapter boards with LCD panels of different sizes and resolutions to jump-start your development. » Buy a kit from Avnet

Actel offers several LCD control reference designs free of charge to Actel customers. These display reference designs are functional with the IGLOO Video Demo Kit and showcase the flexibility of Actel's FPGAs in performing various LCD control functions, such as digital camera display or digital photo viewer. IP blocks used in the reference designs include Video Timing Generator, Frame Buffer Controller, and more. » Read more about the reference designs

The IP used in these reference designs is available free of charge in source code. See the Display Reference Design page for instructions. For any other display-related IP from our partners, see the Video and Dispaly IP modules.

Actel has partnered with Attodyne, a leader in video and FPGA design services, to provide support and design services for the customized LCD adapter board and other video related services.