Lower costs and ease of mass manufacturing have increased LCD panel 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, PDAs, and other handheld devices. 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.
Using Actel's Display solutions provide a host of key benefits:
- Actel's ultra-low-power flash FPGAs can be used to build customized LCD controllers
- Actel's display solutions accommodate display panels of varying resolutions and from multiple manufacturers
- IGLOO® FPGAs offer 5 µW standby power, are reprogrammable, and
require only 1 µs to enter or exit Flash*Freeze mode, increasing battery life
- Wide selection of reference design blocks and demonstration platforms are readily available
- Network of Solutions Partners are at your service to meet your design needs
LCD Types
Different manufacturing processes create the two major types of LCD panels:
- STN: A super twisted nematic (STN) LCD uses monochrome passive matrix technology to provide color contrast. It is an older technology that is cheaper to manufacture, but typically provides lower image quality and slower response time compared to others.
- TFT: The thin film transistor (TFT) LCD uses active matrix technology to improve image quality. It is the most popular LCD type on the market.
Simple LCD Controller
The figure below shows a simple LCD controller, which consists of an interface to the 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 ultra-low-power IGLOO device can effectively interface with the MCU and the off-chip buffer for image data storage. Since the IGLOO FPGA contains up to 500 kbits of embedded SRAM, it can store display data internally for small displays. Once the controller design is programmed into the IGLOO FPGA, image data can be processed and appropriate video timing signals can be generated for the LCD panel. You can select which blocks go 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 IGLOO FPGA.
Backlight Control
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 CCFL backlight to LED backlight, IGLOO devices can play a crucial role in performing control and leading with a power advantage.
The LED driver chips are equipped with a PWM input signal, which is used to perform brightness control. A PWM block can be implemented in an IGLOO device, as shown in the figure below.
In addition to PWM brightness control, the Flash*Freeze feature of the IGLOO device can be designed to display LCD data and switch off the LED backlight. Flash*Freeze mode is a special feature that puts an IGLOO device in sleep mode, operating at power as low as 5 µW. All I/Os become tristated when enabled, and the device maintains the same state as before the activation. Once Flash*Freeze mode is deactivated, the IGLOO device will instantly jump to an operational state within 1 µs.
Complex LCD Controller
The figure below illustrates a complex LCD controller that can also be implemented within the IGLOO architecture. This type of LCD controller is found in portable media players and automotive dashboard applications, where multiplexing several images and video data is common. In this application, the IGLOO device can perform several complex functions, such as:
- De-interlacing the source video from CMOS sensor into a progressive video that is suitable for LCD
- Color space conversion from YUV or YCrCb to RGB and vice versa
- An On Screen Display (OSD) engine can be added to provide overlay menus for user selections. Another function of this is a startup flash screen.
- The alpha blending feature is used to blend two image sources with each other, creating a fade-in / fade-out effect.
Depending on the resolution of data required for storage, off-chip SDRAM can be used as a temporary data buffer. In addition, flash memory is often used for font mapping or storing preloaded data.
Actel offers the following pre-built reference design blocks that enable you to quickly start your display controller design:
Video Timing Generator
The video timing generator generates the timing signals needed for LCD, such as RGB data, HSYNC, VSYNC, pixel clock, and display enable. This block is customized, based on display resolution and timing parameters needed for the LCD.
Frame Buffer Controller
The frame buffer controller manages the data and commands received from an external source such as DVI or MCU. Depending on the resolution of input data, it can be stored in the on-chip RAM or on an off-chip SDRAM for temporary data storage. The frame buffer controller will take care of pixel-level data synchronization between SDRAM and the IGLOO devices.
Frame Grabber
The frame grabber captures a portion (window) of a video source for display or processing.
Color Conversion
Color conversion transforms color space from YUV or YCbCr source to RGB pixel data and vice versa. The design in IGLOO devices is highly optimized to consume the least amount of on-chip resources, while maintaining a very high performance for LCD applications.
Single-Channel LVDS Transmitter
Using Actel's LVDS I/O capability, the single-channel LVDS transmitter can drive LCD displays over longer wire lengths, as in the in-cab entertainment applications, to a maximum performance of up to 600 Mbps per LVDS pair. It includes serialization and appropriate clock synchronization.
On-Screen Display Engine
On-screen display engine enables users to combine text and graphics to display on the LCD.
Alpha Blending
The alpha blending merges multiple video and image sources, and the merged image can be sent to the LCD display, creating a fade-in / fade-out effect.
Color Management
Color management permits adjustment of brightness, contrast, saturation, and hue.
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 Demo 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.
