White Paper

Dual Redundant Display in Bubble Canopy Applications

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w w w. m r c y. c o m WHITE PAPER LCD Panel and Drive Circuitry LCD Panel The display is a color Active Matrix Liquid Crystal Display. The matrix employs a-Si Thin Film Transistor as an active element. It is a transmissive type operating in the normally white mode. It has 21.5-inch diagonally measured active area with Full HD resolution (1920 horizontal x 1080 vertical pixel array). Each pixel is divided into red, green and blue sub-pixels which are arranged in vertical stripes with a pixel pitch of 0.248 mm x 0.248 mm. Gray scale of the sub-pixel is determined with an 8-bit gray signal for each sub-pixel, thus, presenting a palette of more than 16. 7M true colors. It has been designed to apply the video data via dual port LVDS interface. Figure 2 shows the LCD block diagram. Figure 2. LCD Block Diagram LCD Drive Redundancy This architecture provides two independent paths for video data, controls and power to the LCD. Two sets of power supplies that generate 3.3V, VDD, VGH and VGL are continuously monitored by mentoring circuitry for any deviation or loss. The arbitration logic selects the appropriate set to the appropriate LCD drive and gamma control. In addition, there are two sets of LCD drive, Vcom and Gamma generation circuits that are monitored continuously. The arbitration logic selects the appropriate set to be channeled to the LCD via the multiplex logic. The video data are also multiplexed and channeled appropriately. Figure 3 shows block diagram of the LCD drive redundancy. Figure 3. LCD Drive Redundancy Block Diagram Introduction Display redundancy is required in all military platforms. Most of the failures in display systems are due to control electronics, power supplies, and backlights, not the AMLCD itself or its row and column drivers. In this architecture, redundancy is established throughout from the video inputs, power supplies and control circuitry. Canopy reflections are controlled by utilizing films or light pipes. Mercury Systems, through worldwide exclusive relationships with AMLCD manufacturers, has been developing, manufacturing, and delivering high-end custom AMLCD products since 1998. This design is now available for applications where a large COTS or custom AMLCD can be utilized with full drive redundancy for the demanding bubble canopy applications. System Architecture With the significant advances in COTS AMLCDs in terms of maturity, processes, materials, reliability, resolution and performance, these components are becoming a more viable approach to fulfill the requirements for Bubble Canopy Applications. The system architecture of the display head assembly is shown in Figure 1. It consists of dual redundant paths of required DC power, associated control signals and video data for the LCD and similarly for the LED backlight. In the backlight section of this design, there are two independent power supplies, A and B, that provide power to the LED controls and drive circuitry. These two independent paths are multiplexed to provide one set of inputs to the Day/Night LEDs. The control signals to the multiplexer are provided through Arbiter logic that is constantly monitoring any deviation in operating power supplies or logic control signals. This scheme provides two independent paths for signals and power to flow to the LCD and LEDs thereby any failure or deviation in these signals that prevents the display from working properly can be eliminated. Figure 1. System Architecture Block Diagram 1

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