Consumer electronics (games & toys): integrated video filter drivers score big with gamers.
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This article will examine how integrated video filter drivers enable portable electronic games to achieve high-definition quality video performance, integrate the capability of driving larger displays, and yet maintain their popular, compact size.
The Handheld Market Comes Into Play
Handheld gaming devices are an emerging market for integrated video filter driver accessory ICs. An integrated video filter driver provides reconstruction filtering that eliminates undesired noise on a video signal. The filtering capability is coupled with an output driver that is capable of driving video off the portable gaming device; ultimately allowing the consumer to view the game on a larger monitor and share the gaming experience with others. Many integrated video filter drivers on the market provide much-needed electrostatic discharge (ESD) protection, helping to protect the handheld from electrical stress that may be introduced via the external cable.
More and more consumers now want the capability of watching movies on their gaming units. Tiny, low power integrated video filters enable portable units to display standard definition (SD) or high definition (HD) video on larger monitors. As the quality level of the video increases, the effect of noise becomes more visible. This increases the need for video filtering.
When consumers connect their handheld gaming device to a larger display, they want to view a crisp, clean video signal. The SOC drives the unit's display, but it does not have the capability to filter and drive video off the handheld device. The SOC handles the digital processing of the video signal, and it also converts this signal back into the analog domain with a digital-to-analog converter (DAC); this process is called reconstruction.
The analog video signal can then be used to drive an external display. High frequency artifacts are introduced during the reconstruction process, which distorts picture quality. A reconstruction filter removes these artifacts through low pass filtering. The filter's reconstruction performance is based on how well the artifacts are removed without distorting the video signal within the passband. Noise from the digital-to-analog conversion process causes many adverse affects on a video signal, such as Moire, herring bone patterns and flashing streaks. All of these affects can be categorized as "fuzzy" or "noisy" video.
Defeating Unwanted Video Signals
An output reconstruction (or image rejection) filter removes the clock and sideband components that are present after the sampling and analog reconstruction process (Figure 1). The video signal is between zero and 5 MHz; the Nyquist limit is at one-half the clock frequency; and the lower/upper sidebands or images are centered around the clock frequency. As the figure illustrates, the reconstruction filter removes much of the unwanted signal while passing the desired video signal.
Today's consumers are also continuously looking for more compact units with more mobile play time, making the main requirements for video filter drivers size and power consumption. Fairchild's FMS6151 meets these requirements with its 1.45 mm X 1 mm X 0.55 mm package and combination of the reconstruction filter function with a fixed gain of 6 dB video drive capability and 6 kV of ESD protection.
For consumers who want to display HD quality video on a larger television, a high-definition filter is required. A high-definition YPbPr video signal uses three channels. As shown in Figure 2, a typical third-order discrete LC filter requires four components: 12 components for three channels. Additional components are required to add drive or gain capability, bringing the component count to above 25. In addition to the space consumed by this discrete approach to filtering, the wide tolerances of passive components cause frequency variations in the filter response. For consistent video performance, filter frequency adjustment or tweaking is required when using discrete components. This time-consuming task is eliminated when using an integrated device.
The integration into one silicon chip lowers part count, decreases board space and improves filter reliability. Integrated video filter drivers offer <[+ or -]10 percent variation in frequency response--a sharp contrast to the standard [+ or -]20 percent tolerance on discrete capacitor and inductor components. If left unscreened, the discrete LC filter can have frequency variations of over [+ or -]20 percent. LC filter performance varies over time, whereas an integrated filter offers a consistent filter frequency that does not change over time.
The trend for consumer electronic video games to get smaller and smaller, while providing more and more functions and features, is not likely to end soon. For example, many handheld gaming units are now providing PDA functions. To keep up with this consumer trend, there will be a continued demand for semiconductor ICs to provide high-performance features. The video-filter-driving semiconductor accessory ICs on the market today offer designers low-power, compact and cost-effective options that enable the portable video games of today and tomorrow.
Debbie Brandenburg is marketing engineer, Signal Conditioning Products, for Fairchild Semiconductor. Before joining Fairchild, Debbie was marketing/applications engineer at KOTA Microcircuits. She has also been an applications engineer at both National Semiconductor and Comlinear Corporation. Debbie has a BSEE from Colorado State University. For more information, contact Fairchild Semiconductor, 82 Running Hill Rd., Portland, ME 04106; (800) 341-0392; www.fairchildsemi.com.
By Debbie Brandenburg, Fairchild Semiconductor
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|Title Annotation:||INDUSTRY FOCUS|
|Publication:||ECN-Electronic Component News|
|Date:||Nov 1, 2006|
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