3-Channel video reconstruction filters eliminate the need for large-ouput AC-coupling capacitors
Maxim Integrated Products introduces the MAX7438/MAX7439, the world's first integrated 3-channel, standard definition, video reconstruction filters with the blanking-level of the video signal clamped to GND. Each channel combines a lowpass filter with adjustable boost levels and an adjustable gain amplifier capable of driving two standard 150 video loads. The output video signal on each channel is clamped to ground, eliminating the need for large (220µF to 1000µF) AC-coupling capacitors. The typical (0.1µF) input series capacitor is also eliminated since the input is directly coupled. This DC-in, DC-out architecture improves line-time distortion (no tilt). The preprogrammed filter supports NTSC, PAL, and standard definition (SDTV) video signals making the MAX7438/MAX7439 ideal for anti-aliasing and DAC (digital-to-analog converter) smoothing in digital video devices. Devices include cable set-top boxes, satellite set-top boxes, DVD players, camcorders, and personal video recorders (PVRs).
The MAX7438 has a buffer gain of 2V/V while the MAX7439 has a buffer gain of 3V/V. The 3-channel MAX7438/MAX7439 are ideal for RGB (Y Pb Pr) component video signals but also support three composite video signals or Y/C plus CVBS video signals. Each filter channel achieves 60dB of attenuation at 27MHz with less than ±0.25dB of passband ripple from DC to 5.5MHz. High-frequency boost circuitry allows adjustment for sharper image with up to 2dB of gain boost in 0.5dB increments without degradation in the stopband attenuation.
These devices save significant board space and design time while providing increased performance at a cost comparable to the standard discrete L-R-C filter and buffer solutions used today. The MAX7438/MAX7439 are available in a 20-pin QFN package in the extended-industrial (-40°C to +85°C) temperature range. Prices start at $2.20 (1000-up, FOB USA).
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Dan Ore contributes and publishes news editorial to http://www.digital-video-camcorders.com.
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