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Zetex chipset manages composite video signals

Posted: 10 Apr 2003 ?? ?Print Version ?Bookmark and Share

Keywords:zetex semiconductors? zxfv4583? zxfv4089? sync signal separator? dc restoration amplifier?

Zetex Semiconductors has announced the availability of a two-chip solution for the management of composite video signals in applications such as CCTV, video capture, mixing, and special effects.

The chipset is comprised of the ZXFV4583 sync separator and the ZXFV4089 dc restoration amplifier, and is pin-compatible with industry-standard alternatives.

Acting as a black level clamp, the ZXFV4089 provides brightness level stability in video systems with wide bandwidth, low distortion, and low power consumption. AC coupled, the composite video signal is subject to dc drift due to the variable content of the intensity information.

Containing a sample and hold (S/H) circuit and a low distortion video amplifier, the ZXFV4089 performs dc restoration of the video signal. From the back porch pulse, the device establishes the black level reference for the following part of the signal containing the intensity information. The output is a video signal permanently clamped to a reference voltage.

Sync signals separation

Configured using three external resistors, the ZXFV4583 separates the vertical, horizontal, and composite synchronization signals from PAL, NTSC, SECAM, and other standard and non-standard composite video signals. The device utilizes an S/H process that determines the half point on the negative edge of the sync pulse to achieve the accurate timing of sync extraction.

An optional on-chip low pass filter can also be employed to alleviate the effects of the color carrier, while interlaced video formats are accommodated by an odd/even logic output. Loss of signal detection, at a level set by one of the external resistors, initiates a logic high output.

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