Video receiver/equalizer goes the distance
By Joshua Israelsohn -- EDN, June 26, 2003
Remote computer monitoring, security monitoring, and other video-at-a-distance applications can present signal-processing challenges even when connected through controlled-impedance coaxial cable. Though the economies of common twisted-pair cabling, such as the ubiquitous Category 5, are compelling, the suboptimal medium makes image recovery impossible over long runs without proper equalization.
Intersil addresses this problem with the Elantec EL9110 receiver/equalizer, which recovers VGA and NTSC video signals from Category 5 cable as long as 1000 feet (Picture). A 0 to 1V dc-control voltage adjusts a five-pole equalizer to compensate for cable losses at frequencies higher than 1 MHz, extending the length of Category 5 runs to 300, 500, and 1000 feet for 150-, 125-, and 75-MHz channels, respectively. Similarly, a control voltage sets the adjustable-gain receiver over a ±6-dB range, providing the means to recover cable attenuation and trim image contrast.
The EL9110 includes a common-mode recovery amplifier, which taps the input ahead of the first differential stage. This feature allows you to recover, for example, an audio feed encoded as a common-mode component to the differential-mode video signal. The video channel's 60-dB common-mode rejection extends to about 400 kHz, which expands the possible uses for the common-mode channel.
The $6.75 (1000) Elantec EL9110 is available in QSOP-16 packages and operates over the –40 to +85°C industrial-temperature range. It draws 33-mA quiescent current from ±5V supplies.
Intersil, 1-408-935-4300, www.intersil.com.
