Electronic Design

ICs Better Video Distribution Over CAT-5 Cabling

Differential receiver/equalizer compensates 1000 feet of UTP while high-speed differential line drivers and receivers include the first triple-channel amplifiers.

The EL9110 differential receiver/equalizer from the Elantec division of Intersil integrates several functions needed to distribute video over low-cost CAT-5 unshielded twisted-pair (UTP) cables. In doing so, it offers a compact, low-cost alternative to discrete receive-side solutions.

The chip replaces a differential input buffer, a 0- to 40-dB VGA, a fixed 20-dB gain block, a differential-ended to single-ended converter, an equalizer, and a common-mode recovery amplifier. The equalizer is a five-pole filter that compensates for the frequency response of CAT-5 cable. The amplifiers correct for as much as 60 dB of loss at 75 MHz, which occurs over a 1000-ft run of cable.

Above 100 MHz, system gain is rolled off to reduce noise bandwidth. For a signal bandwidth of 125 MHz, the chip will compensate for 500 feet of CAT-5 cable. Gain may be adjusted ±6 dB via a control voltage to compensate for different lengths of cable. The filter's transfer function is set to compensate for the average response of CAT-5 cable, which is derived from measurements taken on a population of cables.

Also, the EL9110 includes a 150-MHz 3-dB bandwidth, tristatable output, ±-5-V supply operation, and a 33-mA no-load supply current. When external passives are counted, the EL9110 occupies a space just a little larger than the chip, a 16-pin QSOP with a 0.193- by 0.236-in. footprint. In contrast, a discrete implementation may require 9 in.2 of board space. And, the Intersil differential receiver/equalizer costs $6.75 in 1000-piece quantities versus nearly $10 for a discrete implementation.

The company has introduced a family of differential line drivers and receivers for video and DSL applications over CAT-5 cable as well. Elantec's EL5X7X family features single and triple op amps with 200- and 500-MHz bandwidths. The availability of triple differential drivers and receivers simplifies gain matching compared to that currently required with single-channel amplifiers.

Two notable examples in this family, the EL5374 triple driver and EL5375 triple receiver, feature 500-MHz bandwidths and about 10 mA/channel of current consumption from single 5-V or dual ±-5-V supplies. In contrast, comparable single-channel devices on the market draw closer to 50 mA.

Thousand-piece pricing for the EL5374/75 is $3.99 per unit. Members of the EL5X7X family are sampling now, with production expected in the third quarter.

Intersil Corp.
www.intersil.com/design/elantec/opAmps.asp

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