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SDI equalizer breaks cable length barriers

Posted: 08 Sep 2010 ?? ?Print Version ?Bookmark and Share

Keywords:3G? fiber optic?

National Semiconductor Corp. has announced that it has created a serial digital interface (SDI) cable equalizer that extends the reach of broadcast signals while reducing the required power consumption by 40 percent. The LMH0394, which transmits 3Gb/s (3G) data 200m at 3Gb/s, HD data 220m, and standard definition (SD) 400m, typically requires just 115mW power Cor half that of comparable equalizers. The SDI equalizer could help broadcasters reduce operational costs by eliminating the need to upgrade to fiber solutions for sports events and other longer-reach outdoor installations.

Broadcasters have been using fiber-optic solutions or copper links with multiple distribution amplifiers to extend their video equipment's reach. The LMH0394, however, allows transmission of 3G-SDI using a single 200m link of coax cable. Its automatic power-down mode, which kicks in when an input signal is not detected, reportedly cuts power consumption by 85 percent. The power savings, meanwhile, allow designers to add other functionality such as audio processing and reclocking on video input cards.

National Semiconductor said the LMH0394's typical jitter is less than 0.15 unit intervals (UI) up to 100m, 0.20UI up to 140m and 0.40UI up to 180m at 3G data rates. This also helps save power as input relocking of short-reach links is no longer needed. Also available is a dual-output version called the LMH0395. It consumes just 145mW using a 2.5V supply. The dual outputs are independently programmable for various downstream devices with different input requirements and trace lengths.

Among the other key features of the LMH0394 are: power-efficient low-voltage differential signaling (LVDS) drivers with programmable offset, amplitude and output de-emphasis, support for passive external splitters, and a cable length indicator accurate within 1m. They are all accessible through the SPI programming interface. Backward compatible with National's other SDI equalizers, the LMH0394 is available in a 4mm x 4mm 16-pin LLP package while the LMH0395 is in a 24-pin LLP package.

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