Equal distribution
05 May 2009
SDI cable equaliser simplifies design of equipment.
A new PowerWise 3 Gbps (3G) Serial Digital Interface (SDI) cable equaliser (EQ) from National Semiconductor simplifies the design of broadcast video routers, production switchers, distribution amplifiers, editing and conversion equipment. The energy-saving LMH0384 offers the industry’s lowest output alignment jitter across cable lengths allowing hardware designers more headroom for designing within system jitter budgets. Tighter jitter budgets translate to cleaner system design, fewer bit errors and crisper images.
The LMH0384 is the only EQ to guarantee less than 0.3 unit intervals of output jitter from zero to 110 m of Belden 1694A coaxial cable at 2.97 Gbps. It equalises up to 140 m of cable at 3G rates, 200 m at high-definition rates and 400 m at standard-definition rates. The device adaptively adjusts equalisation levels based on cable length to receive incoming signals and provide low-jitter transmission of 1080p high-definition broadcast video at up to 60 frames per second over a single coaxial cable.
National’s LMH0384 supports two modes of operation: pin mode and register mode. In pin mode, the EQ is fully backward compatible with National’s other SDI equalisers. Register mode opens up a suite of advanced features - accessible via the SPI bus - that enable flexibility to change and diagnose product parameters without requiring a board re-spin. These include automatic power down (auto-sleep), cable length indicator, LVDS drivers with programmable offset and amplitude, and programmable input launch amplitude to facilitate operation with external splitters. The LMH0384’s 1.05 V to 1.85 V adjustable output common-mode voltage eliminates the need for level-translation buffers by facilitating direct coupling to most FPGAs and signal conditioning devices.
The EQ offers active sensing features to minimise power consumption and reduce cooling requirements in customer systems. For example, in the event of cable detachment or loss of signal, the LMH0384 enters a power-saving auto sleep mode to reduce power consumption by 85 percent. In active mode, the EQ automatically shifts equalisation stages at shorter cable lengths (less than 140 m) to reduce power consumption by 20 percent. The EQ typically consumes 230 mW of power from a single 3.3 V supply.
The LMH0384 is a part of National’s broadcast video portfolio that enables Society of Motion Picture and Television Engineers (SMPTE) 424M, SMPTE 292M and SMPTE 259M uncompressed serial digital video routing and processing applications. The LMH0384 also fully supports the digital video broadcasting-asynchronous serial interface standard at 270 Mbps for compressed video distribution in head-end equipment.
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