Extending the Cable Reach of HDMI/DVI Solutions
National’s HDMI long reach products enable video professionals and consumers to extend the reach of their digital visual interface (DVI), high-definition multimedia interface (HDMI) or low cost CAT-5 cable connections beyond 100m over the entire range of HDMI v1.3 and DVI 1.1 data rates.
HDMI is the de facto standard for transferring uncompressed all-digital video and audio in the consumer electronics market. By delivering all-digital audio and video via a single cable, HDMI dramatically simplifies cabling and helps provide consumers with the highest-quality home theater experience. HDMI provides an interface between any audio/video source, such as a set-top box, DVD player, or A/V receiver and an audio and/or video monitor, such as a digital television (DTV).
HDMI standards are continually evolving to support demands of HD display devices. The latest version, HDMI v1.3, supports a single-link bandwidth up to 340 MHz (aggregate data rate:10.2 Gbps) to support the demands of future HD display devices, such as higher resolutions (1440p), 16-bit Deep Color and high frame rates (240Hz).
HDMI specifies the required performance of a cable but does not specify a maximum cable length. Most cables pass "Standard Cable" HDMI compliance testing at lengths of up to 5-10 meters without the use of a repeater. These cables work well for short distance applications where the cable losses have little effect. However, many applications such as HD projectors, home theatres, display walls, industrial video, etc. require a longer cable reach. At longer cable lengths, the cables degrade the video signal by introducing attenuation, jitter, skew and crosstalk resulting in unacceptable artifacts such as screen flicker, noise sparkles, and audio distortion at the display end.
- National’s HDMI v1.3a-compliant cable-reach extenders counter many of the negative effects caused by longer cables. These chips have
Cable equalizer that boosts high frequency energy and shapes the signal to compensate for the finite bandwidth effects of the cable such as high frequency attenuation and inter-symbol interference (ISI).
- Clock and data recovery circuit retimes the data with a clean clock recovered from the data stream to remove any residual jitter.
- Output buffers provide adjustable amplitude and de-emphasis to enable transmission over longer length of cable. The devices also support AC coupling of the signal at the transmit end to enable transmission over lower cost CAT5/6 cables.
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