Reference Design
There is a reference design that implements the concepts of this article. Figure 5 shows the LMH6733 CFB, which is used to implement the video transmit circuitry. The RCA connectors provide input source connection for an HD 1080i video signal. Video transmission through the CAT5 cable is connected with a RJ45 connector.
Figure 5: CAT5 Video Transmitter Board
Figure 6 shows the implementation of the LMH6733 CFB for both the video receiver and equalizer. The RC equalization network is shown at the bottom of the reference board. An RJ45 connector connects the CAT5 cable to the board while the RCA connectors provide connection for displaying the transmitted video.
Figure 6: CAT5 Video Receiver & Equalization Board
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Both reference boards are equipped with an LM2734 buck-boost regulator to generate a negative 5V from a positive 5V power supply. This alleviates the end user’s need for two power supplies.
This article has shown that a low-cost solution is feasible to transmit HD 1080i component video using one of National Semiconductor’s high speed CFB amplifiers to implement all three video circuit sections. Furthermore, a simple equalization RC network can be used to compensate for attenuation of CAT5 cable up to 500ft. Refer to application note AN-1822 (http://www.national.com/an/AN/AN-1822.pdf) for further details.
About the Author
Vannavong Philavanh is a staff applications engineer with National Semiconductor’s High-Speed Product Division, based in Ft. Collins, Colorado. He received his BSEE degree from Iowa State University. He can be reached at Vannavong.Philavanh@nsc.com.
