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High Speed RGB to YPBPR Converter

 

An LT6559 and an LT1395 can also be used to map RGB signals into YPBPR “component” video. The LT1395 performs a weighted inverting addition of all three inputs. The LT1395 output includes an amplification of the R input by –324/1.07k = –0.3. The amplification of the G input is by –324/549 = –0.59. Finally, the B input is amplified by 324/2.94k = – 0.11. Therefore the LT1395 output is –0.3R, –0.59G, –0.11B = –Y. This output is further scaled and inverted by –301/150 = –2 by LT6559 section A2, thus producing 2Y. With the division by two that occurs due to the termination resistors, the desired Y signal is generated at the load. The LT6559 section A1 provides a gain of 2 for the R signal, and performs a subtraction of 2Y from the section A2 output. The output resistor divider provides a scaling factor of 0.71 and forms the 75Ω back-termination resistance. Thus the signal seen at the terminated load is the desired 0.71(R – Y) = PR. The LT6559 section A3 provides a gain of 2 for the B signal, and also performs a subtraction of 2Y from the section A2 output. The output resistor divider provides a scaling factor of 0.57 and forms the 75Ω back-termination resistance. Thus the signal seen at the terminated load is the desired 0.57(B – Y) = PB. As with the previous circuit, to develop a normal sync on the Y signal, a normal sync must be inserted on each of the R, G, and B inputs or injected directly at the Y output with controlled current pulses.