Philips EM7U LCOS, Service Manual

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AV3 AND AV4 INPUTS (Figure 45)
The AV3 and AV4 inputs allow the input of Component Y Pb Pr signals from a 1080I, 480p, or
NTSC source. Better results are obtained by inserting the NTSC Component source into
AV2. Each of the AV3 and AV4 inputs are clamped to limit the level of the signals applied.
This is accomplished by using diode arrays, 6711, 6710, 6712, 6632, 6631, and 6630. The
positive portion of the signal is clamped to 5.6 volts and 0.6 volts in the negative direction.
IC 7710 selects the two AV sources. This is a High Frequency switching IC with minimal
cross talk. Pixelworks IC controls the IC via the 2FHIN1_2FH1N2 line. The Control line is
inverted by Transistor 7725, which is connected to Pin 19. When the Control line is High,
7725 turns On to pull Pin 19 Low. This selects input AV4. When the Control line goes Low,
Pin 19 goes High and AV3 is selected. To reduce interference, each section of the IC is
powered by a different 5-volt supply. The Y Pb Pr signals are output on Pins 30, 27, and 35.
The signals are then buffered by Transistors 7716, 7717, and 7715.
Page 47
AV3, AV4, AND VGA PROCESSING SECTION