UPC1830GT NEC, UPC1830GT Datasheet - Page 14

• Manufacturer Part Number: UPC1830GT
• Description: FILTER-CONTAINING VIDEO CHROMA/ SYNCHRONIZING SIGNAL PROCESSING LSI COMPATIBLE WITH NTSC/PAL SYSTEM
• Manufacturer: NEC

5.2 Chroma Signal Processing Section
(1) Input signal
(2) Chroma BPF circuit
(3) Separate/composite switching circuit
(4) ACC (Auto Color Control) amplification circuit
14
• Composite video signal input
• Separate chroma signal input
Separates the chroma signal from a composite video signal.
When the potential of the separate chroma input pin (pin 34) is 3.7 V or higher (in composite mode), switches the ACC
amp input from the chroma input pin to the chroma BPF circuit output. Processing of the brightness signal at this time
is switched so that it passes through the chroma trap circuit.
Operation when switching separate/composite signals is shown in Table 5-1.
Extracts the burst signal, detects its level and smoothes the voltage of the ACC filter pin (pin 32) by an external
capacitor.
This smoothed voltage controls color gain to keep the amplitude of the burst signal constant.
After coupling by a capacitor (0.22 F), a 1 V
input pin (pin 36).
After coupling by a capacitor (1000 pF), a chroma signal whose burst signal amplitude is 150 mV
to the separate chroma input pin (pin 34).
2
1
0
400 mV
(a) NTSC mode
1
Contrast control pin voltage (V)
p-p
stair step (composite) input
2
Figure 5-1. Contrast Control Characteristic
3
V
CC
4
= 5 V
5
p-p
composite video signal is input to the composite video signal
2
1
0
400 mV
1
Contrast control pin voltage (V)
p-p
stair step (composite) input
(b) PAL mode
2
3
V
CC
4
= 5 V
p-p
is input
5
PC1830