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Multimedia ICs
NTSC color TV signal encoder
BA7230LS
The BA7230LS comprises an RGB signal matrix circuit, balanced modulator circuit (rectangular 2-phase modula-
tion), oscillator circuit (VCXO) for a 3.58MHz subcarrier synchronized with video input burst signals, luminosity and
color difference signal mixing circuit, and a high speed switch for selecting composite signals of video input and RGB
input. RGB signals, synch signals, BFP (burst flag pulses), PCP (pedestal clamp pulses) are input, and an NTSC
composite signal is output.
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Applications
Televisions (Teletext-capable), captain systems, video cameras, personal computers
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Features
1) Allows superimposition of video images (VIDEO IN)
and computer images (RGB IN).
2) During superimposition, the subcarrier locked onto
the video input burst signal RGB is modulated with
the RGB signals by the APC circuit, preventing
unnatural color disturbance due to switching.
3) Both the RGB and video input signals are pedestal-
clamped, maintaining a natural image even during
fluctuation in luminosity.
4) Using a half down pulse, the video signal can be
reduced by 5dB to darken the background and
make the superimposed RGB image easier to see.
5) Carrier leak is suppressible to less than 70mVP-P
(VOUT = 2VP-P) without adjustment.
6) Can be adapted for analog RGB input.
7) Compact 24-pin SZIP package minimizes external
components.
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Block diagram
1VIDEO OUT
3Y IN
5R-Y IN
7VC
9
APC PHASE
ADJUSTMENT
11
VA
13AR
15AB
17B-Y OUT
19GND
21PCP IN
23YSP IN
2 SYNC IN
BA7230LS
4 B-Y IN
6
PD
8 VB
10
BURST LEVEL
ADJUSTMENT
12
BFP IN
14 AG
16 Y OUT
18 R-Y OUT
20 VIDEO IN
22 HDP IN
24 VCC
VCC
B - Y R - Y
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HD
MATRIX
PD
VCXO
MOD MOD
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