Multimedia ICs
NTSC color TV signal encoder
BA7230LS
The BA7230LS comprises an RGB signal matrix circuit, balanced modulator circuit (rectangular 2-phase modulation), 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.
•Applications
Televisions (Teletext-capable), captain systems, video cameras, personal computers
•Featuressuperimposition of video images (VIDEO IN)
1) Allows
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.
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 pedestalclamped, maintaining a natural image even during
fluctuation in luminosity.
•Block diagram
BA7230LS
VIDEO OUT
1
Y IN
3
R-Y IN
5
VC
7
VA
9
2
4
B-Y IN
6
BURST LEVEL
ADJUSTMENT
8
+
SYNC IN
VB
+
MOD
MOD
VCXO
10 BFP IN
APC PHASE
11
ADJUSTMENT
PD
12 PD
AR 13
14 AG
AB 15
16 Y OUT
MATRIX
B-Y OUT 17
B-Y
18 R-Y OUT
R-Y
GND 19
20 VIDEO IN
HD
PCP IN 21
22 HDP IN
YSP IN 23
VCC
24 VCC
1
