ROHM BA7230

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
•1)Features
Allows superimposition of video images (VIDEO IN)
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
SYNC IN
4
B-Y IN
6
BURST LEVEL
ADJUSTMENT
8
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
Multimedia ICs
BA7230LS
2
1
CLAMP
5
1kΩ
9.1kΩ
500Ω
2V
5.6kΩ
VCC
22
10kΩ
15kΩ
GND
7
3.4V
10
16
5.1kΩ
1kΩ
10kΩ
15kΩ
5kΩ
17
11kΩ
6.8kΩ
9
18
1kΩ
1kΩ
5.1kΩ
1.2kΩ
4.3kΩ
10kΩ
VCC
6.8kΩ
2.7V
11
12
13
14
15
Fig. 1
•Absolute maximum ratings (Ta = 25°C)
Symbol
Limits
Unit
Power supply voltage
VCC
7.0
V
Power dissipation
Pd
500∗
mW
Operating temperature
Topr
– 20 ~ + 70
°C
Storage temperature
Tstg
– 55 ~ + 125
°C
∗ Reduced by 5.0mW for each increase in Ta of 1°C over 25°C.
•Recommended operating conditions
Parameter
Symbol
Limits
Unit
VCC
4.5 ~ 5.5
V
R input level
VR
0 ~ 0.7
VP-P
G input level
VG
0 ~ 0.7
VP-P
B input level
VB
0 ~ 0.7
VP-P
Video input level
VIN
0 ~ 1.0
VP-P
Power supply voltage
2
19
10kΩ
BA7230LS
1V
Parameter
20
500Ω
6
8
21
10kΩ
CLAMP
2V
1kΩ
4
23
2.2V
10kΩ 15kΩ
3.2V
24
15kΩ
3
15kΩ 7.5kΩ
•Input / output circuits
Multimedia ICs
BA7230LS
•Electrical characteristics (unless otherwise noted, Ta = 25°C, V
CC
Parameter
Quiescent current
= 5.0V)
Symbol
Min.
Typ.
Max.
Unit
Conditions
IQ
—
38
54
mA
—
2.6
VP-P
Video output level
VOV
Half down level change
GVH
–3
DC offset
VOF
—
50
160
Crosstalk
CT
—
– 46
– 40
ER-EY output level
VR-Y
0.3
0.42
0.55
VP-P
VR = 0.7VP-P
EB-EY output level
VB-Y
0.2
0.31
0.42
VP-P
VB = 0.7VP-P
YOUT output level
VY
1.0
1.4
1.8
VP-P
VR = VG = VB = 0.7VP-P
Ys switching delay time
TD
—
60
—
ns
SYNC output level
VOS
0.4
0.65
0.9
VP-P
Burst output level
VOB
0.25
0.46
0.8
VP-P
RE = 1.8kΩ
Composite output level
VOY
1.7
2.2
2.6
VP-P
YIN = 0.7VP-P
1.7
2.2
–5
–7
VIDEO IN = 1VP-P
dB
—
mVP-P
VIDEO IN = 1VP-P
dB
VIDEO IN = 1VP-P
—
—
R-Y modulation gain
GR-Y
9
11
13
dB
R - YIN = 0.3VP-P
B-Y modulation gain
GB-Y
9
11
13
dB
B - YIN = 0.2VP-P
(R-Y) / (B-Y) modulation gain differential
GR-B
—
—
2
dB
(R-Y) / (B-Y) orthogonal phase shift
∆R
–6
—
6
deg
Difference between above gains
—
(R - Y) ·Burst orthogonal phase shift
∆B
–6
—
6
deg
Carrier leak
LSC
—
30
70
mVP-P
APC capture range
fCAP
± 100
—
—
Hz
Burst = 0.1VP-P, 2.8µS
Carrier phase range
φSC
± 30
± 45
—
deg
Superimposition
– 3dB when f = 100kHz
Video frequency characteristic
—
VOUT = 2VP-P
fV
4.5
—
MHz
Video output DG
DG
—
± 3.5
—
%
VIDEO IN = 1VP-P
Video output DP
DP
—
± 2.5
—
deg
VIDEO IN = 1VP-P
Input impedance (SY, BF, PC, HD)
ZT
8
15
—
kΩ
—
Input impedance (Ys)
ZTY
3
7.5
—
kΩ
—
Threshold level (SY, BF, PC, HD)
VT
0.9
2.0
2.8
V
—
Threshold level (Ys)
VTY
0.5
1.1
1.8
V
—
6
3
Multimedia ICs
BA7230LS
•Measurement circuit
VCC
0.7VP-P
~
S1
S2
1µF
S3
1µF
10µF
S4
SYNC
+
ICC
0.047µF
1µF
+
+
+
13
14
15
24
2
CLAMP
19
6dB
MATRIX
v
16
v
~
~
18 R - Y
1kΩ
1kΩ
+4
+5
BA7230LS
B-Y
R-Y
MOD
+1µF
MOD
+
+
6
S5
a
v
~
EB - E Y
ER - EY
17 B - Y
1µF
1µF
75Ω
75Ω
YOUT
Y
YIN
b
3
23
YS
1.8kΩ
PCP
21
6dB
VIDEO
1µF
+ 20
S6
12
BG
PD
BG
VCXO
1VP-P
2.7kΩ
HDP
68pF
TC
7
0.047µF
+
VCC
1
470Ω
9 8
560Ω
82pF
X'TAL
10kΩ
22
BFP
1µF
1.2kΩ
10
Oscilloscope
Fig. 2
4
10k
11
– 5dB
75Ω
Vector scope
820Ω
75Ω
Multimedia ICs
BA7230LS
C1
1µF
C17
0.047µF
B
R2
560Ω
C15
G
R1
20pF
C14
33pF
R
R17 1kΩ
R3
560Ω
LPF
1.2mH L2
560Ω
•Application example
+
+
+
13
14
15
C16
+ 10µF
SYNC
VCC (5V)
24
2
19 GND
20pF
C12
33pF
C13
1.2 mH L1 R16 1kΩ
CLAMP
6dB
MATRIX
YOUT 16
Y
R4
Q1
ER - E Y
2SC2021
EB - E Y
17
VR2
3kΩ
2SC2021
3kΩ
+4
+5
1kΩ
1µF
C4
1µF
MOD
MOD
R5 Video
YS
+
R6
300Ω
YIN
Y
3
R7
1kΩ
5kΩ
23
VR4
VCC
21
6dB
11 VR1
– 5dB
VIDEO IN 1µF
20
PD
R12
2.7k
BG
22
9
– 5dB
0dB
R14
560Ω
68pF
C8
DL1 , DL2 : X503 (SUMIDA)
8
TC1
R13
X'TAL1
C61µ
COMPOSITE
1.2kΩ OUT
R6
82pF
C7 (2VP-P)
C19
10pF
0.047µF
C5
+
C15
0.047µF
7
470Ω
HDP
VCXO
R9
R15 10
1kΩ
APS
PHASE
ADJ
12
BG
C9
10kΩ
BFP
+
DL 2
B-Y
+
+
6
PCP
1kΩ
DLY
R-Y
Burst
LEVEL
ADJ
RGB
BA7230LS
10kΩ
Q2
VR3
TRP
(3.58M)
1µF
C11
300Ω
C10
VCC
DL1
DLY
(400ns)
18
VCC
1kΩ
R11
75Ω
VCC
OUT
820Ω
R10
Q3 2SC2021
L1 , L2 : RC-875 1.2mH (SUMIDA)
TC1 : TZ03R200E (MURATA)
Q1 , Q2 , Q3 : 2SC2021 (ROHM)
XTAL1 : HC – 43U 3579.545kHz (NIKKO DENSHI)
Fig. 3
5
Multimedia ICs
BA7230LS
operation
•(1)Circuit
Matrix circuit
The R, G and B inputs are clamped to 3.2V by the
clamp circuit and combined into signals EY, ER-EY and
EB-EY by the resistance-adding matrix circuit.
EY = 0.30ER + 0.59EG + 0.11EB
ER – EY = 0.70ER – 0.59EG – 0.11EB
EB – EY = – 0.30ER – 0.59EG + 0.89EB
Signal EY is then amplified by the 6dB amplifier (pin 16) to
compensate for the signal's 6dB attenuation in the delay
line. To prevent overmodulation, signal ER-EY is output at
1 / 1.14 and signal EB-EY at 1 / 2.03 (pins 17 and 18).
BA7230LS
The carrier color signal is mixed with color burst signals
and luminosity signals EY' (to which a horizontal synchronization signal is added) to create the NTSC composite signal (EN).
ER – EY
EN = EY' +
cos2πfst
1.14
EB – EY
+
sin2πfst
2.03
(3) Switch circuit
Signal Ys (pin 23) switches between video input and
RGB composite signals. Performing this switching at
high speeds results in superimposition.
27kΩ
RGB
COMPOSITE
5.1kΩ
Y
YS
10kΩ
OUT
13
14
R
15
G
VIDEO IN
B
Fig. 4
Fig. 6
(2) Balanced modulator circuit
Color difference signals are modulated (rectangular 2phase balanced modulation) with color subcarriers
(3.58MHz) having a 90° phase difference. This is
called the carrier color signal.
(4) Color subcarrier oscillator circuit
The subcarrier oscillator circuit for RGB input. This circuit is synchronized with the video input color burst signal extracted by BFP (burst flag pulses) during superimposition, preventing any unnatural color disturbance
due to switching between RGB and video input.
This oscillator circuit generates the RGB color burst
signal. An attached variable resistor can be used to
change the amplitude of the color burst signal and to
adjust its phase relative to the video color burst signal.
This oscillator circuit remains in the free-running state
when there is no video input.
Amplitude
C carrier color signal
(combining of R-Y and B-Y)
R-Y
B-Y
Time
θ
90°
RGB
COMPOSITE
VCXO
1
µs
3.58
YS
90°
θ
EB - EY
ER - EY
3.58MHz (90°)
Fig. 5
6
OUT
R13
1.2kΩ
XT1
3.58MHz
Fig. 7
+
Balanced
modulator
7
– 5dB
VIDEO IN
HDP
(Half Down
Pulse)
B-Y
Balanced
modulator
3.58MHz (0°)
8
C7
82pF
C6
68pF
R14
560Ω
R-Y
9
TC1
20pF
Carrier
color signal
Fig. 8
(5) During superimposition, video input can be lowered
by about 5dB using an HDP (half-down pulse), darkening the background and making RGB input easier to
see.
Multimedia ICs
BA7230LS
•Input waveform and timing chart
VIDEO IN
1VP-P
CB
SYNC
VH
∗
TTL LEVEL ( 1)
VL
PCP
VH
∗
TTL LEVEL ( 1)
VL
BFP
VH
∗
TTL LEVEL ( 1)
VL
RGB IN
0.7VP-P
VH
∗
TTL LEVEL ( 1)
HDP
VL
VH
YS
∗
TTL LEVEL ( 2)
VL
COMPOSITE OUT
from RGB
2VP-P
CB
SUPER
IMPOSE
2VP-P
CB
CB: COLOR BURST
VH: 3.0V ~ VCC
VH: 2.0V ~ VCC
∗1 VL: 0 ~ 0.8V
∗2 VL: 0 ~ 0.4V
Fig. 9
•Electrical characteristic curves
80
3580.5
f0 = 3579.545kHz
VIN = 0.1VP-P
60
50
40
30
20
10
0
0
1
2
3
4
5
6
7
POWER SUPPLY VOLTAGE: VCC (V)
Fig. 10 Quiescent current vs.
power supply voltage
8
FREQUENCY: f (cap. lock) (Hz)
600
FREQUENCY: f (free run) (kHz)
QUIESCENT CURRENT: IQ (mA)
f0 = 3579.545kHz
70
3580.0
3579.5
3579.0
+ lock
400
+ cap
200
f0 = 0
– cap
– 200
– lock
– 400
– 600
3578.5
3
4
5
6
7
POWER SUPPLY VOLTAGE: VCC (V)
Fig. 11 VCXO free-run frequency vs.
power supply voltage
3
4
5
7
6
POWER SUPPLY VOLTAGE: VCC (V)
Fig. 12 Capture range and
lock range (!) vs.
power supply voltage
7
FREQUENCY: f (cap. lock) (Hz)
Multimedia ICs
BA7230LS
600
f0 = 3579.545kHz
+ lock VCC = 5V
400
+ cap
200
f0 = 0
– 200
– cap
– 400
– lock
– 600
0
100 200 300
800
400 500 600 700
INPUT VOLTAGE: VIN (mVp-p)
Fig. 13 Capture range and
lock range (@) vs. input
voltage
1µF
1kΩ
+
+
1µF
LPF
•
VCC
2.8 ± 0.2
0.3
+ 0.1
– 0.05
2
23
24
SZIP24
+4
+5
1µF
(ROHM)
Fig. 15
9.9 ± 0.5
2.0Min.
5.8 ± 0.2
1
300Ω C10
300Ω
Q1, Q2: 2SC2021
2.54 ± 0.25
8
C15
17
Q1
C11 1µF
3kΩ
3kΩ
0.5 ± 0.1
20pF
18
VCC
Q2
External dimensions (Units: mm)
0.889
20pF
C14
33pF
1.2mH L1 R16 1kΩ
Fig. 14
21.8 ± 0.2
0.5MHz
1.2mH L 2 R17 1kΩ
33pF
C13
(2) The VCXO remains in a
free-running state except
during superimposition.
(4) Pin 4 (B-YIN) and pin 5
(R-Y IN) have high impedance and are susceptible
to the effects of noise and
other external factors during pattern generation. For
this reason, we recommend adding the circuit in
Fig. 15 to lower the input
impedance. Adding this circuit can also reduce carrier
leakage.
C12
When only RGB is input, connect VIDEO IN (pin 20) to
GND with a 1µF capacitor, and synchronize PCP and
BFP to RGB.
(3) Input pins with pedestal clamps cannot be left open
and must be grounded with a low impedance. When
not used, ground with a 1µF capacitor.
∗Input pins with pedestal clamps:
YIN (pin 3), B-YIN (pin 4), R-YIN (pin 5), VIDEO IN (pin 20)
Additional
circuit
notes
•(1)Operation
RGB and video inputs should be synchronized.