ca3224 Intersil Corporation, ca3224 Datasheet - Page 3

• Manufacturer Part Number: ca3224
• Description: Automatic Picture Tube Bias Control Circuit
• Manufacturer: Intersil Corporation

Test Circuit
HORIZONTAL
VERTICAL
INPUT
INPUT
V
V
V
MODE SWITCH
CHAN
IN1
IN2
IN3
1 IN
2
1
2
3
+
-
COMP
FREQ
GND
0.047
0.047
0.047
3
g
1
M
AMPLIFER
F
F
F
NO. 1
CAPACITOR
1
2
3
4
5
6
7
8
9
10
11
CA3224E
1
HOLD
3
2
SET-UP
SENSE
STATE
GND
OPEN
21
9
BUFFER
BIAS
AMP
x 1
17
16
15
14
13
12
22
21
20
19
18
CHAN
1 OUT
+
47 F
20K
20
S
S
S
+10V
1
V
1
1
22
CC
3.32K
1.50K
CHAN
FIGURE 1. FUNCTIONAL BLOCK DIAGRAM
B
A
B
A
B
A
2 IN
S
4
V
V
0.12 F
V
2
0.12 F
0.12 F
BYPASS
3.65K
3.65K
3.65K
OUT1
OUT2
OUT3
V
15
REF
COMP
V
FREQ
-
+
B
A
REF
g
1.5K
5
1.0K
+20V
M
V
AMPLIFER
BIAS
NO. 2
CA3224E
+10V
VERT
IN
CAPACITOR
8
1
3
2
HOLD
8-58
19
BUFFER
Device Description and Operation
(See Figures 1, 2, 4 and 5)
During the vertical retrace interval, 13 horizontal sync pulses
are counted. On the 14th sync pulse the auto-bias pulse out-
put goes high. This is used to set the RGB drive of the com-
panion chroma/luma circuit to black level. The auto-bias pulse
stays high for 7 horizontal periods during the auto-bias cycle.
On the 15th horizontal sync pulse, the internal logic initiates
the setup interval. During the setup interval, the cathode cur-
rent is increased to a reference value (A in Figure 5) through
the action of the grid pulse. The cathode current causes a
voltage drop across R
program pulse output results in a reference voltage at V
(summing point) which causes capacitor C
voltage proportional to the reference cathode current. The
setup interval lasts for 3 horizontal periods.
On the 18th horizontal sync pulse the grid pulse output goes
high, which through the grid pulse amplifier/inverter, causes
the cathode current to decrease. The decrease in cathode
current results in a positive recovered voltage pulse with
respect to the setup reference level at the V
The positive recovered voltage pulse is summed with a nega-
tive voltage pulse caused by the program pulse output going
low (cutting off Diode D
R
is fed through capacitor C
The difference signal is amplified in the transconductance
amplifier and charges the hold capacitor C
the buffer amplifier, adjusts the bias on the driver circuit.
Components R
program pulse and the recovered pulse just cancel at the
desired cathode cutoff level.
2
AMP
HORIZ
). Any difference between the positive and negative pulses
x 1
10
IN
2 OUT
CHAN
18
PULSE
GRID
OUT
CHAN
11
3 IN
S
6
, R
LOGIC
1
COMP
FREQ
, and R
+
-
S
7
g
. This voltage drop, together with the
PULSE
AMPLIFER
1
M
PROG
OUT
1
12
and switching in resistors R
NO. 3
to the transconductance amplifier.
2
CAPACITOR
must be chosen such that the
1
3
HOLD
2
17
PULSE
AUTO
BIAS
OUT
BUFFER
13
AMP
SWITCH
MODE
x 1
2
CHAN
3 OUT
S
1
, which, through
16
ADJUST
summing point.
LEVEL
to charge to a
AUTO
BIAS
14
1
and
S