TDA8145_04 STMICROELECTRONICS [STMicroelectronics], TDA8145_04 Datasheet - Page 5

• Manufacturer Part Number: TDA8145_04
• Description: TV EAST/WEST CORRECTION CIRCUIT FOR SQUARE TUBES
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Figure 6. Application Circuit with Keystone Correction
CIRCUIT OPERATION
(see the shematic diagram)
A differential amplifier OP1 is driven by a vertical
frequency sawtooth current of ± 33µA which is
produced via an external resistor fromthe saw-
tooth voltage. The non–inverting input of this am-
plifier is connected with a reference voltage
corresponding to the DC level of the sawtooth volt-
age. This DC voltage should be adjustable for the
keystone correction. The rectified output current of
this amplifier drives the parabola networkwhich
provides a parabolic output current.
This output current produces the corresponding
voltage due to the voltage drop across the external
resistor at pin 7.
Pin 1
Voltage
V
FRAME
R1 =
66µA
V
Keystone
FRAME
Adj.
PP
Line Transformer
2
1
100kΩ
(L.T.)
RT1
If the input is overmodulated (> 40µA) the internal
current is limited to 40µA. This limitation can be
used for suppressing the parasitic parabolic cur-
rent generated during the flyback time of the frame
sawtooth.
A comparator OP2 is driven by the parabolic cur-
rent. The second input of the comparator is con-
nected with a horizontal frequency sawtooth
voltage the DC level of which can be changed by
the external circuitry for the adjustment of the pic-
ture width.
The horizontal frequency pulse–width modulated
output signal drives the final stage. It consists of a
class D push–pull output amplifier that drives, via
an external inductor, the diode modulator.
LM
5
3
L1
10mH
4.7kΩ
TDA8145
R3
R2
12kΩ
Hfly
from L.T.
Pin-cushion
adjustment
RT2
4
47kΩ
7
8
R5
C3
4.7nF
6
RT3
1kΩ
D1
1N4148
R4
18kΩ
C2
100nF
TDA8145
H. Width
V
C1
47nF
S
5/9