TEA2029 STMICROELECTRONICS [STMicroelectronics], TEA2029 Datasheet - Page 27

• Manufacturer Part Number: TEA2029
• Description: APPLICATION NOTE
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Figure 51 : Block Diagram of the Vertical Deflection Stage
V.6.1 - Frame sync extraction
The main duty of this stage is to extract the frame
sync pulses contained in composite sync signal.
Figure 52 : Sync. Extractor Block Diagram
Two current generators are used to charge and
discharge the integrated capacitor ”C”. The dis-
charge generator (I
ite sync signal.
The V
During frame trace, the capacitor is discharged at
each line sync pulse thereby generating a V of
-0.94V with respect to 5.6V and then recovers the
charge by current ”I
mains low.
The discharge time is 27 s at the first line sync
inversion applied to comparator input. The voltage
”V
comparator ”C
pulse when ”V
The overall arrangement behaves as an integrator
and will therefore suppress any noise susceptible
Composite
C
Composite
Separator
Sync.
” then falls from 5.6V to 0.2V and triggers the
Frame
Sync.
Sync.
Reference
C
Block
H/2
across capacitor is :
5.6V
I
I
C
C
C
+
0
” crosses the 2.8V level.
” which will deliver a frame sync
I
D
C
C
2.8V
+ I
”. The comparator output re-
C
D
Frame Logic
) is driven by the compos-
V
&
C
2.8V
Reset
Free
I
D
1
t
C
SYNC
Frame
Sync.
I
I
C = 35pF
C
C
50/60Hz
= 2 A
+
Reset
I
D
= 9 A
I
60
5
Generator
Sawtooth
C5
to be present on input signal.
An external capacitor Pin 20 can be added to the
integrated capacitor C to increase the frame sync
time constant.
V.6.2 - Frame saw-tooth generator
Figure 53
The frame saw-tooth is generated by an external
RC network on Pin 5.
The time constant ”R5 C5” is much higher than
the frame period. Therefore, the generated saw-
tooth is quite linear.
The network is discharged by an internal transistor,
controlled by the frame logic block.
Frame
TEA2028 - TEA2029 APPLICATION NOTE
FRAME LOGIC
BLOCK
x 1
R5
Frame
(64 s)
Reset
(200V)
60Hz
+E
24
3
+E
Sawtooth
Frame
50/60Hz
Output
2.7M
Amplifier
R5
Power
V
I
+
5
I
I
C5
470nF
Y
Y
I
60
Frame
Yoke
Top of Picture
+
3
R3
2.2k
Bottom of Picture
Frame Sawtooth
Output
t
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