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TBA950
Television signal Processing Circuit
National
Semiconductor
General Description
The TBA950-2 is a monolithic integrated circuit for
pulse separation and line synchronization in TV receivers
with transistor output stages.
The TBA950 comprises the sync separator with noise
suppression, the frame pulse integrator, the phase com-
parator, a switching stage for automatic changeover of
TV Circuits
TBA950-2 Television Signal Processing Circuit
noise immunity, the line oscillator with frequency-range
limiter, a phase control circuit and the output stage.
It delivers prepared frame sync pulses for triggering the
frame oscillator. The phase comparator may be switched
for video recording operation. Due to the large scale of
integration, few external components are needed.
Connection and Block Diagrams
DuaMmLine Package
LINE DI? DRIVE -
- LINE FREtlOENCY FRESH
2 LINE Fnzuuzucv CAPACITOR
DuaI-In-Line Package, Order Number TBA950-2
See NS Package N14A
2 must contain CAPACITOR
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m Ouad-ln-Line P ck Or er Number TB _ O
svm: SEFARATO8 m: -2., - LINE nvancx PULSE m a MN, d A950 2
See NS Package N14C
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FRAME SYNC w,-'., -SmTCN DELAY CAPACITOR
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[ttPUT SIGNAL
This Material Copyrighted By Its Respective
Manufacturer
Z'OSBVQL
TBA950-2
Absolute Maximum Ratings
All voltages are referred to pin 1
Recommended Operating Conditions
(For operating circuits Figures 4 ands)
Electrical Characteristics TA ' 25°C, f0 = 15,625 Hz in the test circuit Figure 2 (Note 1)
l3, Supply Current (Figure 6) 45 mA ls. Input Current During Sync Pulse >5 izA
15, Input Current 2 mA VIN p-p, Composite Video Input Signal 3 (1 to 6)V
V5, Input Voltage -6V I10, Input Current During Line Flyback Pulse 0.2 to 2 mA
12, Output Current 22 mA l8, Switbh-Over Current >2 mA
V2, Output Voltage 12V td, Time Difference Between the Output Pulse
is, Switch-Over Current for Video Recording 5 mA at Pin 2 and the Line Flyback Pulse at 10 <20 us
I10, Flyback Peak Pulse Current 5 mA l3, Current Consumption (Figure ti) 345 mA
V11, Phase Correction Voltage tr to V3 TA, Ambient Operating Temperature Range 0°C to +60°C
TA. Ambient Temperature 60°C
SYMBOL CHARACTERISTIC CONDITIONS MIN TYP MAX UNITS
V7 Amplitude of the Frame Pulse >8 V
t7 Frame Pulse Durations >150 us
ROUT 7 Output Resistance at Pin 7 7.5 10 13 k9
(High State)
t2 Output Pulse Duration Typical Ranges 25 28 us
V2 Res Residual Output Voltage I2 = 20 mA <0. 55 V
to Oscillator Frequency C13/1= 1O nF, R14/1= 10.5 kf2 14063 15625 17187 Hz
iAfF Frequency PuiHn Range 400 1000 Hz
+-AfH Frequency Holding Range Typical Ranges 400 1000 Hz
dfo/dtd Slope of Phase Comparator 2 kHz/us
Control Loop
dtd/dtp Gain of Phase Control 20
tp Phase Shift Between Leading Typical Range 0 3.5 Ms
Edge of Composite Video
Signal and Line Flyback Pulse
(Note 2) Adjustable by V11
Functional Description
Note 1: By modification of the frequency-determining network at pins 13 and 14, these le can also be used for other line frequencies.
Note 2: The limited flyback pulse should overlap the video signal sync pulse on both edges.
The sync separator separates the synchronizing pulses
from the composite video signal. The noise inverter
circuit, which needs no external components, in con-
nection with an integrating and differentiating network
frees the synchronizing signal from distortion and noise.
The frame sync pulse is obtained by multiple integration
and limitation of the synchronizing signal, and is avail.
able at pin 7. The RC network, hitherto required between
sync separator and frame oscillator is no longer needed.
Since the frame sync pulse duration at pin 7 is subject
to production spreads, it is recommended to use the
leading edge of this pulse for triggering.
The frequency of the line oscillator is determined by a
10 nF polystyrene capacitor at pin 13 which is charged
and discharged periodically by 2 internal current sources.
The external resistor at pin 14 defines the charging
current and consequently in conjunction with the oscil-
lator capacitor the line frequency.
The phase comparator compares the sawtoothvoltage of
the oscillator with the line sync pulses. Simultaneously,
an AFC voltage is generated which influences the oscil-
lator frequency. A frequency range limiter restricts the
frequency holding range.
The oscillator sawtooth voltage, which is in a fixed ratio
to the line sync pulses, is compared with the flyback
pulse in the phase control circuit, in this way compen-
sating all drift of delay times in driver and line output
stage. The correct phase position and hence the hori-
zontal position of the picture can be adjusted by the
10 kn potentiometer connected to pin 11. Within the
adjustable range the output pulse duration (pin 2) is
constant. Any larger displacements of the picture,
e.g., due to non-symmetrical picture tube, should not
be corrected by the phase potentiometer, since in all
cases the flyback pulse must overlap the sync pulse on
both edges (Figure 3).
This Material Copyrighted By Its Respective Manufacturer
Functional Description (Continued)
The switching stage has an auxiliary function. When the
2 signals supplied by the sync separator and the phase
control circuit, respectively, are in synchronism, a
saturated transistor is in parallel with the integrated
2 kn resistor at pin 9. Thus the time constant of the
filter network at pin 4 increases and consequently
reduces the pulI-in range of the phase comparator cir-
cuit for the synchronized state to approximately 50 Hz.
This arrangement ensures disturbance-free operation.
For video recording operation, this automatic switchover
can be blocked by a positive current fed into pin 8,
e.g., via a resistor cdnnected to pin 3. It may also be use-
ful to connect a resistor of about 680 n or 1 k9 between
pin 9 and earth. The capacitor at pin 4 may be lowered,
e.g., to 0.1 pF. These alterations do not significantly
influence the normal operation of the IC and thus do
not need to be switched. '
The output stage delivers at pin 2 output pulses of
duration and polarity suitable for driving the line driver
stage. If the supply voltage goes down (e.g., by switching
off the mains) a built-in protection circuitensures defined
line frequency pulses down to V3 = 4V and shuts off
when V3 falls below 4V, thus preventing pulses of
undefined duration and frequency. Conversely, if the
supply voltage rises, pulses defined in duration and fre-
quency will appear at the output pin as soon as V3
reaches 4.5V. In the range between V3 = 4.5V and full
supply the shape and frequency of the output pulses are
practically constant.
FLVIACK
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FIGURE 3. Phase Relationships
150 usq
PULSES
-, VCC
TBASSII an“
VIDEO INPUT
SIGNAL ION
EE?, "
210% _
FREQUENCY
UIIE FLYBACK
PULSES
- tt P "
*lnput circuitry must be optimized
FIGURE 4. Operating Circuit (Thyristor Output Stage)
3'096V81
Material Copyrighted By Its Respective Manufacturer
TBA950-2
Functional Description (Continued)
>150us
PULSES
0.33 "
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SIGNAL vm
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'input circuitry must be optimized
FIGURE 5. Another Possibility for Line
Frequency Adjustment (Transistor Output Stage)
Rs (9)
0 " 20 30
FIGURE 6. Graph for Determining
the Supply Series Resistor, Rs
This Material Copyrighted By Its Respective Manufacturer
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Datasheets for electronic components.
National Semiconductor was acquired by Texas Instruments.
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This file is the datasheet for the following electronic components:
TBA950 - product/tba950?HQS=TI-nu|I-nu|I-dscatalog-df-pf-nuII-wwe
