TELEFUNKEN P152MT CHASSIS TX90/EU INTERNAL VIEW.

TDA8218 HORIZONTALAND VERTICAL DEFLECTION CIRCUIT

DESCRIPTION
The TDA8218 is an horizontal and vertical deflection
circuit with super sandcastle generator. Used
with automatic PAL/SECAM decoder TEA5640,
this IC permits a complete low-cost solution for
PAL/SECAMapplications.


DIRECT FRAME-YOKE DRIVE (± 1A)
.COMPOSITE VIDEO SIGNAL INPUT CAPABILITY
.FRAME OUTPUT PROTECTION AGAINST
SHORT CIRCUITS
.PLL .SUPER SANDCASTLE OUTPUT
.VERYFEW EXTERNALCOMPONENTS
.VERYLOW COST POWER PACKAGE
.STABLE FRAME BLANKING PULSE, GENERATED
BY EXTERNAL RC, FOR COMPATIBILITY
WITH TEA 5640

GENERAL DESCRIPTION
The TDA8218 performs all the video and power
functions required to provide signals for the line
driver and frame yoke.

It contains:
• A synchronization separator
• An integrated frame separator without external
components
• A saw-tooth generator for the frame
• A power amplifier for direct drive of frame yoke
(short circuit protected)
• An open collector output for the line driver
• A line phase detector and a voltage control oscillator
• A super sandcastle generator.


The oscillator thresholds are internally fixed by
resistors. The discharge of the capacitor depends
on the internal resistor R4. The control voltage is
applied on resistor R5.
The sync-pulse drives the current in the comparator.
The line flyback integrated by the external net
work gives on pin 13 a saw tooth, the DC offset of
this saw tooth is fixed by VC. The comparator
output provides a positive current for the part of the
signal on pin 13 greater than to VC and a negative
current for the other part.When the line flyback and
the video signal are synchronized, the output of the
comparatoris analternativelynegativeand positive
current. The frame sync-pulse inhibits the comparator
to prevent frequency drift of the line oscillator
on the frame beginning.

Line output (Pin 17)
It is an open-collector output. The output positive
pulse time is 28µs for a 64µs period. The oscillator
thresholds are internally fixed by resistors. The
oscillator is synchronized during the last half free
run period. The input current during the charge of
the capacitor is less than 100nA.
Frame output amplifier
This amplifier is able to drive directly the frame
yoke. Its output is short circuit and overload protected;
it contains also a thermal protection.
The line flyback detection is provided by a comparator
which compares the input line flyback pulse
to an internal reference. The burst gate pulse position
is fixed by the externalRC network (pin 14). It
is referenced to the middle of the line flyback.
The frame blanking generator is amonostable with
external R.C. The start blanking pulse is triggered
by the falling edge of the frame saw-tooth (Pin 2).
The reset is provided by a comparator which compares
the capacitor voltage during its charge to an
internal threshold fixed by resistors.
The frame blanking time is defined by :
Tfb = 0.613 ⋅ R.C.
This pulse is available onSuperSand Castle output
(Pin 19).
Remark : For compatability with TEA5640, frame
blanking time must be larger than 1.15ms with
centered value @ 1.35ms (R = 100kΩ ± 1%,
C = 22nF ± 5%)


TEA5040S WIDE BAND VIDEO PROCESSOR

DESCRIPTION
The TEA5040S is a serial bus-controlled videoprocessing
device which integrates a complex architecture
fulfilling multiple functions.

GENERAL DESCRIPTION
Brief Description
This integrated circuit incorporates the following
features :
- a synchro and two video inputs
- a fixed video output
- a switchable video output
- normal Y, R-Y, B-Y TV mode inputs
- double set of R, G, B inputs
- brightness, contrast and saturation controls as
wellon aR,G, B picture ason a normalTVpicture
- digital control inputs by means of serial bus
- peak beam current limitation
- average beam current limitation
- automaticdrive and cut-off controls.

Video Switch
The video switch has three inputs :
- an internal video input (pin 39),
- an external video input (pin 37),
- a synchro input (pin 41),
and two outputs :
- an internal video output (pin 40),
- a switchable video output (pin 42)
The 1Vpp composite video signal applied to the
internal video input is multiplied by two and then
appears as a 2Vpp low impedance composite
video signal at the output. This signal is used to
deliver a 1Vpp/75W composite video signal to the
peri-TV plug.
The switchable video output canbe any of the three
inputs.When the Int/Ext one active bit word is high
(address number 5), the internal video input is
selected. If not, either a regeneratedsynchro pulse
or the external video signal is directed towards this
output depending on the level of the Sync/Async
one active bit word (address number 4). As this
output is to be connected to the synchro integrated
circuit, RGB information derived from an external
source via the Peri-TV plug canbedisplayed on the
screen, the synchronization of the TV-set being
then made with an external video signal.
When RGB information is derived from a source
integrated in the TV-set, a teletext decoder for
example, the synchronization can be made either
on the internal video input (in case of synchronous
data) or on the synchro input (in case of asynchronous
data).
R, G, B Inputs
There are two sets of R, G, B inputs : one is to be
connected to the peri-TV plug (Ext R, G, B), the
second one to receive the information derived from
the TV-set itself (Int R, G, B).
In order to have a saturation control on a picture
coming from the R, G, B inputs too, it is necessary
to getR-Y, B-Y and Y signals from R, G, B information
: this is performed on the first matrix that
receives the three 0.9Vp (100% white) R, G, B
signals and delivers the corresponding Y, R-Y, B-Y
signals. These ones are multiplied by 1.4 in order
to make the R-Y and B-Y signals compatible with
the R-Y and B-Y TV mode inputs. The desired R,
G, B inputs are selected by means of 3 switches
controlled by the two fast blanking signal inputs. A
high level on FB external pin selects the external
RGB sources. The three selected inputs are
clamped in order to give the required DC level at
the output of this firstmatrix. Thethree not selected
inputs are clamped on a fixed DC level.
Y, R-Y, B-Y Inputs
The 2Vpp composite video signal appearing at the
switchable output of the video switch (pin 42) is
driven through the subcarrier trap and the luminance
delay line with a 6 dB attenuation to the Y
input (1Vpp ; pin 12). In order to make this 1Vpp
(synchro to white) Y signal compatible with the
1Vpp (black to white) Y signal delivered by the first
matrix, it is necessary to multiply it by a coefficient
of 1.4.

R, G, B Insertion Pulse (fast blanking)
A R, G, B source has also to provide an insertionpulse.
Since this integrated circuit can be directly
connected to two different sources, it is necessary
then to have two separate insertion pulse inputs
(pin 8-9). Fast blanking can be inhibited by a one
active bit word. The two fast blanking inputs carry
out an OR function to insert R, G, B sources into
TV picture. The external fast blanking (FB ext.)
selects the appropriate R, G, B source.
Controls
The four brightness, contrastand saturationcontrol
functions are direct digitally controlled without using
digital-to-analog converters.
The contrast control of the Y channel is obtained
by means of a digital potentiometer which is an
attenuator including several switchable cells directly
controlled by a 5 active bit word (address
number 1). The brightness control is also made by
a digital potentiometer (5 active bit word, address
number 0). Since a + 3dB contrast capability is
required, the Y signal value could be up to 0.7Vpp
nominal. For both functions, the control characteristics
are quasi-linear.
In each R-Y and B-Y channel, a six-cell digital
attenuator is directly controlled by a 6 active bit
word (address number 6 and 7). The tracking
needed to keep the saturation constant when
changing the contrast has to be done externally by
the microcontroller. Furthermore, colour can be
disabledby blankingR-Y andB-Ysignals using one
active bit word (address number 2) to drive the
one-chip colour ON/OFF switch.
Second Matrix, Clamp, Peak Clipping, Blanking
The second matrix receives the Y, R-Y and B-Y
signals and delivers the corresponding R, G, B
signals. As it is required to have the capability of +
6dB saturation, an internal gain of 2 is applied on
both R-Y and B-Y signals.
A low clipping level is included in order to ensure a
correct blanking during the line and frame retraces.
Ahigh clipping level ensures thepeakbeamcurrent
limitation. These limitations are correct only if the
DC bias of the three R, G, B signals are precise
enough. Therefore a clamp has been added in
each channel in order to compensate for the inaccuracy
of the matrix.
Sandcastle Detector And Counter
The three level supersandcastle is used in the
circuit to deliver the burst pulse (CLP), the horizontal
pulse (HP), and the composite vertical and
horizontal blanking pulse (BLI). This last one is
regenerated in the counter which delivers a new
composite pulse (BL) in which the vertical part lasts
23 lines when the vertical part of the supersandcastle
lasts more than 11 lines.
The TEA5040S cannot work properly if this minimum
duration of 11 lines is not ensured.
The counterdelivers different pulses neededcircuit
and especially the line pulses 17 to 23 used in the
automatic drive and cut-off control system.
Automatic Drive And Cut-off Control System
Cut-off and drive adjustments are no longer required
with this integrated circuit as it has a sample
and hold feedback loop incorporating the final
stages of the TV-set. This system works in a sequentialmode.
For this purpose, special pulses are
inserted in G, R and B channels. During the lines
17, 18 and 19, a ”drive pulse” is inserted respectively
in the green, red and blue channels. The line
20 is blanked on the three channels. During the
lines 21, 22 and 23, a ”quasi cut-off pulse” is
inserted respectively in the green, red and blue
guns.
The resulting signal is then applied to the input of
a voltage controlled amplifier. In the final stages of
the TV-set, the current flowing in each green, red
and blue cathode is measured and sent to the
videoprocessorby a current source.
The three currents are added together in a resistor
matrix which can be programmed to set the ratio
between the three currents in order to get the
appropriate colour temperature. The output of the
matrix forms a high impedance voltage source
which is connectedto the integratedcircuit (pin 34).
Same measurement range between drive and cutoff
is achieved by internally grounding an external
low impedance resistor during lines 17, 18 and 19.
This is due to the fact that the drive currents are
about one hundred times higher than the cut-off
and leakage currents.
Each voltage appearing sequentially on the wire
pin 34 is then a function of specific cathode current
:
- When a current due to a drive pulse occurs, the
voltage appearing on the pin 34 is compared
within the IC with an internal reference, and the
result of the comparison charges or discharges
an external appropriate drive capacitor which
stores the value during the frame. This voltage is
applied to a voltage controlled amplifier and the
system works in such a waythat the pulse current
drive derived from the cathode is kept constant.
- During the line 20, the three guns of the picture
tube are blanked. The leakagecurrent flowing out
of the final stages is transformed into a voltage which is stored by an external leakage capacitor
to be used later as a reference for the cut-off
current measurement.
- When a current due to a cut-off pulse occurs, the
voltage appearing on the pin 34 is compared
within the ICto the voltagepresenton the leakage
memory. Anappropriate externalcapacitor is then
charged or discharged in such a way that the
difference between each measured current and
the leakage current is kept constant, and thus the
quasi cut-off current is kept constant.
AverageBeam Current Limitation
The total current of the three guns is integrated by
means of an internal resistor and an external capacitor
(pin 36) and thencompared with a programmable
voltage reference(pin 38). When 70% of the
maximum permitted beam current is reached, the
drive gain begins to be reduced ; to do so, the
amplitude of the inserted pulse is increased.
In order to keep enough contrast, the maximum
drive reduction is limited to 6dB. If it is not sufficient,
the brightness is suppressed.



TEA2261/0 SWITCH MODE POWER SUPPLY CONTROLLER

DESCRIPTION
The TEA2260/61 is a monolithic integrated circuit
for the use in primary part of an off-line switching
mode power supply.
All functions required for SMPS control under normal
operating, transient or abnormal conditions
are provided.
The capability of working according to the “master-
slave” concept, or according to the “primary
regulation” mode makes the TEA2260/61 very
flexible and easy to use. This is particularly true for
TV receivers where the IC provides an attractive
and low cost solution (no need of stand-by auxiliary
power supply).

GENERAL DESCRIPTION
The TEA2260/61 is an off-line switch mode power
supply controller. The synchronization function
and the specific operation in stand-by mode make
it well adapted to video applications such as TV
sets, VCRs, monitors, etc..
The TEA2260/61 can be used in two types of architectures:
– Master/Slave architecture. In this case, the
TEA2260/61 drives the power transistor according
to the pulse width modulated signals generated
by the secondary located master circuit. A
pulse transformer provides the feedback (see
Figure 1).
– Conventional architecture with linear feedback
signal (feedback sources: optocoupler or transformer
winding) (see Figure 2).
Using the TEA2260/61, the stand-by auxiliary
power supply, often realized with a small but costly
50Hz transformer, is no longer necessary. The
burst mode operation of the TEA2260/61 makes
possible the control of very low output power
(down to less than 1W) with the main power transformer.
When used in a master/slave architecture, the
TEA2260/61 and also the power transistor turn-off
can be easily synchronized with the line transformer.
The switching noise cannot disturb the picture
in this case.
As an S.M.P.S. controller, the TEA2260/61 features
the following functions:
– Power supply start-up (with soft-start)
– PWM generator
– Direct power transistor drive (+1.2A, -2.0A)
– Safety functions: pulse by pulse current limitation,
output power limitation, over and under voltage
lock-out.
S.M.P.S. OPERATING DESCRIPTION
Starting Mode - Stand By Mode
Power for circuit supply is taken from the mains
through a high value resistor before starting. As
long as VCC of the TEA2260/61 is below VCC start,
the quiescent current is very low (typically 0.7mA)
and the electrolytic capacitor across VCC is linearly
charged. When VCC reaches VCC start (typically
10.3V), the circuit starts, generating output pulses
with a soft-starting. Then the SMPS goes into the
stand-by mode and the output voltage is a percentage
of the nominal output voltage (e.g. 80%).
To do this, the TEA2260/61 contains all the functions
required for primary mode regulation: a fixed
frequency oscillator, a voltage reference, an error
amplifier and a pulse width modulator (PWM).
For transmission of low power with a good efficiency
in stand-by, an automatic burst generation system
is used, in order to avoid audible noise.
Normal Mode (Secondary Regulation)
The normal operating of the TV set is obtained by
sending to the TEA2260/61 regulation pulses generated
by a regulator located in the secondary side
of the power supply.
This architecture uses the “Master/Slave Concept”,
advantages of which are now well-known
especially the very high efficiency in Stand-by
mode, and the accurate regulation in Normal
mode.
Stand-by mode or normal mode are obtained by
supplying or not the secondary regulator. This can
be ordonnered for example by a microprocessor in
relation with the remote control unit.
Regulation pulses are applied to the TEA2260/61
through a small pulse-transformer to the IN input
(Pin 2). This input is sensitive to positive square
pulses. The typical threshold of this input is 0.85V.
The frequency of pulses coming from the secondary
regulator can be lower or higher than the frequency
of the starting oscillator.
The TEA2260/61 has no soft-starting system
when it receives pulses from the secondary. The
soft-start must be located in the secondary regulator.
Due to the principle of the primary regulation, pulses
generated by the starting system automatically
disappear when the voltage delivered by the
SMPS increases.
Stand-by Mode - Normal Mode Transition
During the transition there are simultaneously
pulses coming from the primary and secondary
regulators.
These signals are not synchronized and some
care has to be taken to ensure the safety of the
switching power transistor.
A very sure and simple way consist in checking the
transformer demagnetization state.
– A primary pulse is taken in account only if the
transformer is demagnetized after a conduction
of the power transistor required by the secondary
regulator.
– A secondary pulse is taken in account only if the
transformer is demagnetized after a conduction
of the power transistor required by the primary
regulator.
With this arrangement the switching safety area of
the power transistor is respected and there is no
risk of transformer magnetization.
The magnetization state of the transformer is
checked by sensing the voltage across a winding
of the transformer (generally the same which supplies
the TEA2261). This is made by connecting a
resistor between this winding and the demagnetization
sensing input of the circuit (Pin 1).
SECURITY FUNCTIONS OF THE TEA2260 (see flowchart below)
Undervoltage Detection. This protection works in
association with the starting device “VCC switch”
(see paragraph Starting-mode - stand-by mode). If
VCC is lower than VCCstop (typically 7.4V) output
pulses are inhibited, in order to avoid wrong operation
of the power supply or bad power transistor
drive.
Overvoltage Detection. If VCC exceeds VCCmax
(typically 15.7V) output pulses are inhibited. Restarting
of the power supply is obtained by reducing
VCC below VCCstop.
Current Limitation of the Power Transistor. The
current is measured by a shunt resistor. A double
threshold system is used:
– When the first threshold (VIM1) is reached, the
conduction of the power transistor is stopped until
the end of the period: a new conduction signal
is needed to obtain conduction again.
– Furthermore as long as the first threshold is
reached (it means during several periods), an external
capacitor C2 is charged. When the voltage
across the capacitor reaches VC2 (typically
2.55V) the output is inhibited. This is called the
“repetitive overload protection”. If the overload
disappears before VC2 is reached, C2 is discharged,
so transient overloads are tolerated.
– Second current limitation threshold (VIM2). When
this threshold is reached the output of the circuit
is immediately inhibited. This protection is helpful
in case of hard overload for example to avoid the
magnetization of the transformer.
Restart of the Power Supply. After stopping due
to VC2, VIM2, VCCMax or VCCstop triggering, restart
of the power supply can be obtained by the
normal operating of the “VCC switch” but thanks to
an integrated counter, if normal restart cannot be
obtained after three trials, the circuit is definitively
stopped. In this case it is necessary to reduce VCC
below approximately 5V to reset the circuit. From a
practical point of view, it means that the power
supply has to be temporarily disconnected from
any power source to get the restart.

SECURITY FUNCTIONS OF THE TEA2261
Undervoltage Detection. This protection works in
association with the starting device “VCC switch”
(see paragraph Starting-mode - stand-by mode). If
VCC is lower than VCCstop (typically 7.4V) output
pulses are inhibited, in order to avoid wrong operation
of the power supply or bad power transistor
drive.
Overvoltage Detection. If VCC exceeds VCCmax
(typically 15.7V) output pulses are inhibited and
the external capacitor C2 is charged as long as
VCC is higher than VCC stop. Restarting of the
power supply is obtained by reducing VCC below
VCCstop except if the voltage across C2 reaches
VC2 (typically 2.55V) (refer to “Restart of the power
supply” paragraph).In this last case, the circuit is
definitively stopped.
Current Limitation of the Power Transistor. The
current is measured by a shunt resistor. A double
threshold system is used:
– When the first threshold (VIM1) is reached, the
conduction of the power transistor is stopped until
the end of the period: a new conduction signal
is needed to obtain conduction again.
– Furthermore as long as the first threshold is
reached (it means during several periods), an external
capacitor C2 is charged. When the voltage
across the capacitor reaches VC2 (typically
2.55V) the output is inhibited. This is called the
“repetitive overload protection”. If the overload
disappears before VC2 is reached, C2 is discharged,
so transient overloads are tolerated.
– Second current limitation threshold (VIM2). When
this threshold is reached the output of the circuit
is immediately inhibited. This protection is helpful
in case of hard overload for example to avoid the
magnetization of the transformer.
Restart of the Power Supply. After stopping due
to VIM2, VCCMax or VCCstop triggering, restart of
the power supply can be obtained by the normal
operating of the “VCC switch” VCC switch sequency
from VCCstop to VCCstart. After stopping due to
VC2 threshold reaching, the circuit is definitively
stopped. In this case it is necessary to reduce VCC
below approximately 5V to reset the circuit. From a
practical point of view, it means that the power
supply has to be temporarily disconnected from
any power source to get the restart.