The SHARP 70GS-61S chassiS GA-10 t's based on the VCT38XX DIGIT3000 from ITT/MICRONAS technology which was allowing to develop a complete digital television with one chip solution toghether with a one chip for digital audio processing.THEREFORE THE SHARP CHASSIS GA-10 is the highest integrated DIGITAL CHASSIS FOR CRT TUBE TELEVISION APPLICATION.
It's entirely based around the ITT/MICRONAS DIGIT3000 technology for VIDEO and AUDIO digital processing.
........ And it's highly complex ............ and very critical..............
It's Divided by 2 layers of parts:
- Componenents side : All Power signal parts....
and some ROM.......... Tuner...........SCART Socket.
- Solder side: All signal processing parts + solder part for power parts.
Other signal acquisition IF stages are based around PHILIPS semiconductors technology.
Some parts like audio amplifier and Frame output stages are based on THOMSON semiconductors.
The chassis has a very unusual circuits development particularly in the power stages like:
- POWER SUPPLY
- LINE DEFLECTION + E/W CORRECTION + EHT
- FRAME DEFLECTION OUTPUT.
Repairing these it's a NIGHTMARE !!!! From the complexity of the circuits to the design of the layouts of the PCB and the critical general composition sometimes it's very hard to repair, and even because they were failing often with various frequent defects mainly caused by dry joints causing further faults in geometrical sequence .
IT RUNS DISCRETELY WARM !!!!
SHARP 70GS-61S CHASSIS GA-10 (F7315BMN6) CIRCUITS DESCRIPTIONS:
SHARP 70GS-61S CHASSIS GA-10 [GA10] Switching power supply unit:
An inexpensive power supply unit which may be used for video display devices is provided. The unit saves power when supplying power to a light load, such as during remote control standby. Power for a controller which controls each part of a video display device is supplied from the switching power supply. Power consumption of the switching power supply is reduced by extending an OFF period setting for the switching power supply when operation of a display drive circuit is turned off.
The present invention relates to switching circuitry wherein a low-loss "drive" inductance is "charged" and "discharged" to provide the energy for turning a power switch on and off. The drive-inductance and a tapped-winding transformer co-act in a novel manner to provide a large "sweep-out" current that quickly turns off the power switch, the sweep-out time being extremely short.
FIELD OF THE INVENTION
The present invention relates to the field of power supply units generally, and more specifically to exemplary power supply units which are used for video display devices including television sets and display monitors for computers.
BACKGROUND OF THE INVENTION
Conventional power supply units for video display devices, for example television sets, use a single converter for supplying the power necessary for heavy loads such as during watching TV and for light loads when the TV is turned off or in the remote control standby state by employing a self-excited power supply (hereafter referred to as "switching power supply"). This system, however, causes great loss in the remote control standby state because the energy continuously regenerates in the switching element and transformer. (Refer to Japanese Laid-open Patent H4-172090.)
One alternative system is to employ two power supplies: a main power supply and a power supply for a control means such as a microcomputer (hereafter referred to generically as the microcomputer).
1. A switching power supply unit comprising:
ON period control means for controlling an ON period;
minimum OFF period setting means for setting a minimum time amount for an OFF period; and
OFF period control means for controlling the setting of the OFF period;
wherein said ON period control means controls output voltage of said switching power supply unit by controlling said ON period while said OFF period control means fixes the OFF period to the minimum time amount for the OFF period; and
said OFF period control means controls output voltage of said switching power supply unit by controlling the OFF period while said ON period control means fixes the ON period to a fixed minimum time amount of said ON period responsive to the output voltage of said switching power supply unit dropping.
2. A power supply unit according to claim 1, wherein said controller for the main converter comprises an OFF period setting circuit, wherein said OFF period setting circuit determines an OFF period based on a specified minimum OFF period and a period controlled by a feedback signal.
3. A power supply unit according to claim 1, including a transformer and wherein said controller for the main converter comprises: a capacitor
an ON period controller which discharges voltage charged in said capacitor and controls an ON period based on the terminal voltage of said capacitor and a control voltage in response to a feedback signal;
an OFF period controller which charges said capacitor and controls the OFF period based on the terminal voltage of said capacitor and the control voltage in response to a feedback signal; and
a transformer reset detector which suppresses the turning on of a switching device during resonance of said transformer.
4. A power supply unit according to claim 1, wherein said controller for the main converter comprises: a capacitor;
means for setting a specified voltage; and
an OFF period controller which increases charge voltage of said capacitor to said specified voltage at a first rate of charge and then further increases voltage at a rate of charge less than the first rate of charge, to a voltage above said specified voltage to a control voltage, the control voltage being based on a feedback signal.
5. A power supply unit according to claim 1, wherein said controller for the main converter comprises an OFF period controller, the OFF period controller comprising: means for setting a specified voltage and
means for charging voltage of a capacitor to said specified voltage at substantially high speed,
wherein said means for charging voltage is used for determining a minimum OFF period.
6. A power supply unit according to claim 1 wherein the power supply unit is a power supply unit for a video display device, the power supply unit comprising: an output voltage terminal for outputting multiple levels of voltage;
a first output voltage terminal for outputting voltage applied to a display drive circuit of the video display device using a switching means; and
a second output voltage terminal for outputting voltage applied to a controller which controls on and off of said switching means;
whereby an OFF period setting of the power supply unit is extended when said switching means is turned off.
7. A power supply unit according to claim 1 wherein the power supply unit is a power supply unit for a video display device, the power supply unit comprising: a first switching power supply for supplying power supply voltage to a display drive circuit of the video display device and a second switching power supply for supplying power supply voltage to a signal processor and a range of controllers; whereby an OFF period setting of said second switching power supply is extended when said first switching power supply is turned off by a switching means.
8. A switching power supply unit comprising: i) a first switching power supply unit;
ii) a second switching power supply unit for supplying power for less load than said first switching power supply unit supplies, said second switching power supply unit comprising:
a) means for switching on or off power for said first switching power supply unit;
b) ON period control means for controlling ON period;
c) minimum OFF period setting means for setting a minimum time amount of an OFF period;
d) OFF period control means for controlling the setting of the OFF period;
said OFF period control means controls output voltage of said second switching power supply unit by controlling the OFF period when said ON period control means fixes the ON period to a fixed minimum ON period while said second switching power supply unit switches off power for said first switching power supply unit.
9. A power supply unit according to claim 8, wherein the power supply unit is a power supply unit for a video display device, and the first load is a display drive circuit of the video display device.
1. Switching circuitry comprising:
a control switch;
a drive circuit comprising a charge circuit and a discharge circuit;
a drive inductor;
a drive transformer;
said drive transformer having a charge primary winding, a discharge primary winding, and a secondary winding;
said charge circuit comprising said secondary winding and a series circuit of said drive inductor, said control switch, and said charge primary winding;
whereby when said control switch assumes its ON state, a charge current in said charge circuit charges said drive inductor, and produces an enabling signal in said secondary winding;
a power switch adapted to permit the flow of an electric current therethrough;
means for applying said enabling signal to said power switch, for causing said power switch to quickly and positively assume its ON state and for permitting the flow of a load current;
said discharge circuit comprising said secondary winding and a series circuit of said drive inductor and said discharge primary winding;
whereby, when said control switch assumes its OFF state, the energy of said charged drive inductor directly produces a discharge current, and said discharge current in said discharge circuit produces a disabling signal in said secondary winding;
means for applying said disabling signal to said power switch for causing said power switch to quickly and positively assume its OFF state, and for terminating the flow of the load current.
2. The invention of claim 1, wherein said control switch and said power switch are transistors.
3. The invention of claim 1, wherein said discharge circuit further comprises blocking diode means for blocking said charge current from flowing in said discharge circuit.
4. The invention of claim 1, including a second drive circuit; means for causing said power switch to function as a control switch for said second drive circuit,
whereby said drive circuits are cascaded.
5. The invention of claim 1, including a plurality of control switches, a corresponding plurality of drive circuits associated with respective ones of said control switches, and a corresponding plurality of power switches associated with respective ones of said drive circuits; means for causing said control-circuit means to conductivate said individual control switches of said plurality of control switches in a sequential timed manner;
whereby said individual drive circuits and said individual power switches are energized in a corresponding sequential timed manner.
6. Switching circuitry comprising: a control transistor;
control-circuit means for controlling the ON/OFF state of said control transistor;
a drive circuit comprising a charge circuit and a discharge circuit;
a drive inductor;
a drive transformer;
said drive transformer having a charge primary winding, a discharge primary winding, and a secondary winding;
said charge circuit comprising said secondary winding, blocking diode means for blocking said charge current from flowing in said discharge circuit and a series circuit of said drive inductor, said control switch, and said charge primary winding;
whereby, when said control transistor assumes its ON state, a charge current in said charge circuit charges said drive inductor, and produces an enabling signal in said secondary winding;
a power transistor adapted for the flow of an electric current therethrough;
means for applying said enabling signal to said power transistor, for causing said power transistor to quickly and positively assume its ON state;
said discharge circuit comprising said said secondary winding and a series circuit of said drive inductor and said discharge primary winding;
whereby, when said control transistor assumes its OFF state, the energy of said charged drive inductor directly produces a discharge current, and said discharge current in said discharge circuit produces an opposite-polarity disabling signal in said secondary winding;
said disabling signal being a short-interval, high-magnitude, sweep-out current;
means for applying said disabling signal to said power transistor for causing said power transistor to quickly and positively assume its OFF state.
7. The invention of claim 6, including means for controlling the timing of said control circuit means.
In the field of electronics, it is frequently necessary to "transform" one form of electricity to another form, such transformations taking place in circuits known as power sources, converters, inverters, rectifiers, etc. Some of these circuits function, for example, to transform AC to DC, DC to AC, DC of one voltage to DC of another voltage, etc. Such circuits often use switches of one type or another; but, unfortunately, switches tend to raise severe problems -- such as power loss, low efficiency, undesirable heating, transients, impaired lifetimes, and the like.
OBJECTIVES AND DRAWINGS
It is, therefore, the principal objective of the present invention to provide improved switching circuitry.
It is another objective of the present invention to provide improved switching circuitry that provides extremely fast turn-off.
It is still another objective of the present invention to provide improved switching circuitry wherein a low-power system controls a high-power system.
It is a further objective of the present invention to provide improved switching circuitry adapted to be used in a cascaded manner, in order to control the switching of even higher power systems.
It is a further objective of the present invention to provide improved switching circuitry adapted to be used in a timed manner, in order to provide higher-power and smoother-power systems.
VCT 3831A/B Video/Controller/Teletext IC Family:
The VCT 38xxA/B is an IC family of high-quality singlechip
TV processors. Modular design and a submicron
technology allow the economic integration of features
in all classes of TV sets. The VCT 38xxA/B family is
based on functional blocks contained and approved in
existing products like VDP 3120B, TPU 3050S, and
Each member of the family contains the entire video,
display, and deflection processing for 4:3 and 16:9 50/
60-Hz TV sets. The integrated microcontroller is supported
by a powerful OSD generator with integrated
teletext acquisition which can be upgraded with onchip
page memory. With volume control and audio
input select the basic audio features for mono TV sets
are integrated. An overview of the VCT 38xxA/B single-
chip TV processor family is given in Fig. 1–1 on
The VCT 38xxA/B family offers a rich feature set, covering
the whole range of state-of-the-art 50/60-Hz TV
In comparison to the VCT 38xxA the VCT 38xxB offers
the following features:
– one additional composite video input
– analog luma/chroma adder for video output
– closed caption module
– additional 12k character ROM.
1.1.1. Video Features
– four composite video inputs (VCT 38xxA)
– five composite video inputs (VCT 38xxB)
– analog YCrCb input, two S-VHS inputs
– Y/C adder for video output (VCT 38xxB only!)
– composite video monitor
– multistandard color decoder (1 crystal)
– multistandard sync decoder
– black-line detector
– adaptive 2H comb filter Y/C separator
– horizontal scaling (0.25 to 4)
– black-level expander
– dynamic peaking
– soft limiter (gamma correction)
– color transient improvement
– programmable RGB matrix
– analog RGB/Fastblank input
– half-contrast switch
– picture frame generator
– scan velocity modulation output
– high-performance H/V deflection
– angle and bow correction
– separate ADC for tube measurements
– EHT compensation
1.1.2. Microcontroller Features
– 8-bit, 10-MHz CPU (65C02)
– 96 kB program ROM on chip
– 1 kB program RAM on chip
– memory banking
– 16-input, 16-level interrupt controller
– patch module for 10 ROM locations
– two 16-bit reloadable timers
– capture compare module
– watchdog timer
– 14-bit PWM for voltage synthesis
– four 8-bit PWMs
– 10-bit ADC with 15:1 input MUX
– I2C bus master interface
– 24 programmable I/O ports
– closed caption module (VCT 38xxB only!)
1.1.3. OSD Features
– 3 kB OSD RAM on chip
– WST level 1.5 compliant
– WST level 2 parallel attributes
– 32 foreground/background colors
– programmable color look-up table
– 1024 mask programmable characters (VCT 38xxA)
– 2000 mask programmable characters (VCT 38xxB)
– 24 national languages
(Latin, Cyrillic, Greek, Arabic, Farsi, Hebrew)
– character matrix 8x8, 8x10, 8x13, 10x8, 10x10, 10x13
– vertical soft scroll
– 4-color mode for user font
1.1.4. Teletext Features
– four programmable video inputs (VCT 38xxA)
– five programmable video inputs (VCT 38xxB)
– acquisition is independent from display part
– adaptive data slicer
– signal quality detection
– WST, PDC, VPS, and WSS acquisition
– high-level command language
– EPG, FLOF, and TOP support
– 10 pages memory on chip
– up to 500 pages with external SRAM
1.1.5. Audio Features
– three mono inputs
– two mono outputs
– programmable channel select
– volume control for one mono channel
1.1.6. General Features
– submicron CMOS technology
– low-power standby mode
– single 20.25-MHz crystal
– 64-pin PSDIP package
– 128-pin PMQFP package
The VCT 38xxA/B includes complete video, display,
and deflection processing. In the following sections the
video processing part of the VCT 38xxA/B will be
named VDP for short.
All processing is done digitally, the video front-end and
video back-end are interfacing to the analog world.
Most functions of the VDP can be controlled by software
via I2C bus slave interface (see Section 2.14. on
2.2. Video Front-end
This block provides the analog interfaces to all video
inputs and mainly carries out analog-to-digital conversion
for the following digital video processing. A block
diagram is given in Fig. 2–1.
Most of the functional blocks in the front-end are digitally
controlled (clamping, AGC, and clock-DCO). The
control loops are closed by the Fast Processor (‘FP’)
embedded in the video decoder.
2.2.1. Input Selector
Up to eight analog inputs can be connected. Four
inputs (five in case of VCT 38xxB) are for input of composite
video or S-VHS luma signal. These inputs are
clamped to the sync back porch and are amplified by a
variable gain amplifier. Two chroma inputs can be
used for connection of S-VHS carrier-chrominance signal.
These inputs are internally biased and have a
fixed gain amplifier. For analog YCrCb signals (e.g.
from DVD players) one of the selected luminance
inputs is used together with CBIN and CRIN inputs.
The composite video input signals are AC-coupled to
the IC. The clamping voltage is stored on the coupling
capacitors and is generated by digitally controlled current
sources. The clamping level is the back porch of
the video signal. S-VHS chrominance is also AC-coupled.
The input pin is internally biased to the center of
the ADC input range. The chrominance inputs for
YCrCb need to be AC-coupled by 220 nF clamping
capacitors. It is strongly recommended to use 5-MHz
anti-alias low-pass filters on each input. Each channel
is sampled at 10.125 MHz with a resolution of 8 bit and
a clamping level of 128.
2.2.3. Automatic Gain Control
A digitally working automatic gain control adjusts the
magnitude of the selected baseband by +6/–4.5 dB in
64 logarithmic steps to the optimal range of the ADC.
The gain of the video input stage including the ADC is
213 steps/V with the AGC set to 0 dB. The gain of the
chrominance path in the YCrCb mode is fix and
adapted to a nominal amplitude of 0.7 Vpp. However, if
an overflow of the ADC occurs an extended signal
range from 1 Vpp can be selected.
2.2.4. Analog-to-Digital Converters
Two ADCs are provided to digitize the input signals.
Each converter runs with 20.25 MHz and has 8 bit resolution.
An integrated bandgap circuit generates the
required reference voltages for the converters.
2.2.5. Digitally Controlled Clock Oscillator
The clock generation is also a part of the analog frontend.
The crystal oscillator is controlled digitally by the
control processor. The clock frequency can be
adjusted within ±150 ppm.
2.2.6. Analog Video Output
The input signal of the Luma ADC is available at the
analog video output pin. The signal at this pin must be
buffered by a source follower. The output voltage is
2 V, thus the signal can be used to drive a 75-Ω line.
The magnitude is adjusted with an AGC in 8 steps
together with the main AGC.
In case of VCT 38xxB it is possible to enable a Y/Cadder.
The analog sum of the selected luma and
chroma input signals is available at the video output
pin. This allows recording of S-VHS input signals via
2.3. Adaptive Comb Filter
The adaptive comb filter is used for high-quality luminance/
chrominance separation for PAL or NTSC signals.
The comb filter improves the luminance resolution
(bandwidth) and reduces interferences like
cross-luminance and cross-color artifacts. The adaptive
algorithm can eliminate most of the mentioned
errors without introducing new artifacts or noise.
A block diagram of the comb filter is shown in Fig. 2–2.
The filter uses two line delays to process the information
of three adjacent video lines. To have a fixed
phase relationship of the color subcarrier in the three
channels, the system clock (20.25 MHz) is locked to
the color subcarrier. This allows the processing of all
color standards and substandards using a single crystal
The CVBS signal in the three channels is filtered at the
subcarrier frequency by a set of bandpass/notch filters.
The output of the three channels is used by the
adaption logic to select the weighting that is used to
reconstruct the luminance/chrominance signal from
the 4 bandpass/notch filter signals.The comb filter
uses the middle line as reference, therefore, the comb
filter delay is one line. If the comb filter is switched off,
the delay lines are used to pass the luma/ chroma signals
from the A/D converters to the luma/ chroma outputs.
Thus, the comb filter delay is always one line.
Various parameters of the comb filter are adjustable,
hence giving to the user the ability to adjust his own
desired picture quality.
Two parameters (KY, KC) set the global gain of luma
and chroma comb separately; these values directly
weigh the adaption algorithm output. In this way, it is
possible to obtain a luma/chroma separation ranging
from standard notch/bandpass to full comb decoding.
The parameter KB allows to choose between the two
proposed comb booster modes. This so-called feature
widely improves vertical high-to-low frequency transitions
areas, the typical example being a multiburst to
DC change. For KB=0, this improvement is kept moderate,
whereas, in case of KB=1, it is maximum, but
the risk to increase the “hanging dots” amount for
some given color transitions is higher.
Using the default setting, the comb filter has separate
luma and chroma decision algorithms; however, it is
possible to switch the chroma comb factor to the current
luma adaption output by setting CC to 1.
Fig. 2–2: Block diagram of the adaptive comb filter (PAL mode)
1H Delay Line
1H Delay Line
Luma / Chroma Mixers
Another interesting feature is the programmable limitation
of the luma comb amount; proper limitation, associated
to adequate luma peaking, gives rise to an
enhanced 2-D resolution homogeneity. This limitation
is set by the parameter CLIM, ranging from 0 (no limitation)
to 31 (max. limitation).
The DAA parameter (1:off, 0:on) is used to disable/
enable a very efficient built-in “rain effect” suppressor;
many comb filters show this side effect which gives
some vertical correlation to a 2-D uniform random
area, due to the vertical filtering. This unnatural-looking
phenomenon is mostly visible on tuner images,
since they are always corrupted by some noise; and
this looks like rain.
2.4. Color Decoder
A block diagram of the color decoder is shown in Fig.
2–4. The luma as well as the chroma processing, is
shown here. The color decoder provides also some
special modes, e.g. wide band chroma format which is
intended for S-VHS wide bandwidth chroma.
If the adaptive comb filter is used for luma chroma separation,
the color decoder uses the S-VHS mode processing.
The output of the color decoder is YCrCb in a
With off-air or mistuned reception, any attenuation at
higher frequencies or asymmetry around the color subcarrier
is compensated. Four different settings of the
IF-compensation are possible:
– flat (no compensation)
– 6 dB/octave
– 12 dB/octave
– 10 dB/MHz
The last setting gives a very large boost to high frequencies.
It is provided for SECAM signals that are
decoded using a SAW filter specified originally for the
Fig. 2–3: Frequency response of chroma
Fig. 2–4: Color decoder
1 H Delay
Luma / CVBS Luma
The subcarrier frequency in the demodulator is generated
by direct digital synthesis; therefore, substandards
such as PAL 3.58 or NTSC 4.43 can also be
2.4.3. Chrominance Filter
The demodulation is followed by a low-pass filter for
the color difference signals for PAL/NTSC. SECAM
requires a modified low-pass function with bell-filter
characteristic. At the output of the low-pass filter, all
luma information is eliminated.
The low-pass filters are calculated in time multiplex for
the two color signals. Three bandwidth settings (narrow,
normal, broad) are available for each standard.
For PAL/NTSC, a wide band chroma filter can be
selected. This filter is intended for high bandwidth
chroma signals, e.g. a non-standard wide bandwidth
2.4.4. Burst Detection / Saturation Control
In the PAL/NTSC-system the burst is the reference for
the color signal. The phase and magnitude outputs of
the color demodulator are gated with the color key and
used for controlling the phase-locked-loop (APC) of the
demodulator and the automatic color control (ACC) in
The ACC has a control range of +30...−6 dB.
Color saturation can be selected once for all color
standards. In PAL/NTSC it is used as reference for the
ACC. In SECAM the necessary gains are calculated
For SECAM decoding, the frequency of the burst is
measured. Thus, the current chroma carrier frequency
can be identified and is used to control the SECAM
processing. The burst measurements also control the
color killer operation; they are used for automatic standard
detection as well.
2.4.5. Color Killer Operation
The color killer uses the burst-phase/burst-frequency
measurement to identify a PAL/NTSC or SECAM color
signal. For PAL/NTSC, the color is switched off (killed)
as long as the color subcarrier PLL is not locked. For
SECAM, the killer is controlled by the toggle of the
burst frequency. The burst amplitude measurement is
used to switch-off the color if the burst amplitude is
below a programmable threshold. Thus, color will be
killed for very noisy signals. The color amplitude killer
has a programmable hysteresis.
2.4.6. Automatic Standard Recognition
The burst-frequency measurement is also used for
automatic standard recognition (together with the status
of horizontal and vertical locking) thus allowing a
completely independent search of the line and color
standard of the input signal. The following standards
can be distinguished:
– PAL B,G,H,I
– PAL M
– PAL N
– PAL 60
– NTSC M
– NTSC 44
For a preselection of allowed standards, the recognition
can be enabled/disabled via I2C bus for each standard
If at least one standard is enabled, the VCT 38xxA/B
regularly checks the horizontal and vertical locking of
the input signal and the state of the color killer. If an
error exists for several adjacent fields a new standard
search is started. Depending on the measured line
number and burst frequency, the current standard is
For error handling the recognition algorithm delivers
the following status information:
– search active (busy)
– search terminated, but failed
– found standard is disabled
– vertical standard invalid
– no color found
2.4.7. PAL Compensation/1-H Comb Filter
The color decoder uses one fully integrated delay line.
Only active video is stored.
The delay line application depends on the color standard:
– NTSC: 1-H comb filter or color compensation
– PAL: color compensation
– SECAM: crossover switch
In the NTSC compensated mode, (Fig. 2–6c), the color
signal is averaged for two adjacent lines. Thus,
cross-color distortion and chroma noise is reduced. In the NTSC comb filter mode, the delay line
is in the composite signal path, thus allowing reduction
of cross-color components, as well as cross-luminance.
The loss of vertical resolution in the luminance
channel is compensated by adding the vertical detail
signal with removed color information.
2.6. Black-line Detector
This function is available for versions with panorama
In case of a letterbox format input video, e.g. Cinemascope,
PAL+ etc., black areas at the upper and lower
part of the picture are visible. It is suitable to remove or
reduce these areas by a vertical zoom and/or shift
The VCT 38xxA/B supports this feature by a letterbox
detector. For every field the number of black lines at
the upper and lower part of the picture are measured
and stored in the I2C-register BLKLIN. To adjust the
picture amplitude, the CPU reads this register, calculates
the vertical scaling coefficient and transfers the
new settings, e.g. vertical sawtooth parameters, horizontal
scaling coefficient etc., to the scaler and the
Letterbox signals containing logos on the left or right
side of the black areas are processed as black lines,
while subtitles, inserted in the black areas, are processed
as non-black lines. Therefore, the subtitles are
visible on the screen. To suppress the subtitles, the
vertical zoom coefficient is calculated by selecting the
larger number of black lines only. Dark video scenes
with a low contrast level compared to the letterbox
area are indicated by the BLKPIC bit.
2.7. Test Pattern Generator
The YCrCb outputs can be switched to a test mode
where YCrCb data are generated digitally in the
VCT 38xxA/B. Test patterns include luma/chroma
ramps and flat fields.
2.8. Video Sync Processing
Fig. 2–10 shows a block diagram of the front-end sync
processing. To extract the sync information from the
video signal, a linear phase low-pass filter eliminates
all noise and video contents above 1 MHz. The sync is
separated by a slicer; the sync phase is measured. A
variable window can be selected to improve the noise
immunity of the slicer. The phase comparator measures
the falling edge of sync, as well as the integrated
The sync phase error is filtered by a phase-locked loop
that is computed by the FP. All timing in the front-end
is derived from a counter that is part of this PLL, and it
thus counts synchronously to the video signal.
A separate hardware block measures the signal back
porch and also allows gathering the maximum/minimum
of the video signal. This information is processed
by the FP and used for gain control and clamping.
For vertical sync separation, the sliced video signal is
integrated. The FP uses the integrator value to derive
vertical sync and field information.
The information extracted by the video sync processing
is multiplexed onto the hardware front sync signal
(FSY) and is distributed to the rest of the video processing
The data for the vertical deflection, the sawtooth, and
the East-West correction signal is calculated by the
VCT 38xxA/B. The data is buffered in a FIFO and
transferred to the back-end by a single wire interface.
Frequency and phase characteristics of the analog
video signal are derived from PLL1. The results are fed
to the scaler unit for data interpolation and orthogonalization
and to the clock synthesizer for line-locked
clock generation. Horizontal and vertical syncs are
latched with the line-locked clock.
2.9. Display Processing
In the display processing the conversion from digital
YCrCb to analog RGB is carried out. A block diagram
is shown in Fig. 2–18 on page 23. In the luminance
processing path, contrast and brightness adjustments
and a variety of features, such as black-level expansion,
dynamic peaking and soft limiting, are provided.
In the chrominance path, the CrCb signals are converted
to 4:4:4 format and filtered by a color transient
improvement circuit. The YCrCb signals are converted
by a programmable matrix to RGB color space.
The display processor provides separate control settings
for two pictures, i.e. different coefficients for a
‘main’ and a ‘side’ picture.
The digital OSD insertion circuit allows the insertion of
a 5-bit OSD signal. The color space for this signal is
controlled by a partially programmable color look-up
table (CLUT) and contrast adjustment.
The OSD signals and the display clock are synchronized
to the horizontal flyback. For the display clock, a
gate delay phase shifter is used. In the analog backend,
three 10-bit digital-to-analog converters provide
the analog output signals.
2.9.1. Luma Contrast Adjustment
The contrast of the luminance signal can be adjusted
by multiplication with a 6-bit contrast value. The contrast
value corresponds to a gain factor from 0 to 2,
where the value 32 is equivalent to a gain of 1. The
contrast can be adjusted separately for main picture
and side picture.
2.9.2. Black-Level Expander
The black-level expander enhances the contrast of the
picture. Therefore the luminance signal is modified
with an adjustable, non-linear function. Dark areas of
the picture are changed to black, while bright areas
remain unchanged. The advantage of this black-level
expander is that the black expansion is performed only
if it will be most noticeable to the viewer.
The black-level expander works adaptively. Depending
on the measured amplitudes ‘Lmin’ and ‘Lmax’ of the
low-pass-filtered luminance and an adjustable coefficient
BTLT, a tilt point ‘Lt’ is established by
Lt = Lmin + BTLT (Lmax - Lmin).
Above this value there is no expansion, while all luminance
values below this point are expanded according
Lout = Lin + BAM (Lin - Lt)
A second threshold, Ltr, can be programmed, above
which there is no expansion.
2.9.3. Dynamic Peaking
Especially with decoded composite signals and notch
filter luminance separation, as input signals, it is necessary
to improve the luminance frequency characteristics.
With transparent, high-bandwidth signals, it is
sometimes desirable to soften the image.
In the VCT 38xxA/B, the luma response is improved by
‘dynamic’ peaking. The algorithm has been optimized
regarding step and frequency response. It adapts to
the amplitude of the high-frequency part. Small AC
amplitudes are processed, while large AC amplitudes
stay nearly unmodified.
The dynamic range can be adjusted from −14 to
+14 dB for small high-frequency signals. There is separate
adjustment for signal overshoot and for signal
undershoot. For large signals, the dynamic range is
limited by a non-linear function that does not create
any visible alias components. The peaking can be
switched over to “softening” by inverting the peaking
term by software.
The center frequency of the peaking filter is switchable
from 2.5 MHz to 3.2 MHz. For S-VHS and for notch filter
color decoding, the total system frequency responses
for both PAL and NTSC are shown in Fig. 2–14.
Transients, produced by the dynamic peaking when
switching video source signals, can be suppressed via
the priority bus.
2.9.4. Digital Brightness Adjustment
The DC-level of the luminance signal can be adjusted
by adding an 8-bit number in the luminance signal path
in front of the softlimiter.
With a contrast adjustment of 32 (gain+1) the signal
can be shifted by 100%. After the brightness addition,
the negative going signals are limited to zero. It is
desirable to keep a small positive offset with the signal
to prevent undershoots produced by the peaking from
being cut. The digital brightness adjustment works
separately for main and side picture.
2.9.5. Soft Limiter
The dynamic range of the processed luma signal must
be limited to prevent the CRT from overload. An appropriate
headroom for contrast, peaking and brightness
can be adjusted by the TV manufacturer according to
the CRT characteristics. All signals above this limit will
be ‘soft’-clipped. A characteristic diagram of the soft
limiter is shown in Fig. 2–15. The total limiter consists
of three parts:
Part 1 includes adjustable tilt point and gain. The gain
before the tilt value is 1. Above the tilt value, a part
(0...15/16) of the input signal is subtracted from the
input signal itself. Therefore, the gain is adjustable
from 16/16 to 1/16, when the slope value varies from
0 to 15. The tilt value can be adjusted from 0 to 511.
Part 2 has the same characteristics as part 1. The subtracting
part is also relative to the input signal, so the
total differential gain will become negative if the sum of
slope 1 and slope 2 is greater than 16 and the input
signal is above the both tilt values (see characteristics).
Finally, the output signal of the soft limiter will be
clipped by a hard limiter adjustable from 256 to 511.
2.9.6. Chroma Interpolation
A linear phase interpolator is used to convert the
chroma sampling rate from 10.125 MHz (4:2:2) to
20.25 MHz (4:4:4). All further processing is carried out
at the full sampling rate.
2.9.7. Chroma Transient Improvement
The intention of this block is to enhance the chroma
resolution. A correction signal is calculated by differentiation
of the color difference signals. The differentiation
can be selected according to the signal bandwidth,
e.g. for PAL/NTSC/SECAM or digital component signals,
respectively. The amplitude of the correction signal
Small noise amplitudes in the correction signal are
suppressed by an adjustable coring circuit. To eliminate
‘wrong colors’, which are caused by over and
undershoots at the chroma transition, the sharpened
chroma signals are limited to a proper value automatically.
2.9.8. Inverse Matrix
A 6-multiplier matrix transcodes the Cr and Cb signals
to R-Y, B-Y, and G-Y. The multipliers are also used to
adjust color saturation in the range of 0 to 2. The coefficients
are signed and have a resolution of 9 bits.
There are separate matrix coefficients for main and
side pictures. The matrix computes:
The initialization values for the matrix are computed
from the standard ITUR (CCIR) matrix:
For a contrast setting of CTM+32, the matrix values
are scaled by a factor of 64 (see Table 2–4 on
2.9.9. RGB Processing
After adding the post-processed luma, the digital RGB
signals are limited to 10 bits. Three multipliers are
used to digitally adjust the white drive. Using the same
multipliers an average beam current limiter is implemented
(see Section 2.10.1. on page 24).
2.9.10. OSD Color Look-up Table
The VCT 38xxA/B has five input lines for an OSD signal.
This signal forms a 5-bit address for a color
look-up table (CLUT). The CLUT is a memory with 32
words where each word holds a RGB value.
Bits 0 to 3 (bit 4=0) form the addresses for the ROM
part of the OSD, which generates full RGB signals (bit
0 to 2) and half-contrast RGB signals (bit 3).
Bit 4 addresses the RAM part of the OSD with 16
freely programmable colors, addressable with bit 0 to
3. The programming is done via the I2C bus.
The amplitude of the CLUT output signals can be
adjusted separately for R, G, and B via the I2C bus.
The switchover between video RGB and OSD RGB is
done via the priority decoder.
2.9.11. Picture Frame Generator
When the picture does not fill the total screen (height
or width too small) it is surrounded with black areas.
These areas (and more) can be colored with the picture
frame generator. This is done by switching over
the RGB signal from the matrix to the signal from the
OSD color look-up table.
The width of each area (left, right, upper, lower) can be
adjusted separately. The generator starts on the right,
respectively lower side of the screen and stops on the
left, respectively upper side of the screen. This means,
it runs during horizontal, respectively vertical flyback.
The color of the complete border can be stored in the
programmable OSD color look-up table in a separate
address. The format is 3 x 4-bit RGB. The contrast can
be adjusted separately.
The picture frame generator includes a priority master
circuit. Its priority is programmable and the border is
generated only if the priority is higher than the priority
of the other sources (video/OSD). Therefore, the border
can be underlay or overlay depending on the picture
CRT Measurement and Control
The display processor is equipped with an 8-bit
PDM-ADC for all measuring purposes. The ADC is
connected to the SENSE input pin, the input range is 0
to 1.5 V. The bandwidth of the PDM filter can be
selected; it is 40/80 kHz for small/large bandwidth setting.
The input impedance is more than 1 MΩ.
Cutoff and white-drive current measurement are carried
out during the vertical blanking interval. They
always use the small bandwidth setting. The current
range for the cutoff measurement is set by connecting
a sense resistor to the MADC input. For the white-drive
measurement, the range is set by using another sense
resistor and the range select switch 2 output pin
(RSW2). During the active picture, the minimum and
maximum beam current is measured. The measurement
range can be set by using the range select
switch 1 pin (RSW1) as shown in Fig. 2–19 and Fig. 2–
20. The timing window of this measurement is programmable.
The intention is, to automatically detect
letterbox transmission or to measure the actual beam
current. All control loops are closed via the external
In each field two sets of measurements can be taken:
a) The picture tube measurement returns results for
– cutoff R
– cutoff G
– cutoff B
– white-drive R or G or B (sequentially)
b) The picture measurement returns data on
– active picture maximum current
– active picture minimum current
The tube measurement is automatically started when
the cutoff blue result register is read. Cutoff control for
RGB requires one field only, whereas a complete
white-drive control requires three fields. If the measurement
mode is set to ‘offset check’, a measurement
cycle is run with the cutoff/white-drive signals set to
zero. This allows to compensate the MADC offset as
well as input the leakage currents. During cutoff and
white-drive measurements, the average beam current
limiter function (see Section 2.10.3. on page 26) is
switched off and a programmable value is used for the
brightness setting. The start line of the tube measurement
can be programmed via I2C bus, the first line
used for the measurement, i.e. measurement of cutoff
red, is 2 lines after the programmed start line.
The picture measurement must be enabled by the control
microprocessor after reading the min./max. result
registers. If a ‘1’ is written into bit 2 in subaddress 25,
the measurement runs for one field. For the next measurement
a ‘1’ has to be written again. The measurement
is always started at the beginning of active video.
The vertical timing for the picture measurement is programmable,
and may even be a single line. Also the
signal bandwidth is switchable for the picture measurement.
Two horizontal windows are available for the picture
measurement. The large window is active for the entire
active line. Tube measurement is always carried out
with the small window.
2.10.3. Average Beam Current Limiter
The average beam current limiter (BCL) uses the
SENSE input for the beam current measurement. The
BCL uses a different filter to average the beam current
during the active picture. The filter bandwidth is
approx. 2 kHz. The beam current limiter has an automatic
offset adjustment that is active two lines before
the first cutoff measurement line.
The beam current limiter function is located in the
front-end. The data exchange between the front-end
and the back-end is done via a single-wire serial interface.
The beam current limiter allows the setting of a threshold
current. If the beam current is above the threshold,
the excess current is low-pass filtered and used to
attenuate the RGB outputs by adjusting the white-drive
multipliers for the internal (digital) RGB signals, and
the analog contrast multipliers for the analog RGB
inputs, respectively. The lower limit of the attenuator is
programmable, thus a minimum contrast can always
be set. During the tube measurement, the ABL attenuation
is switched off. After the white-drive measurement
line it takes 3 lines to switch back to BCL limited
drives and brightness.
Typical characteristics of the ABL for different loop
gains are shown in Fig. 2–22; for this example the tube
has been assumed to have square law characteristics.
Fig. 2–22: Beam current limiter characteristics: beam
current output vs. drive BCL threshold: 1
2.10.4. Analog RGB Insertion
The VCT 38xxA/B allows insertion of external analog
RGB signals. The RGB signal is key-clamped and
inserted into the main RGB by the Fast-Blank switch.
The external RGB input can be overlaid or underlaid to
the digital picture. The external RGB signals can be
adjusted independently as regards DC level (brightness)
and magnitude (contrast).
All signals for analog RGB insertion (RIN, GIN, BIN,
FBLIN) must be synchronized to the horizontal flyback,
otherwise a horizontal jitter will be visible. The
VCT 38xxA/B has no means for timing correction of
the analog RGB input signals.
2.10.5. Fast-Blank Monitor
The presence of external analog RGB sources can be
detected by means of a Fast-Blank monitor. The status
of the Fast-Blank input can be monitored via an I2C
bus register. There is a 2 bit information, giving static
and dynamic indication of a Fast-Blank signal. The
static bit is directly reading the Fast-Blank input line,
whereas the dynamic bit is reading the status of a
flip-flop triggered by the negative edge of the Fast-
With this monitor logic it is possible to detect if there is
an external RGB source active and if it is a full screen
insertion or only a box. The monitor logic is connected
directly to the FBLIN pin.
Synchronization and Deflection
The synchronization and deflection processing is distributed
over front-end and back-end. The video
clamping, horizontal and vertical sync separation and
all video related timing information are processed in
the front-end. Most of the processing that runs at the
horizontal frequency is programmed on the internal
Fast Processor (FP). Also the values for vertical and
East/West deflection are calculated by the FP software.
The generation of horizontal and vertical drive signals
can be synchronized to the video timing extracted in
the front-end or to a free running line counter in the
2.11.1. Deflection Processing
The deflection processing generates the signals for the
horizontal and vertical drive (see Fig. 2–24). This block
contains two phase-locked loops:
– PLL2 generates the horizontal and vertical timing,
e.g. blanking, clamping and composite sync. Phase
and frequency are synchronized by the front sync
– PLL3 adjusts the phase of the horizontal drive pulse
and compensates for the delay of the horizontal output
stage. Phase and frequency are synchronized
by the oscillator signal of PLL2.
The horizontal drive circuitry uses a digital sine wave
generator to produce the exact (subclock) timing for
the drive pulse HOUT. The generator runs at 1 MHz.
Under control of the EHPLL bit and the internal voltage
supervision it is either synchronized by the deflection
PLL or it is free running. In the output stage the frequency
is divided down to give drive-pulse period and
width. The drive pulse width is programmable. The
horizontal drive uses an open drain output transistor.
After power on or during reset the HOUT generation is
switched to a free running mode with a fix duty cycle of
50%. For normal operation the EHPLL bit has to be set
first. During the switch the actual period of HOUT can
vary by up to 1 µs.
2.11.2. Angle and Bow Correction
The Angle and Bow correction is part of the horizontal
drive PLL. This feature allows a shift of the horizontal
drive pulse phase depending on the vertical position
on the screen. The phase correction has a linear
(angle) and a quadratic term (bow).
2.11.3. Horizontal Phase Adjustment
This section describes a simple way to align PLL
phases and the horizontal frame position.
1. With HDRV the duration of the horizontal drive pulse
has to be adjusted
2. With POFS2 the delay between input video and display
timing (e.g. clamping pulse for analog RGB)
has to be adjusted
3. With CSYDEL the delay between video and analog
RGB (OSD) has to be adjusted.
4. With CSYDEL and HPOS the horizontal position of
both, the digital and analog RGB signal (from
SCART) relative to the clamping pulse has to be
adjusted to the correct position, e.g. the pedestal of
the generator signal.
5. With POFS3 the position of horizontal drive/flyback
relative to RGB has to be adjusted
6. With NEWLIN the position of a scaled video picture
can be adjusted (left, middle, center, etc; versions
with panorama scaler only).
7. With HBST and HBSO, the start and stop values for
the horizontal blanking have to be adjusted.
Note: The processing delay of the internal digital video
path differs depending on the comb filter option of the
VCT 38xxA/B. The versions with comb filter have an
additional delay of 34 clock cycles.
Vertical and East/West Deflection
The calculations of the vertical and East/West deflection
waveforms is done by the internal Fast Processor
(FP). The algorithm uses a chain of accumulators to
generate the required polynomial waveforms. To produce
the deflection waveforms, the accumulators are
initialized at the beginning of each field. The initialization
values must be computed by the TV control processor
and are written to the front-end once. The
waveforms are described as polynomials in x, where x
varies from 0 to 1 for one field.
P: a + b(x-0.5) + c(x-0.5)2 + d(x-0.5)3 + e(x-0.5)4
The initialization values for the accumulators a0..a3 for
vertical deflection and a0..a4 for East/West deflection
are 12-bit values.
Fig. 2–25 shows several vertical and East/West deflection
waveforms. The polynomial coefficients are also
In order to get a faster vertical retrace timing, the output
impedance of the vertical D/A-converter can be
reduced by 50% during the retrace.
2.11.5. EHT Compensation
The vertical waveform can be scaled according to the
average beam current. This is used to compensate the
effects of electric high-tension changes due to beam
current variations. EHT compensation for East/West
deflection is done with an offset corresponding to the
average beam current.
2.11.6. Protection Circuitry
Picture tube and drive stage protection is provided
through the following measures:
– Vertical flyback protection input:
This pin searches for a negative edge in every field,
otherwise the RGB drive signals are blanked.
– Drive shutoff during flyback:
This feature can be selected by software.
– Safety input pin:
This input has two thresholds. Between zero and
the lower threshold, normal functioning takes place.
Between the lower and the higher threshold, the
RGB signals are blanked. Above the higher threshold,
the RGB signals are blanked and the horizontal
drive is shut off. Both thresholds have a small hysteresis.
2.12. Reset Function
Reset of all VDP functions is performed by the RESQ
pin. When this pin becomes active, all internal registers
and counters are lost. The TV controller can activate
the RESQ pin by software (see Section 5.7.2. on
When the RESQ pin is released, the internal reset is
still active for 4 µs. After that time, the initialization of
all required registers is performed by the internal Fast
Processor. This takes approximately 60 µs. During this
initialization procedure it is not possible to access the
VDP via the I2C interface.
The VDP voltage supervision activates an internal
reset signal when the supply for the digital circuits
(VSUPD) goes below ~2.5 V for more than 50 ns.
2.14. I2C Bus Slave Interface
Communication between the video processing part of
the VDP and the CPU is done via I2C bus. For detailed
information on the I2C bus please refer to the Philips
manual ‘I2C bus Specification’.
The VDP has two I2C bus slave interfaces (for compatibility
with VPC/DDP applications) − one in the
front-end and one in the back-end. Both I2C bus interfaces
use I2C clock synchronization to slow down the
interface if required. Both I2C bus interfaces use one
level of subaddress: the I2C bus chip address is used
to address the VDP and a subaddress selects one of
the internal registers. The I2C bus chip addresses are
The registers of the VDP have 8 or 16-bit data size;
16-bit registers are accessed by reading/writing two
8-bit data words.
Fig. 2–26 shows I2C bus protocols for read and write
operations of the interface; the read operation requires
an extra start condition and repetition of the chip
address with read command set.
2.14.1. Control and Status Registers
Table 2–3 gives definitions of the VDP control and status
registers. The number of bits indicated for each
register in the table is the number of bits implemented
in hardware, i.e. a 9-bit register must always be
accessed using two data bytes but the 7 MSB will be
‘don’t care’ on write operations and ‘0’ on read operations.
Write registers that can be read back are indicated
in Table 2–3.
Functions implemented by software in the on-chip control
microprocessor (FP) are explained in Table 2–7.
A hardware reset initializes all control registers to 0.
The automatic chip initialization loads a selected set of
registers with the default values given in Table 2–3.
The register modes given in Table 2–3 are
– w: write only register
– w/r: write/read data register
– r: read data from VDP
– v: register is latched with vertical sync
– h: register is latched with horizontal
3. Text and OSD Processing
The VCT 38xxA/B includes a World System Teletext
(WST) decoder, whose display capabilities are also
used for OSD generation. In the following sections the
text and OSD processing part of the VCT 38xxA/B will
be named TPU for short.
With integrated CPU, RAM and ROM, an adaptive
data slicer, a display controller, and a number of interfaces,
the TPU offers acquisition and display of various
teletext and data services such as WST, PDC, VPS,
and WSS. Fig. 3–1 shows the functional block diagram
of the TPU.
The TPU operates independently from the TV controller
and can be controlled by software via I2C bus interface
(see Section 3.14. on page 85). The TV controller
is not burdened with the task of teletext decoding
and communicates with the TPU via a high-level command
The TPU performs the following tasks:
– teletext data acquisition (hardware)
– teletext data decoding (software)
– page generation (software)
– page memory management (software)
– page display (hardware)
– user interface (software)
3.2. SRAM Interface
The SRAM interface connects a standard SRAM to the
internal bus structure. The address bus is 19 bit wide,
addressing SRAMs up to 4 Mbit. Smaller SRAMs can
also be connected.
The SRAM interface has to handle 3 asynchronous
data streams. The CPU needs access to every memory
location of the SRAM. During VBI the slicer writes
up to 22 teletext lines of 43 Bytes into the acquisition
scratch memory. During text display the display controller
copies teletext rows from display memory into its
internal row buffer.
On VCT 38xxA/B the SRAM interface of the TPU is
connected to the memory bus of the TV controller. This
is done to save pins and to give the TV controller faster
access to the display memory. Refer to DMA Interface
(chapter 5.9. on page 101) for more details.
After reset the TPU will not use the SRAM interface
until receiving the I2C command “DRAM_MODE” (see
Section 3.12. on page 70).
3.3. Text Controller
The TPU operates with its own 65C02 core running at
10.125 MHz. The core can address up to 64 kBytes of
The CPU memory contains 640 Bytes RAM, 12 kBytes
program ROM and 12 kBytes character ROM. The
VCT 38xxB contains additional 12kBytes character
ROM. The character ROM holds the font data and is
separated from the program ROM to save CPU time.
The CPU can still access the character ROM via a
DMA interface including wait cycles. The display controller
can also access the CPU memory via the same
DMA interface. By this means it is possible to locate
part of the character font in program ROM or part of
the program code in character ROM.
After Reset the CPU switches to external font memory
if the Font ID vector exists in the external font memory.
After Reset the CPU switches to external program
memory if the Prog ID vector exists in the external program
3.4. Teletext Acquisition
The only task of the slicer circuit is to extract teletext
lines from the incoming composite video signal and to
store them into the acquisition scratch buffer of the
internal/external SRAM. No page selection is done at
this hardware level.
Four analog sources can be connected, thus it is possible
to receive text from one channel while watching
another on the screen. After clamping and AGC amplifier
the analog video signal is converted into binary
data. Sync separation is done by a sync slicer and a
horizontal PLL, which generate the horizontal and vertical
timing. By these means, no external sync signals
are needed and any available signal source can be
used for teletext reception.
The teletext information itself is acquired using adaptive
slicers on bit and byte level with soft error detection
to decrease the bit error rate under bad reception
conditions. The slicer can be programmed to different
bit rates for reception of PAL, NTSC or MAC world
system teletext as well as VPS, WSS, or CAPTION
3.5. Teletext Page Management
As a state-of-the-art teletext decoder, the TPU is able
to store and manage a sufficient number of teletext
pages to absorb the annoying transmission cycle
times. The number of available pages is only limited by
the memory size. With an intelligent software and a
4-Mbit SRAM it is possible to store and to control more
than 500 teletext pages.
The management of such a data base is a typical software
task and is therefore performed by the 65C02.
Using a fixed length page table with one entry for
every possible page, the software distributes the content
of the acquisition scratch buffer among the page
memory. The page size is fixed to 1 kByte, only ghost
rows are chained in 128-Byte segments to avoid
unused memory space.
A stored teletext page cannot be displayed directly,
because of the row-adaptive transmission and the
level 2 enhancements (row 26−29). Therefore, the
CPU has to transfer the selected teletext page into a
display page buffer, adding extra data such as character
set extension and non-spacing attributes.
3.5.1. Memory Manager
The Memory manager is the core of the internal TPU
firmware. Most of the acquisition and display related
functions are controlled by this management.
MSP3400CMultistandard Sound Processor
Release Notes: The hardware description in this
document is valid for the MSP 3400C – C8 and newer
codes. Revision bars indicate significant changes
to the previous version.
The MSP 3400C is designed as single-chip Multistandard
Sound Processor for applications in analog and
digital TV sets, satellite receivers and video recorders.
The MSP-family, which is based on the MSP 2400, demonstrates
the progressive development towards highly
integrated multi-functional ICs.
The MSP 3400C, again, improves function integration:
The full TV sound processing, starting with analog
sound IF signal-in, down to processed analog AF-out, is
performed in a single chip. The IC is produced in 0.8 mm
CMOS technology, combined with high performance
digital signal processing.
The MSP 3400C 0.8 m CMOS version is fully pin and
software compatible to the 1.0 m MSP 3400 and MSP
3410. The main difference between the MSP 3400C and
the MSP 3410, consists of the MSP 3410 being able to
decode NICAM signals.
2. Features of the MSP 3400C:
2.1. Features of the Demodulator and Decoder
The MSP 3400C is designed to perform demodulation
of FM-mono TV sound and two carrier FM systems according
to the German or Korean terrestrial specs. With
certain constraints, it is also possible to do AM-demodulation
according to the SECAM system. Alternatively, the
satellite specs can be processed with the MSP 3400C.
For FM carrier detection in satellite operation, the AMdemodulation
offers a powerful feature to calculate the
carrier field strength, which can be used for automatic
search algorithms. So, the IC facilitates a first step towards
multistandard capability with its very flexible
application and may be used in TV-sets, satellite tuners,
and video recorders.
The MSP 3400C facilitates profitable multistandard capability,
offering the following advantages:
– two selectable analog inputs (TV and SAT-IF sources)
– Automatic Gain Control (AGC) for analog input: input
range: 0.14 – 3 Vpp
– integrated A/D converter for sound-IF inputs
– all demodulation and filtering is performed on chip and
is individually programmable
– no external filter hardware is required
– only one crystal clock (18.432 MHz) is necessary
– FM carrier level calculation for automatic search algorithms
and carrier mute function
– high deviation FM-mono mode (max. deviation:
approx. 360 kHz)
2.2. Features of the DSP-Section
– flexible selection of audio sources to be processed
– digital input and output interfaces via I2S-Bus for external
DSP-processors, surround sound, ADR etc.
– digital interface to process ADR (Astra Digital Radio)
together with DRP 3510 A
– performance of all deemphasis systems including
adaptive Wegener Panda 1 without external components
– digitally performed FM-identification decoding and dematrixing
– digital baseband processing: volume, bass, treble,
5-band equalizer, loudness, pseudostereo, and basewidth
– simple controlling of volume, bass, treble, equalizer
– increased audio bandwidth for FM-Audio-signals
(20 Hz – 15 kHz, 1 dB)
2.3. Features of the Analog Section
– three selectable analog pairs of audio baseband inputs
(= three SCART inputs)
input level: 32 V RMS,
input impedance: .25 kW
– one selectable analog mono input (i.e. AM sound),
input level: 32 V RMS,
input impedance: .10 kW
– two high quality A/D converters, S/N-Ratio: .85 dB
– 20 Hz to 20 kHz Bandwidth for SCART-to-SCARTCopy
– MAIN (loudspeaker) and AUX (headphones): two
pairs of 4-fold oversampled D/A-converters
output level per channel: max. 1.4 V RMS
output resistance: max. 5 kW
S/N-Ratio: .85 dB at maximum volume
max. noise voltage in mute mode: 310 mV (BW: 20 Hz
– one pair of four-fold oversampled D/A-converters supplying
two selectable pairs of SCART-Outputs. Output
level per channel: max. 2 V RMS, output resistance:
max. 0.5 kW, S/N-Ratio: .85 dB
(20 Hz...16 kHz).
TDA9885; I2C-bus controlled single and multistandard alignment-free IF-PLL demodulatorsGENERAL DESCRIPTION
The TDA9885 is an alignment-free multistandard
(PAL and NTSC) vision and sound IF signal PLL
demodulator for negative modulation only and
The TDA9886 is an alignment-free multistandard
(PAL, SECAM and NTSC) vision and sound IF signal PLL
demodulator for positive and negative modulation,
including sound AM and FM processing.
· 5 V supply voltage
· Gain controlled wide-band Vision Intermediate
Frequency (VIF) amplifier, AC-coupled
· Multistandard true synchronous demodulation with
active carrier regeneration: very linear demodulation,
good intermodulation figures, reduced harmonics, and
excellent pulse response
· Gated phase detector for L and L-accent standard
· Fully integrated VIF Voltage Controlled Oscillator
(VCO), alignment-free, frequencies switchable for all
negative and positive modulated standards via I2C-bus
· Digital acquisition help, VIF frequencies of 33.4, 33.9,
38.0, 38.9, 45.75, and 58.75 MHz
· 4 MHz reference frequency input: signal from
Phase-Locked Loop (PLL) tuning system or operating
as crystal oscillator
· VIF Automatic Gain Control (AGC) detector for gain
control, operating as peak sync detector for negative
modulated signals and as a peak white detector for
positive modulated signals
· External AGC setting via pin OP1
· Precise fully digital Automatic Frequency Control (AFC)
detector with 4-bit digital-to-analog converter, AFC bits
readable via I2C-bus
· TakeOver Point (TOP) adjustable via I2C-bus or
alternatively with potentiometer
· Fully integrated sound carrier trap for 4.5, 5.5,
6.0, and 6.5 MHz, controlled by FM-PLL oscillator
· Sound IF (SIF) input for single reference Quasi Split
Sound (QSS) mode, PLL controlled
· SIF-AGC for gain controlled SIF amplifier, single
reference QSS mixer able to operate in high
performance single reference QSS mode and in
intercarrier mode, switchable via I2C-bus
· AM demodulator without extra reference circuit
· Alignment-free selective FM-PLL demodulator with high
linearity and low noise
· Four selectable I2C-bus addresses
· I2C-bus control for all functions
· I2C-bus transceiver with pin programmable Module
· TV, VTR, PC, and STB applications.
Figure 1 shows the simplified block diagram of the device
which comprises the following functional blocks:
· VIF amplifier
· Tuner AGC and VIF-AGC
· VIF-AGC detector
· Frequency Phase-Locked Loop (FPLL) detector
· VCO and divider
· AFC and digital acquisition help
· Video demodulator and amplifier
· Sound carrier trap
· SIF amplifier
· SIF-AGC detector
· Single reference QSS mixer
· AM demodulator
· FM demodulator and acquisition help
· Audio amplifier and mute time constant
· Internal voltage stabilizer
· I2C-bus transceiver and MAD (module address).
8.1 VIF amplifier
The VIF amplifier consists of three AC-coupled differential
stages. Gain control is performed by emitter degeneration.
The total gain control range is typically 66 dB. The
differential input impedance is typically 2 kWin parallel with
8.2 Tuner AGC and VIF-AGC
This block adapts the voltages, generated at the VIF-AGC
and SIF-AGC detectors, to the internal signal processing
at the VIF and SIF amplifiers and performs the tuner AGC
control current generation. The onset of the tuner AGC
control current generation can be set either via the I2C-bus
(see Table 13) or optionally by a potentiometer at pin TOP
(in case that the I2C-bus information cannot be stored,
related to the device). The presence of a potentiometer is
automatically detected and the I2C-bus setting is disabled.
Furthermore, derived from the AGC detector voltage, a
comparator is used to test if the corresponding VIF input
voltage is higher than 200 mV. This information can be
read out via the I2C-bus (bit VIFLEV = 1).
8.3 VIF-AGC detector
Gain control is performed by sync level detection (negative
modulation) or peak white detection (positive modulation).
For negative modulation, the sync level voltage is stored at
an integrated capacitor by means of a fast peak detector.
This voltage is compared with a reference voltage
(nominal sync level) by a comparator which charges or
discharges the integrated AGC capacitor for the
generation of the required VIF gain. The time constants for
decreasing or increasing the gain are nearly equal and the
total AGC reaction time is fast to cope with ‘aeroplane
For positive modulation, the white peak level voltage is
compared with a reference voltage (nominal white level)
by a comparator which charges (fast) or discharges (slow)
the external AGC capacitor directly for the generation of
the required VIF gain. The need of a very long time
constant for VIF gain increase is because the peak white
level may appear only once in a field. In order to reduce
this time constant, an additional level detector increases
the discharging current of the AGC capacitor (fast mode)
in the event of a decreasing VIF amplitude step controlled
by the detected actual black level voltage. The threshold
level for fast mode AGC is typically -6 dB video amplitude.
The fast mode state is also transferred to the SIF-AGC
detector for speed-up. In case of missing peak white
pulses, the VIF gain increase is limited to typically +3 dB
by comparing the detected actual black level voltage with
a corresponding reference voltage.
8.4 FPLL detector
The VIF amplifier output signal is fed into a frequency
detector and into a phase detector via a limiting amplifier
for removing the video AM.
During acquisition the frequency detector produces a
current proportional to the frequency difference between
the VIF and the VCO signals. After frequency lock-in the
phase detector produces a current proportional to the
phase difference between the VIF and the VCO signals.
The currents from the frequency and phase detectors are
charged into the loop filter which controls the VIF VCO and
locks it to the frequency and phase of the VIF carrier.
For a positive modulated VIF signal, the charging currents
are gated by the composite sync in order to avoid signal
distortion in case of overmodulation. The gating depth is
switchable via the I2C-bus.
8.5 VCO and divider
The VCO of the VIF-FPLL operates as an integrated low
radiation relaxation oscillator at double the picture carrier
frequency. The control voltage, required to tune the VCO
to double the picture carrier frequency, is generated at the
loop filter by the frequency phase detector. The possible
frequency range is 50 to 140 MHz (typical value).
The oscillator frequency is divided-by-two to provide two
differential square wave signals with exactly 90 degrees
phase difference, independent of the frequency, for use in
the FPLL detectors, the video demodulator and the
8.6 AFC and digital acquisition help
Each relaxation oscillator of the VIF-PLL and FM-PLL
demodulator has a wide frequency range. To prevent false
locking of the PLLs and with respect to the catching range,
the digital acquisition help provides an individual control,
until the frequency of the VCO is within the preselected
standard dependent lock-in window of the PLL.
The in-window and out-window control at the FM-PLL is
additionally used to mute the audio stage (if auto mute is
selected via the I2C-bus).
The working principle of the digital acquisition help is as
follows. The PLL VCO output is connected to a down
counter which has a predefined start value (standard
dependent). The VCO frequency clocks the down counter
for a fixed gate time. Thereafter, the down counter stop
value is analysed. In case the stop value is higher (lower)
than the expected value range, the VCO frequency is
lower (higher) than the wanted lock-in window frequency
range. A positive (negative) control current is injected into
the PLL loop filter and consequently the VCO frequency is
increased (decreased) and a new counting cycle starts.
The gate time as well as the control logic of the acquisition
help circuit is dependent on the precision of the reference
signal at pin REF. Operation as a crystal oscillator is
possible as well as connecting this input via a serial
capacitor to an external reference frequency, e.g. the
tuning system oscillator.
The AFC signal is derived from the corresponding down
counter stop value after a counting cycle. The last four bits
are latched and can be read out via the I2C-bus
(see Table 7). Also the digital-to-analog converted value is
given as current at pin AFC.
8.7 Video demodulator and amplifier
The video demodulator is realized by a multiplier which is
designed for low distortion and large bandwidth. The VIF
signal is multiplied with the ‘in phase’ signal of the VIF-PLL
The demodulator output signal is fed into the video
preamplifier via a level shift stage with integrated low-pass
filter to achieve carrier harmonics attenuation.
The output signal of the preamplifier is fed to the VIF-AGC
detector (see Section 8.3) and in the sound trap mode also
fed internally to the integrated sound carrier trap
(see Section 8.8). The differential trap output signal is
converted and amplified by the following postamplifier.
The video output level at pin CVBS is 2 V (p-p).
In the bypass mode the output signal of the preamplifier is
fed directly through the postamplifier to pin CVBS. The
output video level is 1.1 V (p-p) for using an external sound
trap with 10 % overall loss.
Noise clipping is provided in both cases.
8.8 Sound carrier trap
The sound carrier trap consists of a reference filter, a
phase detector and the sound trap itself.
A sound carrier reference signal is fed into the reference
low-pass filter and is shifted by nominal 90 degrees. The
phase detector compares the original reference signal with
the signal shifted by the reference filter and produces a
DC voltage by charging or discharging an integrated
capacitor with a current proportional to the phase
difference between both signals, respectively to the
frequency error of the integrated filters. The DC voltage
controls the frequency position of the reference filter and
the sound trap. So the accurate frequency position for the
different standards is set by the sound carrier reference
The sound trap itself is constructed of three separate traps
to realize sufficient suppression of the first and second
8.9 SIF amplifier
The SIF amplifier consists of three AC-coupled differential
stages. Gain control is performed by emitter degeneration.
The total gain control range is typically 66 dB. The
differential input impedance is typically 2 kWin parallel with
8.10 SIF-AGC detector
SIF gain control is performed by the detection of the
DC component of the AM demodulator output signal. This
DC signal corresponds directly to the SIF voltage at the
output of the SIF amplifier so that a constant SIF signal is
supplied to the AM demodulator and to the single
reference QSS mixer.
By switching the gain of the input amplifier of the SIF-AGC
detector via the I2C-bus, the internal SIF level for
FM sound is 5.5 dB lower than for AM sound. This is to
adapt the SIF-AGC characteristic to the VIF-AGC
characteristic. The adaption is ideal for a picture-to-sound
FM carrier ratio of 13 dB.
Via a comparator, the integrated AGC capacitor is charged
or discharged for the generation of the required SIF gain.
Due to AM sound, the AGC reaction time is slow
(fc < 20 Hz for the closed AGC loop). For reducing this
AM sound time constant in the event of a decreasing
IF amplitude step, the load current of the AGC capacitor is
increased (fast mode) when the VIF-AGC detector (at
positive modulation mode) operates in the fast mode too.
An additional circuit (threshold approximately 7 dB)
ensures a very fast gain reduction for a large increasing
IF amplitude step.
8.11 Single reference QSS mixer
With the present system a high performance Hi-Fi stereo
sound processing can be achieved. For a simplified
application without a SIF SAW filter, the single reference
QSS mixer can be switched to the intercarrier mode via the
The single reference QSS mixer generates the 2nd FM
TV sound intercarrier signal. It is realized by a linear
multiplier which multiplies the SIF amplifier output signal
and the VIF-PLL VCO signal (90 degrees output) which is
locked to the picture carrier. In this way the QSS mixer
operates as a quadrature mixer in the intercarrier mode
and provides suppression of the low frequency video
The QSS mixer output signal is fed internally via a
high-pass and low-pass combination to the
FM demodulator as well as via an operational amplifier to
the intercarrier output pin SIOMAD.
8.12 AM demodulator
The amplitude modulated SIF amplifier output signal is fed
both to a two-stage limiting amplifier that removes the AM
and to a linear multiplier. The result of the multiplication of
the SIF signal with the limiter output signal is
AM demodulation (passive synchronous demodulator).
The demodulator output signal is fed via a low-pass filter
that attenuates the carrier harmonics and via the input
amplifier of the SIF-AGC detector to the audio amplifier.
8.13 FM demodulator and acquisition help
The narrow-band FM-PLL detector consists of:
· Gain controlled FM amplifier and AGC detector
· Narrow-band PLL.
The intercarrier signal from the intercarrier mixer is fed to
the input of an AC-coupled gain controlled amplifier with
two stages. The gain controlled output signal is fed to the
phase detector of the narrow-band FM-PLL
(FM demodulator). For good selectivity and robustness
against disturbance caused by the video signal, a high
linearity of the gain controlled FM amplifier and of the
phase detector as well as a constant signal level are
required. The gain control is done by means of an ‘in
phase’ demodulator for the FM carrier (from the output of
the FM amplifier). The demodulation output is fed into a
comparator for charging or discharging the integrated
AGC capacitor. This leads to a mean value AGC loop to
control the gain of the FM amplifier.
The FM demodulator is realized as a narrow-band PLL
with an external loop filter, which provides the necessary
selectivity (bandwidth approximately 100 kHz). To achieve
good selectivity, a linear phase detector and a constant
input level are required. The gain controlled intercarrier
signal from the FM amplifier is fed to the phase detector.
The phase detector controls via the loop filter the
integrated low radiation relaxation oscillator. The designed
frequency range is from 4 to 7 MHz.
The VCO within the FM-PLL is phase-locked to the
incoming 2nd SIF signal, which is frequency modulated.
As well as this, the VCO control voltage is superimposed
by the AF voltage. Therefore, the VCO tracks with the FM
of the 2nd SIF signal. So, the AF voltage is present at the
loop filter and is typically 5 mV (RMS) for 27 kHz
FM deviation. This AF signal is fed via a buffer to the audio
The correct locking of the PLL is supported by the digital
acquisition help circuit.
8.14 Audio amplifier and mute time constant
The audio amplifier consists of two parts:
· AF preamplifier
· AF output amplifier.
The AF preamplifier used for FM sound is an operational
amplifier with internal feedback, high gain and high
common mode rejection. The AF voltage from the
PLL demodulator is 5 mV (RMS) for a frequency deviation
of 27 kHz and is amplified by 30 dB. By the use of a
DC operating point control circuit (with external
capacitor CAF), the AF preamplifier is decoupled from the
PLL DC voltage. The low-pass characteristic of the
amplifier reduces the harmonics of the sound intercarrier
signal at the AF output terminal.
For FM sound a switchable de-emphasis network (with
external capacitor) is implemented between the
preamplifier and the output amplifier.
The AF output amplifier provides the required AF output
level by a rail-to-rail output stage. A preceding stage
makes use of an input selector for switching between
FM sound, AM sound and mute state. The gain can be
switched between 10 dB (normal) and 4 dB (reduced).
Switching to the mute state is controlled automatically,
dependent on the digital acquisition help in case the VCO
of the FM-PLL is not in the required frequency window.
This is done by a time constant: fast for switching to the
mute state and slow (typically 40 ms) for switching to the
All switching functions are controlled via the I2C-bus:
· AM sound, FM sound and forced mute
· Auto mute enable or disable
· De-emphasis off or on with 50 or 75 ms
· Audio gain normal or reduced.
8.15 Internal voltage stabilizer
The band gap circuit internally generates a voltage of
approximately 2.4 V, independent of supply voltage and
temperature. A voltage regulator circuit, connected to this
voltage, produces a constant voltage of 3.55 V which is
used as an internal reference voltage.
8.16 I2C-bus transceiver and module address
The device can be controlled via the 2-wire I2C-bus by a
microcontroller. Two wires carry serial data (SDA) and
serial clock (SCL) information between the devices
connected to the I2C-bus.
The device has an I2C-bus slave transceiver with
auto-increment. The circuit operates up to clock
frequencies of 400 kHz.
A slave address is sent from the master to the slave
receiver. To avoid conflicts in a real application with other
devices providing similar or complementing functions,
there are four possible slave addresses available. These
Module Addresses (MADs) can be selected by connecting
resistors on pin SIOMAD and/or pins SIF1 and SIF2 (see
Fig.23). Pin SIOMAD relates with bit A0 and pins SIF1
and SIF2 relate with bit A3. The slave addresses of this
device are given in Table 1.
The power-on preset value is dependent on the use of
pin SIOMAD and can be chosen for 45.75 MHz NTSC as
default (pin SIOMAD left open-circuit) or 58.75 MHz NTSC
(resistor on pin SIOMAD). In this way the device can be
used without the I2C-bus as an NTSC only device.
Remark: In case of using the device without the I2C-bus,
then the rise time of the supply voltage after switching on
power must be longer than 1.2 ms.
TDA7480 10W MONO CLASS-D AMPLIFIER
The TDA7480 is an audio class-D amplifier assembled
in Power DIP package specially designed
for high efficiency applications mainly for
TV and Home Stereo sets.
10W OUTPUT POWER:
RL = 8W/4W; THD = 10%
ST-BY AND MUTE FEATURES
SHORT CIRCUIT PROTECTION
THERMAL OVERLOAD PROTECTION
DESOR H J: "SINGLE-CHIP VIDEO PROCESSING SYSTEM" IEEE TRANSACTIONS ON CONSUMER ELECTRONICS, IEEE INC. NEW YORK, US, vol. 37, no. 3, 1 August 1991 (1991-08-01), pages 182-189, XP000263183 ISSN: 0098-3063
BOLTON M: "EMPFÄNGER-IC FÜR DIGITALES FERNSEHEN" ELEKTRONIK INDUSTRIE, vol. 25, no. 8, August 1994 (1994-08), pages 60,62-63, XP000560093
HING-YIP TONG: "A SINGLE CHIP MICRO-COMPUTER FOR A/V MONITOR AND TV RECEIVER" IEEE TRANSACTIONS ON CONSUMER ELECTRONICS, IEEE INC. NEW YORK, US, vol. 36, no. 4, 1 November 1990 (1990-11-01), pages 825-831, XP000178986 ISSN: 0098-3063
MURAYAMA A ET AL: "SINGLE-CHIP BICMOS MULTISTANDARD VIDEO PROCESSOR" IEEE TRANSACTIONS ON CONSUMER ELECTRONICS, IEEE INC. NEW YORK, US, vol. 42, no. 3, August 1996 (1996-08), pages 739-748, XP000638562 ISSN: 0098-3063
NEDERLOF L: "ONE-CHIP TV" IEEE INTERNATIONAL SOLID STATE CIRCUITS CONFERENCE, IEEE SERVICE CENTER, NEW YORK, NY, US, vol. 39, February 1996 (1996-02), pages 26-29, XP000685525 ISSN: 0193-6530
GASS W: "ARCHITECTURE TRENDS OF MPEG DECODERS FOR SET-TOP BOX" PROCEEDINGS OF THE SPIE, SPIE, BELLINGHAM, VA, US, vol. 3021, 12 February 1997 (1997-02-12), pages 162-169, XP000648211 ISSN: 0277-786X
DROITCOURT J-L: "Integra architecture-anatomy of the interactive television set-top box, how it works, and what it means to the consumer" BROADCASTING CONVENTION, INTERNATIONAL (CONF. PUBL. NO. 428) AMSTERDAM, NETHERLANDS 12-16 SEPT. 1996, LONDON, UK,IEE, UK, 12 September 1996 (1996-09-12), pages 272-276, XP006510031 ISBN: 0-85296-663-6
PERKINS G W ET AL: "A MULTI MODE HIGH DEFINITION AND PERSONAL COMPUTER DISPLAY CHIP SET" PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON CONSUMER ELECTRONICS. (ICCE). ROSEMONT, ILL., JUNE 6 - 8, 1990, NEW YORK, IEEE, US, vol. CONF. 9, 6 June 1990 (1990-06-06), pages 220-221, XP000169826