STV8203 ST Microelectronics, STV8203 Datasheet - Page 5

• Manufacturer Part Number: STV8203
• Description: MULTISTANDARD TV SOUND DEMODULATOR
• Manufacturer: ST Microelectronics

FUNCTIONAL DESCRIPTION
As can be seen from the block diagram, the input to
the demodulator section is selectable from one of
two I.F. sources via the I
is then passed through an AGC block, having a
range of 28dB, before being digitised in the
ADC unit. A single quartz crystal (suggestedvalue :
between 24.712MHzand 27MHz) is used for the all
thedigital processing,includingdemodulation,iden-
tification, control, filtering. This has the advantage
of a singleclock signalsource for the wholeIC which
eliminates problems of multiple clock. The single
clock can be chosen to minimize interference in the
TV IF and RF stages of the tuner system.
The demodulatorsystem can identify and demodu-
late all the standarddescribedin the Table1. There-
sult of the recognition is flagged up to the host
system via the I
In the case of NICAM transmissions, in the event
of a failure of the received signal or a degradation
of the bit error rate (BER) below a prescribed level,
the system will automaticallydefault to the reserve
sound transmission on mono FM or AM.
For FM demodulation, the discriminator can nor-
mallyhandle signals having 250kHz deviation.This
covers all European standards, and ensure an
optimized compromise for the signal to noise ratio
in one hand, and overmodulation in the other hand.
However, it is possible to extand the deviation
range up to 500kHz (I
cover requests of some broadcasters.
Fully automatic standard recognition and setting
can be achieve using simple routines.
Figure 1 : Audio Matrix
LI2(SCART2)
LI1(SCART1)
2
C bus communication system.
DAC
MIN
2
C programmable) in order to
2
2
2
2
C bus. The selected signal
MUTE
GAIN
6dB
S1
S2
MUTE
MUTE
Appropriate de-emphasis networks in the digital
domain are applied to the resulting demodulated
signals (50 s, J17), followed by dematrixing if re-
quired. The digital datastream is then passed
through 2 x 16bits DACs before the audio matrix.
All this first section is working at 3.3V thanks to an
integrated voltage regulator. In stand-by mode, the
voltage regulator pulls the voltage down to zero,
ensuring no power dissipation in this part.
An audio matrix allows the selection of inputs ap-
plied on the outputsSCART1, SCART2 and MONO
according to the diagram shown in Figure 1.
The ”MOUT” outputs either the signal L1, or R1 or
(L1+R1)/2. This allows to record the selected chan-
nel in mono mode, for example on the linear chan-
nel of a VCR simultanously with the stereo mode.
Maximum output swing is 1V
The audio matrix section has its own power supply
regulator, allowing to keep this part working even
when the rest is in stand-by mode. This achieves a
”THRU” mode from input ”SCART1” to output
”SCART2” andinput”SCART2” to output”SCART1”.
The maximum output swing of both SCART1 and
SCART2 is 2V
Remark : Circuit operation is possible with only a
single 5V supply. In this case, the AV
is connected to 5V. Maximum output swing is then
limited to 1V
ically added to the DAC output. In that case, the
resistor shown as R2 = 39 in the ApplicationDia-
gram (between Pin 8 and Pin 21) must be replace
by a short circuit to avoid clipping.
L1/R1
L2/R2
RMS
SELECTOR
(L1 + R1)/2
RMS
L1, R1,
and a 6dB attenuationis automat-
.
2
2
AO1(SCART1)
MOUT
AO2(SCART2)
RMS
.
CC
STV8203
supply pin
5/31