9
Circuit description new circuits
37
L7.3A
–
STEREO & SAP information
–
STEREO: {MONO C -> 1/2(L+R) and STEREO SC-> 1/
2(L-R)} and SAP:{second audio channel}
The sinlge FM-mono sound decoding will take place in IC7225-
E; see circuit diagram A4.
IC7312 (= AN7318S) in diagram A7 is an Automatic Volume
Correction (AVC) present. Automatic volume correction (AVC)
function provides a constant output level of -18dBFS for input
levels between 0dBFS and -24dBFS. In this way it is possible
to adjust different sound sources (eg Terrestric/SAT channels,
SCART) to equal volume level. The increased volume of
advertising is compensated as well. The volume correction
step width is quasi continuosly. The filter maximum is
performed with an attack time of 16ms and a programmable
decay time i.e 8,4,2 sec and 20ms
IC7311: TDA7057AQ in circuit diagram A7 is a 2X3W stereo
sound amplifier.
Figure 9-1
Vref
DEMAGNETIZATION
MANAGEMENT
CL 56532018/012
080695
reference
block
supply &
initialisation block
OSCILLATOR
THERMAL
SHUTDOWN
PWM
LATCH
Set
Reset
Dmax &
SOFT-START
CONTROL
UVLO1
Vcc enable
Iref
OVER
VOLTAGE
MANAGEMENT
BUFFER
V
C
OUTPUT V
PIN 3
GND
2
3
4
1
16
8
9
10
15
STAND-BY
(REDUCED
FREQUENCY)
12
FOLDBACK
UVLO2
Vcc enable
OVERVOLTAGE
PROTECTION
5
MC44603
18V
UVLO1
UVLO2
Vcc enable
Iref
Vref
CURRENT
SENSE
5
11
+
-
AMP
7
Iref
Iref
Vdemag out
Vref
Vcc
Vosc
Vcs out
DEMAGNETIZATION
DETECTION
SYNCHRONIZATION
INPUT V
PIN 10
C
T
R
F ST-BY
R
P ST-BY
FOLDBACK
INPUT
CURRENT
SENSE INPUT
V
PIN 7
SOFT START (Css) /
Dmax (R
D
max)
VOLTAGE MODE CONTROL
VOLTAGE
FEEDBACK
INPUT
Vref/2
E/A OUTPUT
V
CC
Vosc prot
B
C
D
A
BLOCK DIAGRAM MC44603P
Rref
13
14
Q
Verror
