TDA7335 Datasheet, PDF (7/20 Pages) STMicroelectronics – STEREO PREAMP AMS DOLBY B* NOISE REDUCTION PROCESSOR

TDA7335
ELECTRICAL CHARACTERISTICS (continued)
DOLBY SECTION
Symbol
Parameter
Test Condition
RDO
Dolby Output Impedance
(pin 13, 18)
S/H
Signal Handling
VS = 8V; THD = 1%
B DEC 1 Decode Out
f = 10KHz; VI = 0.4dB
B DEC 2 Decode Out
f = 500Hz; VI = -22.1dB
B DEC 3 Decode Out
f = 2KHz; VI = -18dB
B DEC 4 Decode Out
f = 5KHz; VI = -29.7dB
B DEC 5 Decode Out
f = 10KHz; VI = -29.6dB
NRl
Dolby ONLow Level Pin20
NRh
Dolby OFF High Level Pin 20
GENERAL (PREAMPLIFIER + DOLBY)
DOLBY Min. Typ. Max. Unit
100 200 300 Ω
OFF 12
13
dB
ON -1.5 0
1.5 dB
ON -26.5 -25 -23.5 dB
ON -26.5 -25 -23.5 dB
ON -41.5 -40 -38.5 dB
ON -41.5 -40 -38.5 dB
0
0.8
V
2
VS
V
Symbol
THD
Parameter
Total Harmonic Dist.
S/N
Signal to Noise Ratio
C_S
Channel Separation
CT
Channel Cross Talk
Test Condition
VO = 0dB; f = 1KHz Dolby OFF
VO = 0dB; f = 1KHz Dolby ON
VO = 0dB; f = 10KHz Dolby OFF
VO = 0dB; f = 10KHz Dolby ON
Rg = 600Ω; VO = 0dB;
Unweighted; Dolby OFF
Rg = 600Ω; VO = 0dB;
Unweighted; Dolby ON
Rg = 600Ω; VO = 0dB;
CCIR/ARM; Dolby OFF
Rg = 600Ω; VO = 0dB;
CCIR/ARM; Dolby ON
Rg = 600Ω; f = 1KHz Dolby OFF
Rg = 600Ω; f = 1KHz Dolby ON
Rg = 600Ω; f = 1KHz Dolby OFF
Rg = 600Ω; f = 1KHz Dolby ON
Min.
54
56
50
56
Typ.
0.02
0.05
0.03
0.08
63
70
63
72
64
70
70
75
Max.
0.1
0.1
Unit
%
%
%
%
dB
dB
dB
dB
dB
dB
dB
dB
AUDIO MUSIC SENSOR (See Figure 2)
Aim of this section is to detect interprogram
spaces present on a recorded tape.
Both the blanks (interprogram spaces) and the
programs minimum detectable durations can be
easily set by means of 2 external and inde-
pendent time constants.
Also the minimum detectable input signal level
can be externally adjusted, by a dedicated gain
network.
Main blocks are:
Variable gain limiter amplifier
Signal detector circuitry
Logic blocks able to avoid unproperoperations.
Operations Description (refer to the simplified
schematic of Figure 2).
a)The two channels left and right mean signal
coming from the preamp chain (AC coupled)
are added (current) at the AMS input and pre-
sented to the limiter amplifier. The limiter am-
plifier gain is internally fixed to 40dB, and it
could be reduced by the R8 external resistor.
The AMSVth threshold is fixed at 1V. The fol-
lowing signal detector comparator informs of
the presence of music signal (High level out)
and avoids the erroneous detection of very
low signal (like noise) as real program.
b)The system moves in blank detection mode
everytime the supply is turned on or, with
power supplied, the AMS On/Off pin (to be
driven by an open collector output) is turned
off (T1 open). Once this condition has hap-
pened, the capacitor C15 charges, defining a
minimum reset time, long enough to reset the
Flip-Flops FF1 and FF2 and to descharge the
program detector external C7 capacitor. The
charging current at the AMS SW pin is about
10µA. It follows that the reset time (C15 x
Vpin8)/IC15 is given approximately by 0.122 x
C15 ns where C15 is in µF.
7/20