TDA7381(1999) 데이터 시트보기 (PDF) - STMicroelectronics
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TDA7381 Datasheet PDF : 10 Pages
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TDA7381
APPLICATION HINTS (ref. to the circuit of fig. 1)
BIASING AND SVR
As shown by fig. 3, all the TDA7381’s main sec-
tions, such as INPUTS, OUTPUTS AND AC-GND
(pin 16) are internally biased at half Supply Volt-
age level (Vs/2), which is derived from the Supply
Voltage Rejection (SVR) block. In this way no cur-
rent flows through the internal feedback network.
The AC-GND is common to all the 4 amplifiers
and represents the connection point of all the in-
verting inputs.
Both individual inputs and AC-GND are con-
nected to Vs/2 (SVR) by means of 100KΩ resis-
tors.
To ensure proper operation and high supply volt-
age rejection, it is of fundamental importance to
provide a good impedance matching between IN-
PUTS and AC-GROUND terminations. This im-
plies that C1, C2, C3, C4, C5 CAPACITORS HAVE
TO CARRY THE SAME NOMINAL VALUE AND
THEIR TOLERANCE SHOULD NEVER EXCEED
±10 %.
Besides its contribution to the ripple rejection, the
SVR capacitor governs the turn ON/OFF time se-
quence and, consequently, plays an essential role
in the pop optimization during ON/OFF transients.
To conveniently serve both needs, ITS MINIMUM
RECOMMENDED VALUE IS 10µF.
INPUT STAGE
The TDA7381’S inputs are ground-compatible
and can stand very high input signals (± 8Vpk)
without any performances degradation.
If the standard value for the input capacitors
(0.1µF) is adopted, the low frequency cut-off will
amount to 16 Hz.
STAND-BY AND MUTING
STAND-BY and MUTING facilities are both
CMOS-COMPATIBLE. If unused, a straight con-
nection to Vs of their respective pins would be ad-
missible. Conventional low-power transistors can
be employed to drive muting and stand-by pins in
absence of true CMOS ports or microprocessors.
R-C cells have always to be used in order to
smooth down the transitions for preventing any
audible transient noises.
Since a DC current of about 10 uA normally flows
out of pin 22, the maximum allowable muting-se-
ries resistance (R2) is 70KΩ, which is sufficiently
high to permit a muting capacitor reasonably
small (about 1µF).
If R2 is higher than recommended, the involved
risk will be that the voltage at pin 22 may rise to
above the 1.5 V threshold voltage and the device
will consequently fail to turn OFF when the mute
line is brought down.
About the stand-by, the time constant to be as-
signed in order to obtain a virtually pop-free tran-
sition has to be slower than 2.5V/ms.
DIAGNOSTICS FACILITY
The TDA7381 is equipped with a diagnostics cir-
cuitry able to detect the following events:
CLIPPING in the output stage
OVERHEATING (THERMAL SHUT-DOWN
proximity)
Figure 3: Input/OutputBiasing.
100KΩ
0.1µF
C1 ÷ C4
IN
+
-
8KΩ
400Ω
6/10
VS
10KΩ
70KΩ SVR
10KΩ
100KΩ
47µF
C6
400Ω
8KΩ
-
AC_GND +
0.1µF
C5
D95AU302
TOWARDS
OTHER CHANNELS
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