TDA7389 Datasheet, PDF (11/14 Pages) STMicroelectronics – 4 x 45W quad bridge car radio amplifier

TDA7389
3
Application hints
Application hints
Ref. to the circuit of Figure 14.
3.1
SVR
Besides its contribution to the ripple rejection, the SVR capacitor governs the turn ON/OFF
time sequence and, consequently, plays an essential role in the pop optimization during
ON/OFF transients.
To conveniently serve both needs, ITS MINIMUM RECOMMENDED VALUE IS 22µF, 47µF
can be used to optimize pop performances.
3.2
Input stage
The TDA7389’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.
The input capacitors should be 1/4 of the capacitor connected to AC-GND pin for optimum
pop performances.
3.3
Stand-by and Muting
Stand-by and Muting facilities are both 3.3V CMOS-COMPATIBLE. If unused, a straight
connection to V_s of their respective pins would be admissible.
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 10µA normally flows out of pin 23, the maximum allowable
muting-series 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 23 may rise
to above the 1.2V 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 assigned in order to obtain a virtually pop-free
transition has to be slower than 2.5V/ms.
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