Application hints

TDA7388A

10/13

DocID14257 Rev 5

3

Application hints

Ref. to the circuit of Figure 2.

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 10 µF.

3.2

Input stage

The TDA7388A’s inputs are ground-compatible and can stand very high input signals

(± 8 Vpk) without any performances degradation.

If the standard value for the input capacitors (0.1 µF) is adopted, the low frequency cut-off

will amount to 16 Hz.

3.3

Standby and muting

Standby and muting facilities are both 3.3V CMOS-compatible. If unused, a straight

connection to VS 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 10 µA normally flows out of pin 23, the maximum allowable

muting-series resistance (R2) is 70 k, which is sufficiently high to permit a muting capacitor

reasonably small (about 1 µF).

If R2 is higher than recommended, the involved risk will be that the voltage at pin 23 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 assigned in order to obtain a virtually pop-free

transition has to be slower than 2.5 V/ms.