Philips CEM2000/00 Service Manual page 47

TDA7388
Figure 13. Output Noise vs. Source Figure 14. Power Dissipation & Efficiency vs.
Resistance. Output Power.
5 APPLICATION HINTS
(ref. to the circuit of fig. 4)
5.1 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 conve-
niently serve both needs, ITS MINIMUM RECOMMENDED VALUE IS 10µF.
5.2 INPUT STAGE
The TDA7388'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 fre-
quency cut-off will amount to 16 Hz.
5.3 STAND-BY AND MUTING
STAND-BY and MUTING facilities are both 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 22, the maximum allowable muting-series re-
sistance (R2) is 70KΩ, which is sufficiently high to permit a muting capacitor reasonably small (about 1µF).
If R is higher than recommended, the involved risk will be that the voltage at pin 22 may rise to above the
2
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 2.5V/ms.
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