TDA7350A_05 Datasheet, PDF (10/23 Pages) STMicroelectronics – 22W BRIDGE-STEREO AMPLIFIER FOR CAR RADIO

TDA7350A
4.3 Delayed Turn-on (muting)
The CSVR sets a signal turn-on delay too. A circuit is included which mutes the device until the voltage
on SVR pin reaches ~2.5V typ (fig. 28). The mute function is obtained by duplicating the input differential
pair (fig. 29): it can be switched to the signal source or to an internal mute input. This feature is necessary
to prevent transients at the inputs reaching the loudspeaker(s) immediately after power-on).
Fig. 28 represents the detailed turn-on transient with reference to the stereo configuration. At the power-
on the output decoupling capacitors are charged through an internal path but the device itself remains
switched off (Phase 1 of the represented diagram).
When the outputs reach the voltage level of about 1V (this means that there is no presence of short cir-
cuits) the device switches on, the SVR capacitor starts charging itself and the output tracks exactly the
SVR pin.
During this phase the device is muted until the SVR reaches the "Play" threshold (~2.5V typ.), after that
the music signal starts being played.
4.4 Stereo/Bridge Switching
There is also no need for external components for changing from stereo to bridge configuration (figg. 27-
30). A simple short circuit between two pins allows phase reversal at one output, yet maintaining the qui-
escent output voltage.
4.5 Stand-by
The device is also equipped with a stand-by function, so that a low current, and hence low cost switch,
can be used for turn on/off.
4.6 Stability
The device is provided with an internal compensation wich allows to reach low values of closed loop gain.
In this way better performances on S/N ratio and SVR can be obtained.
Figure 27. Block Diagram; Stereo Configuration
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