Application hints

TDA7560A

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3

Application hints

(ref. to the circuit of Figure 3)

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 TDA7560A'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 (0.1µF) is adopted, the low frequency cut-off

will amount to 16 Hz.

3.3

Standby and muting

Standby and Muting facilities are both CMOS-compatible. In absence of true CMOS ports or

microprocessors, a direct connection to Vs of these two pins is admissible but a 470 kOhm

equivalent resistance should be present between the power supply and the muting and

ST-BY pins.

R-C cells have always to be used in order to smooth down the transitions for preventing any

audible transient noises.

About the standby, the time constant to be assigned in order to obtain a virtually pop-free

transition has to be slower than 2.5 V/ms.

3.4

DC offset detector

The TDA7560A integrates a DC offset detector to avoid that an anomalous DC offset on the

inputs of the amplifier may be multiplied by the gain and result in a dangerous large offset on

the outputs which may lead to speakers damage for overheating. The feature is enabled by

the MUTE pin (according to Table 4) and works with the amplifier unmuted and with no

signal on the inputs.

The DC offset detection can be available at 2 different pins:

–

Pin 2 (always enabled)

–

Pin 26. Only enabled if Vmute (pin23) is set higher than 8V. If not (Vmute < 6 V)

pin 26 will revert to the original HSD function

3.5

Heatsink definition

Under normal usage (4 Ohm speakers) the heatsink's thermal requirements have to be

deduced from Figure 16, which reports the simulated power dissipation when real

music/speech programmes are played out. Noise with gaussian-distributed amplitude was

employed for this simulation. Based on that, frequent clipping occurrence (worst-case) will

heatsink's thermal resistance should be approximately 2 °C/W. This would avoid any

thermal shutdown occurrence even after long-term and full-volume operation