TDA7854

Application hints

9/12

4

Application hints

4.1

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.

4.2

Input stage

The TDA7854'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 (0.1

μF) is adopted, the low frequency cut-off

will amount to 16 Hz.

4.3

Stand-by and muting

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

audible transient noise.

About 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.

A direct connection to Vs of these two pins is admissible but a 470kOhm equivalent

resistance should be present between the power supply and muting and stand-by pins.

4.4

Heatsink definition

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

deduced from Figure 4, 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.

Figure 4.

5

10

15

20

25

30

0123456

V

R

GAUSSIAN NOISE

CLIP START

P

P

AC00036