TDA7561

8/19

Figure 12. Power Dissipation vs. Average

Ouput Power (Audio Program

Simulation, 4

Ω)

Figure 13. Power Dissipation vs. Average

Ouput Power (Audio Program

Simulation, 2

Ω)

01

234

5

Po (W)

5

10

15

20

25

30

35

40

45

Ptot (W)

CLIP

START

Vs = 14.4 V

RL = 4x4 Ohm

GAUSSIAN NOISE

0123

45678

Po (W)

0

10

20

30

40

50

60

70

80

90

Ptot (W)

Vs = 14.4 V

RL = 4x2 Ohm

GAUSSIAN NOISE

CLIP

START

DIAGNOSTICS FUNCTIONAL DESCRIPTION:

a) TURN-ON DIAGNOSTIC.

It is activated at the turn-on (stand-by out) under I2Cbus request. Detectable output faults are:

- SHORT TO GND

- SHORT TO Vs

- SHORT ACROSS THE SPEAKER

- OPEN SPEAKER

To verify if any of the above misconnections are in place, a subsonic (inaudible) current pulse (fig. 14) is inter-

nally generated, sent through the speaker(s) and sunk back.The Turn On diagnostic status is internally stored

If the "stand-by out" and "diag. enable" commands are both given through a single programming step, the pulse

takes place first (power stage still in stand-by mode, low, outputs = high impedance).

Afterwards, when the Amplifier is biased, the PERMANENT diagnostic takes place. The previous Turn On state

is kept until a short appears at the outputs.

Figure 14. Turn - On diagnostic: working principle

CH-

CH+

Isource

Vs~5V

Isink

t (ms)

I (mA)

Isink

Isource

~100ms

Measure time