TDA7566

8/19

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

Fig. 15 and 16 show SVR and OUTPUT waveforms at the turn-on (stand-by out) with and without TURN-ON

DIAGNOSTIC.

Figure 15. SVR and Output behaviour (CASE 1: without turn-on diagnostic)

CH-

CH+

Isource

Vs~5V

Isink

t (ms)

I (mA)

Isink

Isource

~100ms

Measure time

Bias (power amp turn-on)

t

Diagnostic Enable

(Permanent)

Permanent diagnostic

acquisition time (100mS Typ)

Permanent Diagnostics data (output)

permitted time

I2CB DATA

Vsvr

Out

FAULT

event

Read Data