TDA7577BLVPD datasheet(17/43 Pages) STMICROELECTRONICS

17 / 43 page

DocID025375 Rev 5

17/43

TDA7577BLV

Diagnostics functional description

4.1

Turn-on diagnostic

It is strongly recommended to activate this function at the turn-on (standby out) through I2C

bus 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 is in place, a subsonic (inaudible) current pulse

(Figure 23) is internally generated, sent through the speaker(s) and sunk back. The Turn-on

diagnostic status is internally stored until a successive diagnostic pulse is requested (after a

I2C reading).

If the "standby out" and "diag. enable" commands are both given through a single

programming step, the pulse takes place first (during the pulse power stages stay off,

showing high impedance at the outputs).

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 23. Turn-on diagnostic: working principle

Fig. Figure 24 and Figure 25 show SVR and OUTPUT waveforms at the turn-on (standby

out) with and without turn-on diagnostic.

Figure 24. SVR and output behavior - case 1: without turn-on diagnostic

TDA7577BLVPD Datasheet(PDF) 17 Page - STMicroelectronics