TDA7564B datasheet(15/34 Pages) STMICROELECTRONICS

15 / 34 page

TDA7564B

Diagnostics functional description

15/34

Figure 21. SVR and output pin behavior (case 2: with turn-on diagnostic)

The information related to the outputs status is read and memorized at the end of the

current pulse top. The acquisition time is 100 ms (typ.). No audible noise is generated in the

process. As for SHORT TO GND / Vs the fault-detection thresholds remain unchanged from

26 dB to 12 dB gain setting. They are as follows:

Figure 22. Short circuit detection thresholds

Concerning Short across the speaker / Open speaker, the threshold varies from 26 dB to 12

dB gain setting, since different loads are expected (either normal speaker's impedance or

high impedance). The values in case of 26 dB gain are as follows:

Figure 23. Load detection thresholds - high gain setting

If the Line-Driver mode (Gv= 12 dB and Line Driver Mode diagnostic = 1) is selected, the

same thresholds will change as follows:

Figure 24. Load detection threshold - low gain setting

Bias (power amp turn-on)

permitted time

Turn-on diagnostic

acquisition time (100mS Typ)

Read Data

Permanent diagnostic

acquisition time (100mS Typ)

Permanent Diagnostics data (output)

permitted time

Diagnostic Enable

(Turn-on)

Turn-on Diagnostics data (output)

permitted time

I2CB DATA

Vsvr

Out

Diagnostic Enable

(Permanent)

FAULT

event

D01AU1253

S.C. to GND

S.C. to Vs

1.8V

VS-1.8V

Normal Operation

1.2V

VS-1.2V

S.C. across Load

Open Load

1.5

Infinite

Normal Operation

0.5

AC00060

D02AU1340

S.C. across Load

Open Load

180

infinite

Normal Operation

330

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