Diagnostics functional description

TDA7575B

24/32

Figure 31.

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 32.

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 33.

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 34.

Load detection thresholds - high gain setting

Bias (power amp turn-on)

permitted time

Turn-on diagnostic

acquisition time (100mS Typ)

t

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

D02AU1341

S.C. to GND

x

S.C. to Vs

0V

1.8V

x

Normal Operation

1.2V

S.C. across Load

x

Open Load

0V

1.5

Ω

70

Ω

Infinite

x

Normal Operation

0.5

Ω

130

Ω

D01AU1254

D01AU1252

S.C. across Load

x

Open Load

0

Ω

4.5

Ω

200

Ω

infinite

x

Normal Operation

1.5

Ω

400

Ω