TDA7575B Datasheet, PDF (24/32 Pages) STMicroelectronics – 2 x 75W multifunction dual-bridge power amplifier with integrated digital diagnostics

Diagnostics functional description
TDA7575B
Figure 31. SVR and output pin behavior - case 2: with turn-on diagnostic
Vsvr
Out
Turn-on diagnostic
acquisition time (100mS Typ)
Permanent diagnostic
acquisition time (100mS Typ)
t
Diagnostic Enable
(Turn-on)
Turn-on Diagnostics data (output)
permitted time
Diagnostic Enable
(Permanent)
FAULT
event
I2CB DATA
Bias (power amp turn-on)
permitted time
Read Data
Permanent Diagnostics data (output)
permitted time
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
S.C. to GND x Normal Operation x
S.C. to Vs
0V
1.2V 1.8V
V_S-1.5V V_S-0.9V
V_S
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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
S.C. across Load x Normal Operation x
Open Load
0V
0.5Ω 1.5Ω
70Ω
130Ω
Infinite
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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
S.C. across Load x Normal Operation x
Open Load
0Ω
1.5Ω 4.5Ω
200Ω 400Ω
infinite
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