TDA7575B

Diagnostics functional description

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7

Diagnostics functional description

7.1

Turn-on diagnostic

–

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 (Figure 29) 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

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 29.

Turn - on diagnostic: working principle

Fig. Figure 30 and Figure 31 show SVR and OUTPUT waveforms at the turn-on (stand-by

out) with and without Turn-on diagnostic.

Figure 30.

SVR and output behavior - 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