TDA7564B datasheet(14/34 Pages) STMICROELECTRONICS

14 / 34 page

Diagnostics functional description

TDA7564B

14/34

Diagnostics functional description

4.1

Turn-on diagnostic

It is activated at the turn-on (stand-by out) under 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 are in place, a subsonic (inaudible) current

pulse (Figure 19) 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 "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 19. Turn - on diagnostic: working principle

Figure 20 and 21 show SVR and OUTPUT waveforms at the turn-on (stand-by out) with and

without turn-on diagnostic.

Figure 20. 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)

Diagnostic Enable

(Permanent)

Permanent diagnostic

acquisition time (100mS Typ)

Permanent Diagnostics data (output)

permitted time

I2CB DATA

Vsvr

Out

FAULT

event

Read Data

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