Diagnostics functional description

TDA7567PD

12/30

Doc ID 16903 Rev 2

3

Diagnostics functional description

3.1

Turn-on diagnostic

It is activated at the turn-on (standby 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 5) 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 "standby out" and "diagnostic enable" commands are both given through a single

programming step, the pulse takes place first (power stage still in standby 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 5.

Turn-on diagnostic: working principle

Figure 6 and 7 show SVR and output waveforms at the turn-on (standby out) with and

without turn-on diagnostic.

Figure 6.

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