TDA7566_10 Datasheet, PDF (12/29 Pages) STMicroelectronics – 4 x 40 W multifunction quad power amplifier with built-in diagnostics features

Diagnostics functional description
4
Diagnostics functional description
TDA7566
4.1
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 V_S
– Short across the speaker
– Open speaker
To verify if any of the above misconnections are in place, a subsonic (inaudible) current
pulse (Figure 16) 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 "diag. 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 16. Turn-on diagnostic: working principle
Vs~5V
Isource
Isink
CH+
CH-
I (mA)
Isource
Isink
~100ms
Measure time
t (ms)
Figure 17 and 18 show SVR and output waveforms at the turn-on (standby out) with and
without Turn-on diagnostic.
12/29
Doc ID 9801Rev 5