TDA7566 Datasheet, PDF (8/19 Pages) STMicroelectronics – MULTIFUNCTION QUAD POWER AMPLIFIER WITH BUILT-IN DIAGNOSTICS FEATURES

TDA7566
DIAGNOSTICS FUNCTIONAL DESCRIPTION:
a) TURN-ON DIAGNOSTIC.
It is activated at the turn-on (stand-by out) under I2Cbus 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 (fig. 14) is inter-
nally 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 14. Turn - On diagnostic: working principle
Vs~5V
Isource
I (mA)
Isource
CH+
CH-
Isink
Isink
~100ms
Measure time
t (ms)
Fig. 15 and 16 show SVR and OUTPUT waveforms at the turn-on (stand-by out) with and without TURN-ON
DIAGNOSTIC.
Figure 15. SVR and Output behaviour (CASE 1: without turn-on diagnostic)
Vsvr
Out
Permanent diagnostic
acquisition time (100mS Typ)
8/19
Bias (power amp turn-on)
Diagnostic Enable
(Permanent)
FAULT
event
t
Read Data
I2CB DATA
Permanent Diagnostics data (output)
permitted time