TDA7566 Datasheet, PDF (10/19 Pages) STMicroelectronics – MULTIFUNCTION QUAD POWER AMPLIFIER WITH BUILT-IN DIAGNOSTICS FEATURES

TDA7566
b) PERMANENT DIAGNOSTICS.
Detectable conventional faults are:
- SHORT TO GND
- SHORT TO Vs
- SHORT ACROSS THE SPEAKER
The following additional features are provided:
- OUTPUT OFFSET DETECTION
- AC DIAGNOSTIC
The TDA7566 has 2 operating statuses:
1 RESTART mode. The diagnostic is not enabled. Each audio channel operates independently from each
other. If any of the a.m. faults occurs, only the channel(s) interested is shut down. A check of the output
status is made every 1 ms (fig. 17). Restart takes place when the overload is removed.
2 DIAGNOSTIC mode. It is enabled via I2C bus and self activates if an output overload (such to cause
the intervention of the short-circuit protection) occurs to the speakers outputs . Once activated, the di-
agnostics procedure develops as follows (fig. 18):
– To avoid momentary re-circulation spikes from giving erroneous diagnostics, a check of the output
status is made after 1ms: if normal situation (no overloads) is detected, the diagnostic is not per-
formed and the channel returns back active.
– Instead, if an overload is detected during the check after 1 ms, then a diagnostic cycle having a du-
ration of about 100 ms is started.
– After a diagnostic cycle, the audio channel interested by the fault is switched to RESTART mode. The
relevant data are stored inside the device and can be read by the microprocessor. When one cycle
has terminated, the next one is activated by an I2C reading. This is to ensure continuous diagnostics
throughout the car-radio operating time.
– To check the status of the device a sampling system is needed. The timing is chosen at microproces-
sor level (over half a second is recommended).
Figure 17. Restart timing without Diagnostic Enable (Permanent)
Each 1ms time, a sampling of the fault is done
Out
1-2mS
1mS
1mS
1mS
1mS
Overcurrent and short
circuit protection intervention
(i.e. short circuit to GND)
t
Short circuit removed
Figure 18. Restart timing with Diagnostic Enable (Permanent)
1mS
100mS
1mS
1mS
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Overcurrent and short
(i.e. short circuit to GND)
t
Short circuit removed