TDA7567PD Datasheet, PDF (14/30 Pages) STMicroelectronics – 4 x 50 W differential quad power amplifier with built-in diagnostics features

Diagnostics functional description
TDA7567PD
3.2
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
The TDA7567PD has 2 operating status:
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 (Figure 11).
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 diagnostics procedure develops as follows (Figure 12):
– 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 performed and the channel returns back active.
– Instead, if an overload is detected during the check after 1 ms, then a diagnostic
cycle having a duration 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 microprocessor level (over half a second is recommended).
Figure 11. 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 12. Restart timing with diagnostic enable (permanent)
1-2mS
100/200mS
1mS
1mS
14/30
Overcurrent and short
circuit protection intervention
(i.e. short circuit to GND)
Doc ID 16903 Rev 1
t
Short circuit removed