TDA7566_06 Datasheet, PDF (15/28 Pages) STMicroelectronics – 4x40W multifunction quad power amplifier with built-in diagnostics features

TDA7566
Diagnostics functional description
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 22. Restart timing without Diagnostic Enable (Permanent)
Each 1ms time, a sampling of the fault is done
1-2mS
1mS
1mS
1mS
1mS
Out
Overcurrent and short
circuit protection intervention
(i.e. short circuit to GND)
t
Short circuit removed
Figure 23. Restart timing with Diagnostic Enable (Permanent)
1mS
100mS
1mS
1mS
Overcurrent and short
(i.e. short circuit to GND)
t
Short circuit removed
4.3
Output DC offset detection
Any DC output offset exceeding ±2V are signalled out. This inconvenient might occur as a
consequence of initially defective or aged and worn-out input capacitors feeding a DC
component to the inputs, so putting the speakers at risk of overheating.
This diagnostic has to be performed with low-level output AC signal (or Vin = 0).
The test is run with selectable time duration by microprocessor (from a "start" to a "stop"
command):
START = Last reading operation or setting IB1 - D5 - (OFFSET enable) to 1
STOP = Actual reading operation
Excess offset is signalled out if persistent throughout the assigned testing time. This feature
is disabled if any overloads leading to activation of the short-circuit protection occurs in the
process.
4.4
AC diagnostic
It is targeted at detecting accidental disconnection of tweeters in 2-way speaker and, more
in general, presence of capacitively (AC) coupled loads.
This diagnostic is based on the notion that the overall speaker's impedance (woofer +
parallel tweeter) will tend to increase towards high frequencies if the tweeter gets
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