11/21

TDA7563PD

the intervention of the short-circuit protection) occurs to the speakers outputs . Once activated, the di-

agnostics procedure develops as follows (fig. 26):

– To avoid momentary re-circulation spikes from giving erroneous diagnostics, a check of the output sta-

tus 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

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 25. Restart timing without Diagnostic Enable (Permanent) - Each 1mS time, a sampling of

the fault is done

Figure 26. Restart timing with Diagnostic Enable (Permanent)

4

OUTPUT DC OFFSET DETECTION

Any DC output offset exceeding ±2 V are signalled out. This inconvenient might occur as a consequence of ini-

tially 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):

t

1-2mS

1mS

1mS

1mS

1mS

Overcurrent and short

circuit protection intervention

(i.e. short circuit to GND)

Short circuit removed

Out

t

Overcurrent and short

circuit protection intervention

(i.e. short circuit to GND)

Short circuit removed

1-2mS

100/200mS

1mS

1mS