TDA7575

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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 I

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 than half a second is recommended).

Fig. G: Restart timing without Diagnostic Enable (Permanent)

Each 1mS time, a sampling of the fault is done

Fig H: Restart timing with Diagnostic Enable (Permanent)

OUTPUT DC OFFSET DETECTION.

Any DC output offset exceeding +/- 2 V 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.

circuit protection intervention

t

1-2mS

1mS

1mS

1mS

1mS

Overcurrent and short

(i.e. short circuit to GND)

Short circuit removed

Out

circuit protection intervention

t

Overcurrent and short

(i.e. short circuit to GND)

Short circuit removed

1mS

100mS

1mS

1mS