TDA7566

Diagnostics functional description

Doc ID 9801 Rev 6

15/29

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 1 ms time, a sampling of the fault is done

Figure 23.

Restart timing with diagnostic enable (Permanent)

4.3

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.

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

(i.e. short circuit to GND)

Short circuit removed

1mS

100mS

1mS

1mS