Diagnostics functional description

TDA7567PD

14/30

Doc ID 16903 Rev 1

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.

(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

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

Figure 12. Restart timing with diagnostic enable (permanent)

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