TDA7562B

Diagnostics functional description

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Figure 20.

Thresholds for short across the speaker/open speaker

same thresholds will change as follows:

Figure 21.

Thresholds for line-drivers

4.2

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

–

AC diagnostic

The TDA7562B has 2 operating statuses:

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 shutdown. A check of the output status is made every 1 ms (Figure 22).

Restart takes place when the overload is removed.

2.

to cause the intervention of the short-circuit protection) occurs to the speakers outputs.

Once activated, the diagnostics procedure develops as follows (Figure 23):

–

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 by

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).