Multiple faults

TDA7561

16/27

Doc ID 8326 Rev 6

5

Multiple faults

When more misconnections are simultaneously in place at the audio outputs, it is

guaranteed that at least one of them is initially read out. The others are notified after

successive cycles of I2C reading and faults removal, provided that the diagnostic is enabled.

This is true for both kinds of diagnostic (turn on and permanent).

The table below shows all the couples of possible double-fault. It should be taken into

account that a short circuit with the 4 ohm speaker unconnected is considered as double

fault.

S. GND (so) / S. GND (sk) in the above table make a distinction according to which of the 2

outputs is shorted to ground (test-current source side= so, test-current sink side = sk). More

precisely, so = CH+, sk = CH-.

In permanent diagnostic the table is the same, with only a difference concerning Open

Load(*), which is not among the recognizable faults. Should an Open Load be present during

the device's normal working, it would be detected at a subsequent Turn on Diagnostic cycle

(i.e. at the successive Car Radio Turn on).

5.1

Faults availability

All the results coming from I2C bus, by read operations, are the consequence of

measurements inside a defined period of time. If the fault is stable throughout the whole

period, it will be sent out.

To guarantee always resident functions, every kind of diagnostic cycles (Turn-on,

Permanent, Offset) will be reactivate after any I2C reading operation. So, when the

microprocessor reads the I2C, a new cycle will be able to start, but the read data will come

from the previous diag. cycle (i.e. The device is in turn-on state, with a short to GND, then

the short is removed and micro reads I2C. The short to GND is still present in bytes,

because it is the result of the previous cycle. If another I2C reading operation occurs, the

bytes do not show the short). In general to observe a change in diagnostic bytes, two I2C

reading operations are necessary.

Table 5.

Double fault table for turn-on diagnostic

S. GND (so)

S. GND (sk)

S. Vs

S. Across L.

Open L.

S. GND (so)

S. GND

S. GND

S. Vs + S.

GND

S. GND

S. GND

S. GND (sk)

/

S. GND

S. Vs

S. GND

Open L. (*)

S. Vs

/

/

S. Vs

S. Vs

S. Vs

S. Across L.

/

/

/

S. Across L.

N.A.

Open L.

/

/

/

/

Open L. (*)