TDA7564B

Multiple faults

Doc ID 12734 Rev 4

19/34

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 double-fault possible. 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, in Channels LF and RR, so = CH+, sk = CH-; in Channels LR and RF, 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 micro 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. (*)