When the

µP reads correctly all the 3 bytes containing the mentioned information and gives the last ac-

knowledge, the TDA7476 switches to the ”permanent diagnostic operation”

B) PERMANENT DIAGNOSTIC

It can sense the following diagnostic information:

CH1, CH2, CH3, CH4, CH5

- Short Circuit to GND

- Short Circuit to Vs

Aux1, Aux2

- Short Circuit to GND (*)

- Open Load (*)

(*) Detected if the high side drivers attached to the Aux outputs are ON.

In this case the above conditions are not detected while the single infrasonic current pulse is present

but before. The fault condition must be present for more than 2sec. (typ) and must be also true dur-

ing the pulse, where the data are memorized and then transmitted.

The bytes from/to

µP and TDA7476 are the same as those in case of turn-on diagnostic (see above).

Here following is the permanent diagnostic output Data Bytes. The bits D7 and D6 of the first byte both

stand at 0 level. This condition, although not possible during the turn-on diagnostic, can be useful to con-

firm that the bytes are referred to the permanent diagnostic.

READ BYTE 1

MSB

LSB

STATUS

D7

D6

D5

D4

D3

D2

D1

D0

X

XXX1

1

X

0

CH1 short circuit to Vs

X

XXX1

1

0

X

CH1 short circuit to GND

X

XXX1

0

1

1

CH1 open load

X

XXX0

1

1

1

CH1 short circuit across the load

1

1

X

0

X

X

X

X

CH2 short circuit to Vs

1

1

0

X

X

X

X

X

CH2 short circuit to GND

1

0

1

1

X

X

X

X

CH2 open load

0

1

1

1

X

X

X

X

CH2 short circuit across the load

READ BYTE 2

X

XXX1

1

X

0

CH3 short circuit to Vs

X

XXX1

1

0

X

CH3 short circuit to GND

X

XXX1

0

1

1

CH3 open load

X

XXX0

1

1

1

CH3 short circuit across the load

1

1

X

0

X

X

X

X

CH4 short circuit to Vs

1

1

0

X

X

X

X

X

CH4 short circuit to GND

1

0

1

1

X

X

X

X

CH4 open load

0

1

1

1

X

X

X

X

CH4 short circuit across the load

READ BYTE 3

X

X

X

X

X

X

1

0

AUX1 short circuit to GND

X

X

X

X

X

X

0

1

AUX1 open load

X

XXX1

0

X

X

AUX2 short circuit to GND

X

XXX0

1

X

X

AUX2 open load

1

1

X

0

X

X

X

X

CH5 short circuit to Vs

1

1

0

X

X

X

X

X

CH5 short circuit to GND

1

0

1

1

X

X

X

X

CH5 open load

0

1

1

1

X

X

X

X

CH5 short circuit across the load

TDA7476

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