TDA7801 datasheet(27/48 Pages) STMICROELECTRONICS

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TDA7801

Functional description

6.6

Multiple faults

Faults can occur simultaneously. If this happens, faults are read out according to a "priority

table" (see Table 8); this guarantees that the most dangerous fault is signalled. This is true

only for the turn-on diagnostic but not in case of permanent diagnostic (only the faults

causing protection intervention are recognized).

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

load, which is not among the recognizable faults. If an open load is present during the

device's normal operation, it should be detected at a subsequent turn-on diagnostic cycle

(i.e. at the successive car radio turn-on).

6.7

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.

The turn-on diagnostic faults are reported on the byte DB 0-3 at the bits D 4-0. The faults

are consistent when the bit D6 of DB0 is '1'. The byte DB 0-3 is reset when read.

During Amplifier-mode, when the bit D4 of byte DB 0-3 is '1' an overload on the

correspondent channel has been detected and a 100 ms permanent diagnostic cycle has

been done. The data on the bits D 4-0 reports the results of this diagnostic cycle. If the bits

are all zero it means that an overload event has been detected, a 100ms cycle has been

performed and the fault has not been detected or removed.

6.8

I2C programming/reading sequence

A correct turn on/off sequence respectful of the diagnostic timings and producing no audible

noises could be as follows (after battery connection):

Turn-on: (Stand-by out + DIag Enable)

 200 ms (min.)  Muting out

Turn-off: Muting in

 10 ms  (Diag disable + stand-by in)

Car radio installation: DIag enable (write)

 200 ms  I2C read (repeat until all

faults disappear).

Table 8. Multiple faults priority

S. GND

S. Vs

S. Across L.

Open L.

S. GND

S. Vs + S. GND

S. GND

S. Vs

S. Across L.

N.A.

Open L.

Open Load (1)

Only in Startup Diagnostic

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