TDA7803A datasheet(27/72 Pages) STMICROELECTRONICS

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DS12195 Rev 7

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TDA7803A

Functional description

case of IB4 (D1/D2) = 0. The pulse amplitude is stopped when the current flowing

through the speaker Ispeaker is the same as prefixed one Ilow (low current) or because it

reaches the maximum value permitted. When Ispeaker reaches the value Ilow and Vo<

Vopen (open load threshold) then the speaker can be considered as a normal load

(DBx-D2='0'). In all other cases the result will be open load (DBx-D2='1') (see

Figure 32).

Figure 32. Short circuit and open load diagnostic

The whole diagnostic time depends on the number of pulses that are done. At least two

pulses are done, but they could be three in case of open load. The values inserted into the

Table 6, are calculated basing on Fs = 48000 Hz.

In all cases the fault is sent out to the registers only if it is stable throughout the whole

plateau period. If this condition is not respected, any possible misconnections (Soft-short,

Short to VCC/GND, Short Across or Open Load) won't be reported. The faults for the turn-

on diagnostic are written in DB (1, 2, 3, 4) (D1, D2, D3, D4) (a byte for each channel and a

bit for each fault). They are consistent if DB0 D6 = "1". After a reading the data byte are

reset.

The fault-detection thresholds for short to GND/ Vs remain unchanged independently from

the gain setting. They are as in Figure 33.

Figure 33. Short to GND and short to Vs, threshold description

Concerning the short across the speaker / open speaker, the threshold changes from line

driver mode and speaker mode diagnostic setting, as load expected are pretty different

(either normal speaker's impedance or high impedance). Speaker or line driver mode is

selectable from IB4 D2 for channels 1 and 3 and IB4 D1 for channel 2 and 4. The values in

case of speaker mode are as in Figure 34. The same thresholds will change as in Figure 35,

if line driver mode diagnostic is selected.

Figure 34. Short across the speaker and open load threshold description, in speaker

mode

GAPGPS00806

TSTR

TSTF

TPL

TRD

½*VS

Short to

GND

Short to

Normal Operation

Vs -2V

Vs -1V

GAPGPS00807

GAPGPS00808

Open Load

Normal Load

Short Across

Load

0.5

Ω 1.5Ω

infinite

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