TDA7801 datasheet(24/48 Pages) STMICROELECTRONICS

24 / 48 page

Functional description

TDA7801

24/48

DocID022674 Rev 4

It is possible to run the turn-on diagnostic several times by simply resetting the D7-IB0

meanwhile the amplifier is in amplifier mode and writing back '1' on D7-IB0 when the

amplifier is in tristate mode.

Between two diagnostic sequences it is necessary to reset the data register by an I2C

reading instruction. Note that the reading instruction has been placed during the second

diagnostic pulse.

The µP can program the TDA7801 in order to run a cycle of turn-on diagnostic and to move

in amplifier-mode at the end of this cycle (Figure 28)); the I2C bus instructions needed to

program this sequence are:

11011000 -00100000-1XXXXXXX-1XXXXXXX

Note:

The diagnostic enable bit (D7-IB0) has to be set before the amplifier mode bit (D7-IB1)

Figure 28. Turn-on diag. cycle with transition in amp. mode. Positive and negative

output behaviour

The information related to the outputs status is read and memorized at the end of the

voltage pulse top. The diagnostic cycle last no more than Td. No audible noise is generated

in the process. As for short to GND / Vs the fault-detection thresholds remain unchanged

independently of the gain setting. They are as in Figure 29.

Table 7. Start-up diagnostic pulse typical timing

Symbol

Parameter

Value

Unit

Min.

Typ.

Max

tSTR(1)

1. These tSTR and tSTF values are relative to capacitors on A3V3 and D3V3 respectively equal to 47 µF and

22 µF. The tSTR and tSTF are proportional to capacitors value.

Start-up diagnostic rise

0.8

1.5

tSH(2)

2. Values relative to fs = 44100Hz.

Short to Vcc/Gnd check

tPL(2)

Plateau time

162

tSTF(1)

Start-up diagnostic fall

8.5

tDELAY(2)

Delay time before play

Diagnostic pulse

182

190

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