TDA7803A-QLX datasheet(29/72 Pages) STMICROELECTRONICS

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DS12195 Rev 7

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TDA7803A

Functional description

When the amplifier is biased and the IB4 D0 = "1", the permanent diagnostic is enabled. The

turn-on diagnostic state is held until an over current event is triggered. When this happens,

a new diagnostic cycle can start.

6.3

Permanent diagnostic

The detectable faults are (see Table 5 for definitions):



Short to GND



Short to Vs



Short across the speaker

Then the following additional features are also provided:



Input offset detection



AC diagnostic

When an over current event occurs, TDA7803A has two different cycles that could react

with:



Restart cycle: it is a 2 ms pulse. During this period a check of the output is performed.



Plateau cycle: it is an 80 ms cycle. During this period a check of the outputs is

performed and the results of diagnostic analysis are written into the I2C bus.

TDA7803A has two different operating behaviors when an over current event is detected:



Restart mode, (IB4 D0 = "0"). The diagnostic is not enabled. Each audio channel

operates independently from each other. If any of the above mentioned faults occurs,

only the channel(s) where the fault happened is shut down. The diagnostic performs

restart cycles every 2 ms until the fault condition is present. The amplifier restarts in

play only once the overload is removed. In Restart mode reporting diagnostic results

are turned off and the corresponding bits in the channels’ data byte registers will be

reset accordingly.



Diagnostic mode, (IB4 D0 = "1"). It is enabled via I2C and self activated if an output

overload occurs to the speaker outputs. If any of the above mentioned faults occurs,

Ihigh

Test current for the short

load pulse

200

-mA

For speaker mode

For line driver mode

Ilow

Test current for the open

load pulse

For speaker mode

For line driver mode

1. For typical loudspeaker of 2 and 4 ohm.

2. These numbers are evaluated in simulation.

3. Typical values for 4 Ω and 2 Ω and zero offset. These numbers depend on the loudspeaker and also on the

intrinsic offset of the amplifier. For 2 Ω loudspeaker, -30 mV offset and Fs = 48 kHz TRU = 21.2 ms; for 4 Ω

and same surrounding conditions TRU = 22.1 ms. Under these conditions TPL = 122.4 ms for 2 Ω and 124.4

for 4 Ω. For higher values the number are not reported here.

Table 6. Start-up pulse typical timings (Fs = 48 kHz) (continued)

Symbol

Parameter

Min

Typ

Max

Unit

Note

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