TDA7803A datasheet(31/72 Pages) STMICROELECTRONICS

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DS12195 Rev 7

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TDA7803A

Functional description

loudspeaker with a very high inductance and it took more than 2 ms to get the current

reduced.

A plateau cycle can be recalled by means of a reading procedure of bytes DB1/2/3/4 when

the amplifier is performing the restart cycle. As for the turn-on diagnostic, when DB4 is read

DB1/2/3/4 are reset, therefore the incremental reading is suggested in order not to miss any

data.

Please note that if the over-current cause was removed before the reading the plateau cycle

cannot restart.

6.4

AC diagnostic

The goal of this feature is to detect accidental disconnection of tweeters in 2-way speaker

and, more in general, the presence of capacitive (AC) coupled load. This diagnostic is

based on the notion that the overall speaker's impedance (woofer + parallel tweeter) tends

to increase towards high frequencies if the tweeter gets disconnected. This happens

because the remaining speaker (woofer) would be out of its operating frequency's range

(high impedance).

To determine the load impedance, a sine wave tone of a suitable frequency should be

provided to the output pins and the AC diagnostic is able to determine if the tweeter is

connected or not. The tweeter is not connected if for four consecutive sine waves the

current threshold on the load is not crossed.

AC diagnostic is managed by I2C commands. When IB4 D3 = "1", the AC diagnostic is

enabled; IB4 D4 is used to choose the current level threshold to be used as a reference for

the test.

The results of the AC diagnostic test are stored in DB5 D3..6. It is written "1" if the tweeter

for that channel is present.

The AC diagnostic is able to give the correct results only if the input signal Vout < Vs -4V.

User knows that this condition is verified by reading "0" in DB5 D7. When DB5 D7 = "0", it

mean that the test's signal was too high.

6.5

Input offset detector

Input offset detector aim is to avoid any possible offset that could come from the audio

signal source through I2S/TDM input stream.

For this purpose the TDA7803A input offset detector performs an evaluation of the input

signal and calculates if an offset with values higher that -19.5 dBFS is present.

Moreover, if high pass filter function is selected by means of IB3-d0, the TDA7803A will

eliminate the input offset giving a complete robustness to any disturbance or malfunction

coming from external audio chain blocks.

The input offset detector and high-pass filtering can be used during PLAY mode.

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