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Figure 5. Hardware mute application schematic

Figure 5. Hardware mute application schematic

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FDA2100LV



6



Diagnostics functional description



Diagnostics functional description

The FDA amplifiers family provides diagnostic functions to detect several possible fault

conditions. Any warning information will be stored in the I2C interface and kept until the first

I2C bus reading operation. Here reported the FDA2100LV's diagnostic features:



6.1







Load detection







Under/over voltage events







Chip over temperature







Digital input offset







Output clipping







Over temperature of an external component (i.e. step-up DMOS) through a suitable

NTC external sensor







Output current digital acquisition



Load detection

A new concept of load diagnostic is provided by the FDA family, specially designed for

automotive applications. Advanced digital algorithms make tests extremely reliable.

The FDA family load diagnostic is performed in three phases and can be classified in:





Turn on diagnostic







AC/DC diagnostic







Permanent diagnostic



While turn on and permanent tests are automatically made by FDA, AC/DC can be

enabled/disabled by means of I2C bus.

During AC/DC load test the I2C acknowledge is kept low.

AC/DC load test signal is generated and test is done, independently of software mute value

(IB6 D0-D1), only if:

1.



operation mode passes from st-by to I2C mode through enable pin setting;



2.



DC test enable is 1 (IB2 D7);



3.



the desired channel is put in working mode (IB1 D7-D6);



4.



FDA is NOT kept in hardware mute (by means of the dedicated pin).



This means that if the first I2C programming sets PWM off in a channel, the test is not made

on that channel (relative test result must be discharged). To perform a test on that channel,

or simply to repeat the load detection test, the amplifier must be switched off by enable pins

(operation mode set to 000), and the I2C setting re-sent.

Out of phase modulation option, if desired, must be selected after the AC-DC load

diagnostic execution to avoid pop noise.



Rev 1



25/61

60



Diagnostics functional description



FDA2100LV

Figure 6. Load diagnostic diagram



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Note:



Audio data coming from I2S are ignored until time T6. Un-muting starts after T6.

If DC diagnostic is not selected, un-muting starts after T2.

Startup and diagnostic timing can be squeezed by a factor around /50 starting-up the device

with dedicated I2C setup: Fast startup mode IB7 [D4-D0] = 00110. In this case diagnostic is

working, but less reliable and pop-generating. After fast startup, it is strongly suggested to

come back to normal operating mode (IB7 [D4-D0] = 00000) to avoid fast timing in case of

over current events.



6.1.1



Turn-on diagnostic

The turn-on diagnostic performs:





shorts and "soft shorts" to Vdd







shorts and "soft shorts" to GND







mixed shorts "soft shorts" Vdd/GND (i.e. OUT1+ to Vdd & OUT1- to GND)



In the following picture some examples of possible "soft shorts" conditions.

The output power MOSFETS of the channel having a short to Vdd or GND detected are kept

into three-state condition (for more details refer to Section 6.3).

In case of DC load diagnostic occurring after a short to Vcc or GND detected, the device

stays muted on both channels, and I2C is no longer accessible.

An enable reset is needed to exit from this state.



26/61



Rev 1



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Figure 5. Hardware mute application schematic

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