FDA903D-EHT datasheet(26/82 Pages) STMICROELECTRONICS

26 / 82 page

Finite state machine

FDA903D

26/82

DocID031502 Rev 2

7.2

Standby state

ENABLE1, ENABLE2, ENABLE3, ENABLE4 pins have a double function: set of I2C

addresses and start-up of the system.

If ENABLE1/2/3/4 are all low, ("000"), then the FDA903D is off, the outputs remain biased to

ground and the current consumption is limited to Isb. In this case the FSM is in "Standby"

state.

7.3

Diagnostic Vcc-Gnd state

After exiting from Stand-By state the device passes through Diagnostic Vcc/Gnd state.

In this state the amplifier checks the presence of the following faults:



Shorts to ground or to Vcc;



Under-voltage (UVLOVCC);



Thermal shutdown

FDA903D will then move to the next state (Eco-mode) only if there isn't any of these faults

for at least 90ms, thus avoiding any danger for the amplifier and the user system.

Meanwhile, if a stable fault is present, it will be communicated to the user via I2C after

90 ms, in order to provide always only stable information about the system. In this case the

device will not move to Eco-mode, waiting for the fault cause removal

While the amplifier is in Diagnostic Vcc-Gnd state it can receive all the I2C commands, but it

will turn-on the PWM only when it enters in the next state: ECO-mode. This procedure

prevents wrong or unwanted I2C communication to bring the amplifier into dangerous

situation (if a short to Vcc or Gnd is present).

Following conditions will move the amplifier in Diagnostic Vcc-Gnd state from any other

functional state:



Over current protection trigger



UVLOVCC



Over voltage (through DUMP condition)



Thermal shutdown

7.4

ECO-mode state

In ECO-mode state the amplifier is fully operative from a communication point of view and

can receive and actuate all the commands given by the user.

In ECO-mode the output switching is disabled, thus allowing low quiescent current

consumption and therefore low power dissipation. The device is also able to move from

ECO-mode state to MUTE state, turning on the output switching, within about 1 ms -

without experiencing POP-noise.

This allows a very fast transition from ECO-mode to PLAY.

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