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STA530

FUNCTIONAL DESCRIPTION

The circuit contains all the blocks to build a configurable four channel amplifier.

In fact, only driving properly the TRK_2 (and TRK_4) pins, it’s possible to change the chip configuration:

– 50 Watt x 4

– 50 Watt x 2 + 100 Watt x1 (TRK_2/Par1&2 or TRK_4/Par3&4 at -Vs)

– 100 Watt x 2 (TRK_2/Par1&2 and TRK_4/Par3&4 at -Vs)

Each single channel is based on the Output Bridge Power Amplifier, and its protection circuit. Moreover, a sig-

nal rectifier are added to complete the circuit.

The operation modes are driven by The Turn-on/off sequence block. In fact the IC can be set in three states by

the Stby/mute pin:

In the Standby mode all the circuits involved in the signal path are uninhabited, instead

in Mute mode the circuits are biased but the Speakers Outputs are forced to ground potential.

These voltages can be get by the external RC network connected to Stby/Mute pin.

The same block is used to force quickly the I.C. In standby mode or in mute mode when the I.C. dangerous

condition has been detected. The RC network in these cases is used to delay the Normal operation restore.

The protection of the I.C. are implemented by the Over Temperature, Unbalance Ground, Output Short circuit,

Under voltage, and output transistor Power sensing as shown in the following table:

Table 1. Protection Implementation

ABSOLUTE VALUE BLOCK

The absolute value block rectifies the signal to extract the control voltage for the external Buck regulator. The

output voltage swing is internally limited, the gain is internally fixed to 70.

The input impedance of the rectifier is very high , to allow the appropriate filtering of the audio signal before the

rectification.

Fault Type

Condition

Protection strategy

Action time

Release time

Chip Over

temperature

Tj > 130 °C

Mute

Fast

Slow Related to

Turn_on sequence

Chip Over

temperature

Tj > 150 °C

Standby

Fast

Slow, Related to

Turn_on sequence

Unbalancing

Ground

|Vgnd| > ((CD+) -

(CD-))/2 + 5V

Standby

Fast

Slow, Related to

Turn_on sequence

Over Current

Iout > 4.5A

Reducing Buck

regulator output

voltage.

Related to the Buck

regulator

Related to the Buck

regulator

Short circuit

Iout > 5A

Standby

Fast

Slow, related to

Turn_on sequence

Under Voltage

|Vs+| + |Vs-|< 20V

Standby

Fast

Slow, related to

Turn_on sequence

Extra power

dissipation

at output transistor

Pd tr. > 18W

Reducing Buck

regulator output

voltage.

Related to the Buck

regulator

Related to the Buck

regulator

Maximum power

dissipation

at output transistor

Pd tr. > 30W

Standby

Fast

Slow, related to

Turn_on sequence