STA575

2/20

DESCRIPTION (continued)

Notice that normally only one Digital Converter is needed to supply a stereo or multi-channel amplifier system,

therefore most of the functions implemented in the circuit have summing outputs

The signal circuits are biased by fixed negative and positive voltages referred to Ground. Instead the final stag-

es of the output amplifiers are supplied by two external voltages that are following the audio signal . In this way

the headroom for the output transistors is kept at minimum level to obtain a high efficiency power amplifier.

The Compressor circuits, one for each channel, performs a particular transfer behavior to avoid the dynamic

restriction that an adaptive system like this requires. To have a high flexibility the attack / release time and the

threshold levels are externally programmable. The tracking signal for the external digital converter is generated

from the Absolute Value block that rectifies the audio signal present at the compressor output. The outputs of

these blocks are decoupled by a diode to permit an easy sum of this signal for the multichannel application. The

output power bridges have a dedicated input pin to perform an AC decoupling to cancel the compressor output

DC offset. The gain of the stage is equal to 4 (+12dB). A sophisticated circuit performs the output transistor pow-

er detector that , with the digital converter, reduces the power supply voltage . Moreover, a maximum current

output limiting and the over temperature sensor have been added to protect the circuit itself. The external volt-

age applied to the STBY/MUTE pin forces the two amplifiers in the proper condition to guarantee a silent turn-

on and turn-off.

ABSOLUTE MAXIMUM RATINGS

Note 2: All pins withstand

±2KV ESD but not pin 11

Symbol

Parameter

Value

Unit

Positive supply voltage referred to pin 13 (GND)

30

V

Negative supply voltage referred to pin 13 (GND)

-24

V

Positive supply voltage tracking rail referred to pin 13 (GND)

22

V

0.3

V

-0.3

V

Negative supply voltage tracking rail referred to pin 13 (GND)

-22

V

Pin 3, 25 Negative & Positive maximum voltage referred to GND

(pin 13)

-0.5 to +20

V

Pin 7, 21, 18, 10 Negative & Positive maximum voltage referred to

GND (pin 13)

-20 to +20

V

Pin 8, 20 Negative & Positive maximum voltage referred to GND

(pin 13)

-0.5 to +0.5

V

Pin 17 Negative & Positive maximum voltage referred to GND (pin

13)

-7 to +0.5

V

Pin 11 maximum input current (Internal voltage clamp at 5V)

500

µA

Pin 11 negative maximum voltage referred to GND (pin 13)

-0.5

V

Output current

7.7

A