STA530

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OUTPUT BRIDGE

The Output bridge amplifier makes the single-ended to Differential conversion of the Audio signal using two

power amplifiers, one in non-inverting configuration with gain equal to 10 and the other in inverting configuration

with unity gain. To guarantee the high input impedance at the input pins, PWR_Inp1....4, the second amplifier

stages are driven by the output of the first stages respectively.

In 60W x2 channel configuration the "slave" inputs (INPUT 2/4) must be connected to GND.

POWER PROTECTION

To protect the output transistors of the power bridge a power detector is implemented (fig 1).

The current flowing in the power bridge and the voltage drop on the relevant power (Vds) are internally mea-

sured. These two parameters are converted in current and multiplied: the resulting current , Ipd, is proportional

to the instantaneous dissipated power on the relevant output transistor. The current Ipd is compared with the

The aim of the current Iprot is to reduce the reference voltage for the Buck regulator supplying the power stage

of the chip, and than to reduce the dissipated power. The response time of the system must be less than

200

µSec to have an effective protection. As further protection, when Ipd reaches an higher threshold (when the

dissipated value is higher then 30W) the chip is shut down, forcing low the Stby/Mute pin, and the turn on se-

quence is restarted. The above description is relative for each channel in 4x30W configuration.

Figure 1. Power Protection Block Diagram

+

+

x

OPA

OUT1p

ILIMP

I_Pd

I_pda

I_pdp

I_pd

Pdp1

Oc1

I_pd

CURRENT

COMP.

TO PROT

PAD

SEQUENCE

TO TURN-ON/OFF

SEQUENCE

TO TURN-ON/OFF

MULTIPLIER

Iload

CD-1&2

OPA

OUT1n

CD+1&2

V/I

V/I

Ilim

CURRENT

COMP.

D02AU1346