TDA7572 datasheet(39/64 Pages) STMICROELECTRONICS

39 / 64 page

TDA7572

Input stage and gain compressor

39/64

ATTACK[1:0]: Sets the maximum Attack rate of the gain compressor according to the table

below:

Setting in NOI2CBUS mode:

I2CDATA/AttackSel - pin 51 -> Attack/release rate selection

ADDR1/CompEnable - pin 54 -> Gain compression effort selection

6.2.2

Soft-mute function, without pre-limiter

Well-behaved over-modulation protection and current-limiting allow this IC to not require a

pre-limiter before the modulator. This allows the amplifier to always take advantage of the

available supply voltage. A limited output voltage can be done in a crude manner by using

AOUT's max output swing, and counting on its clipping signal to drive the compressor.

A soft mute/unmute is incorporated at AOUT. It works by slowly muxing AOUT from the input

signal to SVR. In this way, dc offsets occurring in any upstream stages are kept inaudible.

The mux slew time is determined by the voltage slew rate at the MUTE_L pin (pin 10), which

is asserted low. Mute can by driven either be by external means, or controlled by I2C

command.

The MUTE bit, present in the input control register (D0, InputControl register), controls

muting by discharging or charging the MUTE_L pin. The default value for this bit for NOI2C

mode is 0 that lead to a charging of mute cap. Abrupt muting is available by use of the

MuteSpeed bit. When MuteSpeed is asserted, MUTE_L is rapidly charged and discharged

by a small resistance (approximately 500 ohms). In the pictures below are reported the two

application circuits and the internal circuitry of mute correspondent to.

Figure 3.

Mute by external command

Table 30.

Sets the maximum attack rate of the gain compressor

Attack [1:0]

Clock counts

Nominal time at 400KHz clock

160µs

320µs

640µs

1.28ms

Table 31.

Attack/release rate and gain compression effort selection

INPUT PIN/VALUE

DGND

VDIG

Pin 51

Attack[1:0] = “10”

Release[1:0] = “10”

Attack[1:0] = “11”

Release[1:0] = “11”

Pin 54

GainTable[1:0]=”00”

GainTable[1:0]=”01”

External

Mute

Mute_L

100µA

AC00015

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