TDA8924TH datasheet(6/35 Pages) PHILIPS

6 / 35 page

2003 Jul 28

Philips Semiconductors

Objective speciﬁcation

× 120 W class-D power ampliﬁer

TDA8924

FUNCTIONAL DESCRIPTION

8.1

General

The TDA8924 is a two channel audio power amplifier using

class-D technology. A typical application diagram is

illustrated in Fig.38. A detailed application reference

design is given in Section 16.8.

The audio input signal is converted into a digital Pulse

Width Modulated (PWM) signal via an analog input stage

and PWM modulator. To enable the output power

transistors to be driven, this digital PWM signal is applied

to a control and handshake block and driver circuits for

both the high side and low side. In this way a level shift is

performed from the low power digital PWM signal (at logic

levels) to a high power PWM signal which switches

between the main supply lines.

A 2nd-order low-pass filter converts the PWM signal to an

analog audio signal across the loudspeaker.

The TDA8924 one-chip class-D amplifier contains high

power D-MOS switches, drivers, timing and handshaking

between the power switches and some control logic. For

protection a temperature sensor and a maximum current

detector are built-in.

Each of the two audio channels of the TDA8924 contains

a PWM, an analog feedback loop and a differential input

stage. The TDA8924 also contains circuits common to

both channels such as the oscillator, all reference sources,

the mode functionality and a digital timing manager.

The TDA8924 contains two independent amplifier

channels with high output power, high efficiency (90 %),

low distortion and a low quiescent current. The amplifier

channels can be connected in the following configurations:

• Mono Bridge-Tied Load (BTL) amplifier

• Stereo Single-Ended (SE) amplifiers.

The amplifier system can be switched in three operating

modes with pin MODE:

• Standby mode; with a very low supply current

• Mute mode; the amplifiers are operational, but the audio

signal at the output is suppressed

• Operating mode; the amplifiers are fully operational with

output signal.

An example of a switching circuit for driving pin MODE is

illustrated in Fig.3.

For suppressing plop noise the amplifier will remain

automatically in the mute mode for approximately 150 ms

before switching to the operating mode (see Fig.4).

During this time, the coupling capacitors at the input are

fully charged.

handbook, halfpage

standby/

mute

mute/on

MODE pin

SGND

MBL463

+5 V

Fig.3 Example of mode select circuit.

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