TDA8924 Datasheet, PDF (6/35 Pages) NXP Semiconductors – 2 x 120 W class-D power amplifier

Philips Semiconductors
2 × 120 W class-D power amplifier
Objective specification
TDA8924
8 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.
+5 V
handbook, halfpage
standby/
mute
R
R
mute/on
MODE pin
SGND
MBL463
Fig.3 Example of mode select circuit.
2003 Jul 28
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