TDA8929T Datasheet, PDF (7/36 Pages) NXP Semiconductors – Controller class-D audio amplifier

Philips Semiconductors
Controller class-D audio amplifier
Preliminary specification
TDA8929T
8 FUNCTIONAL DESCRIPTION
The combination of the TDA8926J and the TDA8929T
produces a two-channel audio power amplifier system
using the class-D technology (see Fig.4).
In the TDA8929T controller device the analog audio input
signal is converted into a digital Pulse Width Modulation
(PWM) signal. The digital power stage (TDA8926) is used
for driving the low-pass filter and the loudspeaker load. It
performs a level shift from the low-power digital
PWM signal, at logic levels, to a high-power PWM signal
that switches between the main supply lines.
A second-order low-pass filter converts the PWM signal
into an analog audio signal across the loudspeaker.
For a description of the power stage see the specification
of the TDA8926.
The TDA8926 can be used for an output power of
2 × 50 W. The TDA8927 should be used for a higher
output power of 2 × 100 W.
8.1 Controller
The controller contains (for two audio channels) two Pulse
Width Modulators (PWMs), two analog feedback loops
and two differential input stages. This chip also contains
circuits common to both channels such as the oscillator, all
reference sources, the mode functionality and a digital
timing manager.
The pinning of the TDA8929T and the power stage devices
are designed to have very short and straight connections
between the packages. For optimum performance the
interconnections between the packages must be as short
as possible.
Using this two-chip set an audio system with two
independent amplifier channels with high output power,
high efficiency (90%) for the system, low distortion and a
low quiescent current is obtained. The amplifiers channels
can be connected in the following configurations:
• Mono Bridge-Tied Load (BTL) amplifier
• Stereo Single-Ended (SE) amplifier.
The amplifier system can be switched in three operating
modes via the mode select pin:
• Standby: with a very low supply current
• Mute: the amplifiers are operational, but the audio signal
at the output is suppressed
• On: amplifier fully operational with output signal.
For suppressing pop noise the amplifier will remain
automatically for approximately 220 ms in the mute mode
before switching to operating mode. In this time the
coupling capacitors at the input are fully charged.
Figure 3 shows an example of a switching circuit for driving
pin MODE.
handbook, halfpage
+5 V
standby/
mute
mute / on
R
MODE
R
SGND
MGW150
Fig.3 Mode select switch circuitry.
2001 Dec 11
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