Datasheet

0V
-12V
+12V
Current
OUTP
OUTN
Differential
Voltage
Across
Load
0V
-12V
+12V
Current
OUTP
OUTN
Differential
Voltage
Across
Load
Output=0V
Output>0V
TPA3112D1
www.ti.com SLOS654C –SEPTEMBER 2009–REVISED JULY 2012
CLASS-D OPERATION
This section focuses on the class-D operation of the TPA3112D1.
TPA3112D1 Modulation Scheme
The TPA3112D1 uses a modulation scheme that allows operation without the classic LC reconstruction filter
when the amp is driving an inductive load. Each output is switching from 0 volts to the supply voltage. The OUTP
and OUTN are in phase with each other with no input so that there is little or no current in the speaker. The duty
cycle of OUTP is greater than 50% and OUTN is less than 50% for positive output voltages. The duty cycle of
OUTP is less than 50% and OUTN is greater than 50% for negative output voltages. The voltage across the load
sits at 0 V throughout most of the switching period, greatly reducing the switching current, which reduces any I
2
R
losses in the load.
Figure 18. The TPA3112D1 Output Voltage and Current Waveforms Into an Inductive Load
Ferrite Bead Filter Considerations
Using the Advanced Emissions Suppression Technology in the TPA3112D1 amplifier it is possible to design a
high efficiency Class-D audio amplifier while minimizing interference to surrounding circuits. it is also possible to
accomplish this with only a low-cost ferrite bead filter. In this case it is necessary to carefully select the ferrite
bead used in the filter.
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Product Folder Link(s): TPA3112D1