Datasheet

0V
-12V
+12V
Current
OUTP
DifferentialVoltage
AcrossLoad
OUTN
TPA3106D1
www.ti.com SLOS516C –OCTOBER 2007–REVISED AUGUST 2010
CLASS-D OPERATION
This section focuses on the class-D operation of the TPA3106D1.
Traditional Class-D Modulation Scheme
The traditional class-D modulation scheme, which is used in the TPA032D0x family, has a differential output
where each output is 180 degrees out-of-phase and changes from ground to the supply voltage, V
CC
. Therefore,
the differential prefiltered output varies between positive and negative V
CC
, where filtered 50% duty cycle yields 0
V across the load. The traditional class-D modulation scheme with voltage and current waveforms is shown in
Figure 26. Note that even at an average of 0 V across the load (50% duty cycle), the current to the load is high,
causing high loss and thus causing a high supply current.
Figure 26. Traditional Class-D Modulation Scheme's Output Voltage and Current Waveforms into an
Inductive Load With No Input
TPA3106D1 Modulation Scheme
The TPA3106D1 uses a modulation scheme that still has each output switching from 0 to the supply voltage.
However, OUTP and OUTN are now in phase with each other with no input. 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.
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Product Folder Link(s): TPA3106D1