TPA3004D2_15 Datasheet, PDF (22/47 Pages) Texas Instruments – 12-W STEREO CLASS-D AUDIO POWER AMPLIFIER WITH DC VOLUME CONTROL

TPA3004D2
SLOS407E – FEBRUARY 2003 – REVISED JANUARY 2011
Class-D Operation
This section focuses on the class-D operation of the TPA3004D2.
www.ti.com
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 37. 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, thus causing a high supply current.
OUTP
OUTN
+12 V
Differential Voltage
Across Load ^{0 V}
–12 V
Current
Figure 37. Traditional Class-D Modulation Scheme's Output Voltage and Current Waveforms Into an
Inductive Load With No Input
TPA3004D2 Modulation Scheme
The TPA3004D2 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 I²R losses in the load.
22
Submit Documentation Feedback
Copyright © 2003–2011, Texas Instruments Incorporated
Product Folder Link(s): TPA3004D2