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TPA3128D2, TPA3129D2

SLOS941C – MAY 2016 – REVISED JANUARY 2018

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Product Folder Links: TPA3128D2 TPA3129D2

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Copyright © 2016–2018, Texas Instruments Incorporated

Typical Application (continued)

8.2.1 Design Requriements

DESIGN PARAMETERS

EXAMPLE VALUE

Input voltage range PVCC

4.5 V to 26 V

PWM output frequencies

300kHz, 400 kHz, 500 kHz, 600 kHz, 1 MHz or 1.2 MHz

Maximum output power

50 W

8.2.2 Detailed Design Procedure

The TPA31xxD2 devices are very flexible and easy to use Class D amplifier; therefore the design process is

straightforward. Before beginning the design, gather the following information regarding the audio system.

•

PVCC rail planned for the design

•

Speaker or load impedance

•

Maximum output power requirement

•

Desired PWM frequency

8.2.2.1 Select the PWM Frequency

Set the PWM frequency by using AM0, AM1 and AM2 pins.

8.2.2.2 Select the Amplifier Gain and Master/Slave Mode

In order to select the amplifier gain setting, the designer must determine the maximum power target and the

speaker impedance. Once these parameters have been determined, calculate the required output voltage swing

which delivers the maximum output power.

Choose the lowest analog gain setting that corresponds to produce an output voltage swing greater than the

required output swing for maximum power. The analog gain and master/slave mode can be set by selecting the

voltage divider resistors (R1 and R2) on the Gain/SLV pin.

8.2.2.3 Select Input Capacitance

Select the bulk capacitors at the PVCC inputs for proper voltage margin and adequate capacitance to support the

power requirements. In practice, with a well-designed power supply, two 100-μF, 50-V capacitors should be

sufficient. One capacitor should be placed near the PVCC inputs at each side of the device. PVCC capacitors

should be a low ESR type because they are being used in a high-speed switching application.

8.2.2.4 Select Decoupling Capacitors

Good quality decoupling capacitors must be added at each of the PVCC inputs to provide good reliability, good

audio performance, and to meet regulatory requirements. X5R or better ratings should be used in this

application. Consider temperature, ripple current, and voltage overshoots when selecting decoupling capacitors.

Also, these decoupling capacitors should be located near the PVCC and GND connections to the device in order

to minimize series inductances.

8.2.2.5 Select Bootstrap Capacitors

Each of the outputs require bootstrap capacitors to provide gate drive for the high-side output FETs. For this

design, use 0.22-μF, 25-V capacitors of X5R quality or better.