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TPA3221

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SLASEE9 – JUNE 2017

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Copyright © 2017, Texas Instruments Incorporated

Typical Applications (continued)

10.2.1.1 Design Requirements

For this design example, use the parameters in Table 7.

Table 7. Design Requirements, BTL Application

DESIGN PARAMETER

EXAMPLE

ExternalLow Power Supply

5 V

High Power Supply

7 - 30 V

Analog Inputs

IN1_M = ±3.9V (peak, max)

IN1_P = ±3.9V (peak, max)

IN2_M = ±3.9V (peak, max)

IN2_P = ±3.9V (peak, max)

Output Filters

Inductor-Capacitor Low Pass FIlter (10 µH + 1 µF)

Speaker Impedance

3 - 8 Ω

10.2.1.2 Detailed Design Procedures

A rising-edge transition on RESET input allows the device to execute the startup sequence and starts switching.

A toggling OTW_CLIP signal is indicating that the output is approaching clipping. The signal can be used either

to decrease audio volume or to control an intelligent power supply nominally operating at a low rail adjusting to a

higher supply rail.

The device is inverting the audio signal from input to output.

The AVDD pin is not recommended to be used as a voltage source for external circuitry when internal LDO is

enabled (VDD

≥ 7 V).

10.2.1.2.1

Decoupling Capacitor Recommendations

In order to design an amplifier that has robust performance, passes regulatory requirements, and exhibits good

audio performance, good quality decoupling capacitors should be used. In practice, X7R should be used in this

application.

The voltage of the decoupling capacitors should be selected in accordance with good design practices.

Temperature, ripple current, and voltage overshoot must be considered. This fact is particularly true in the

selection of the 1μF that is placed on the power supply to each full-bridge. It must withstand the voltage

overshoot of the PWM switching, the heat generated by the amplifier during high power output, and the ripple

current created by high power output. A minimum voltage rating of 50 V is required for use with a 30 V power

supply.

10.2.1.2.2

PVDD Capacitor Recommendation

The large capacitors used in conjunction with each full-bridge, are referred to as the PVDD Capacitors. These

capacitors should be selected for proper voltage margin and adequate capacitance to support the power

requirements. In practice, with a well designed system power supply, 470 μF, 50 V supports most applications.

The PVDD capacitors should be low ESR type because they are used in a circuit associated with high-speed

switching.

10.2.1.2.3

BST capacitors

To ensure large enough bootstrap energy storage for the high side gate drive to work correct with all audio

source signals, 33 nF / 50V X7R BST capacitors are recomemnded.

10.2.1.2.4

PCB Material Recommendation

FR-4 Glass Epoxy material with 2 oz. (70 μm) copper is recommended for use with the TPA3221. The use of this

material can provide for higher power output, improved thermal performance, and better EMI margin (due to

lower PCB trace inductance.