TPA3221 is designed as a feature-enhanced cost efficient high power Class-D audio amplifier. The device has built-in advanced protection circuitry to provide maximum product robustness as well as a flexible feature set including built in LDO for easy supply of low voltage circuitry, selectable gain, switching frequency, controller/peripheral synchronization of multiple devices, selectable PWM modulation scheme, mute function, temperature and clipping status signals. TPA3221 has a bandwidth up to 100kHz and low output noise designed for high resolution audio applications and accepts both differential and single ended analog audio inputs at levels from 1V_RMS to 2V_RMS. With the closed loop operation TPA3221 is designed for high audio performance with a system power supply between 7V and 30V.

To facilitate system design, the TPA3221 needs only a (typical) 30V power stage supply. The TPA3221 has an internal voltage regulator supplied from the VDD pin for the analog and digital system blocks and the output stage gate drive respectively. The VDD pin can be connected directly to PVDD in case of only this power supply rail being available.

To reduce device power losses an external 5V supply can be used for the AVDD and VDD supply pins. The internal voltage regulator connected to the VDD pin is automatically turned off if an external 5V supply is used for this pin. Although supplied from the same 5V source, separating AVDD and VDD on the printed-circuit board (PCB) by RC filters (see application diagram for details) is recommended. These RC filters provide the recommended high-frequency isolation. Special attention should be paid to placing all decoupling capacitors as close to their associated pins as possible. In general, the physical loop with the power supply pins, decoupling capacitors and GND return path to the device pins must be kept as short as possible and with as little area as possible to minimize induction (see Section 9.4.2 for additional information).

The floating supplies for the output stage high side gate drives are supplied by built-in bootstrap circuitry requiring only an external capacitor for each half-bridge.

For a properly functioning bootstrap circuit, a small ceramic capacitor must be connected from each bootstrap pin (BST_X) to the power-stage output pin (OUT_X). When the power-stage output is low, the bootstrap capacitor is charged through an internal diode connected between the gate-drive power-supply pin (GVDD) and the bootstrap pins. When the power-stage output is high, the bootstrap capacitor potential is shifted above the output potential and thus provides a voltage supply for the high-side gate driver. TI recommends to use 33nF ceramic capacitors, size 0603 or 0805, for the bootstrap supply. These 33nF capacitors maintain sufficient energy storage, even during minimal PWM duty cycles, to keep the high-side power stage FET (LDMOS) fully turned on during the remaining part of the PWM cycle.

Special attention is paid to the power stage power supply; this includes component selection, PCB placement, and routing.

For peak electrical performance, EMI compliance, and system reliability, maintaining that each PVDD_X node is decoupled with 1μF ceramic capacitors placed as close as possible to the PVDD supply pins is important . TI recommends to follow the PCB layout of the TPA3221 reference design. For additional information on recommended power supply and required components, see the application diagrams in this data sheet.

If using external power supply for the AVDD and VDD internal regulators, this supply is from a low-noise, low-output-impedance voltage regulator. Likewise, the 30V power stage supply is assumed to have low output impedance throughout the entire audio band, and low noise. The power supply sequence is not critical as facilitated by the internal power-on-reset circuit, but TI recommends to release RESET after the power supply is settled for minimum turn on audible artifacts. Moreover, the TPA3221 is fully protected against erroneous power-stage turn on due to parasitic gate charging. Thus, voltage-supply ramp rates (dV/dt) are noncritical within the specified range (see the Electrical Characteristics table of this data sheet).