11.1 Layout Guidelines

The TPA3126D2 can be used with a small, inexpensive ferrite bead output filter in most applications. However, because the Class-D switching edges are fast, the layout of the printed circuit board must be planned carefully. The following suggestions helps to meet EMC requirements.

• Decoupling capacitors — The high-frequency decoupling capacitors should be placed as close to the PVCC and AVCC terminals as possible. Large (100-μF or greater) bulk power supply decoupling capacitors should be placed near the TPA3126D2 on the PVCC supplies. Local, high-frequency bypass capacitors should be placed as close to the PVCC pins as possible. These caps can be connected to the IC GND pad directly for an excellent ground connection. Consider adding a small, good quality low ESR ceramic capacitor between 220-pF and 1-nF, and a larger mid-frequency cap of value between 100-nF and 1-µF also of good quality to the PVCC connections at each end of the chip.
• Minimize the current loop from each of the outputs through the ferrite bead filter and back to GND. The size of this current loop determines its effectiveness as an antenna.
• Grounding — The PVCC decoupling capacitors should connect to GND. All ground should be connected at the IC GND, which should be used as a central ground connection or star ground for the TPA3126D2.
• Output filter — The ferrite EMI filter (see Figure 31) should be placed as close to the output terminals as possible for the best EMI performance. The LC filter should be placed close to the outputs. The capacitors used in both the ferrite and LC filters should be grounded.

For an example layout, see the TPA3126D2 Evaluation Module (TPA3126D2EVM) User Guide (SLOU506). Both the EVM user manual and the thermal pad application reports, SLMA002 and SLMA004, are available on the TI Web site at http://www.ti.com.