10.1 Layout Guidelines
The TPA3116D2 can be used with a small, inexpensive ferrite bead output filter for most applications. However, since the class-D switching edges are fast, it is necessary to take care when planning the layout of the printed circuit board. The following suggestions will help 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 TPA3116D2 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.
- Keep the current loop from each of the outputs through the ferrite bead and the small filter cap and back to GND as small and tight as possible. 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 TPA3116D2.
- Output filter — The ferrite EMI filter (see Figure 35) 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 TPA3116D2 Evaluation Module (TPA3116D2EVM) User Guide (SLOU336). 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.
10.3 Heat Sink Used on the EVM
The heat sink (part number ATS-TI 10 OP-521-C1-R1) used on the EVM is an 14x25x50 mm extruded aluminum heat sink with three fins (see drawing below). For additional information on the heat sink, go to www.qats.com.
Figure 42. EVM Heatsink
This size heat sink has shown to be sufficient for continuous output power. The crest factor of music and having airflow will lower the requirement for the heat sink size and smaller types can be used.