10.1 Layout Guidelines
The TAS576xM can be used with a small, inexpensive ferrite bead output filter when speaker are placed with short internal wires and supply voltages are 12 V or lower, for systems with longer wires or higher than 12V supply voltage LC filtering is recommended.
Class-D switching edges are fast and swithced currents are high so it is necessary to take care when planning the layout of the printed circuit board. The following suggestions will help to meet audio, thermal and EMC requirements
- TAS576xM uses the PCB for heatsinking therefore the powerPad need to be soldered to the PCB and adquate cobber area and cobber via's connecting the top, bottom and internal layers should be used.
- Decoupling capacitors — The high-frequency decoupling capacitors should be placed as close to the PVDD and AVCC pins as possible, on the TAS576xM a 1-µF high-quality ceramic capacitor is used. Large (470 μF or greater) bulk power supply decoupling capacitors should be placed near the TAS576xM on the PVDD supplies. Local, high-frequency bypass capacitors should be placed as close to the DVDD, AVDD and CPVDD pins as possible.
- Keep the current loop from each of the outputs through the output inductor 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 — A big common GND plane is recommended. The PVDD decoupling capacitors should connect to GND. The TAS576xM power pad should be connected to GND
- Output filter — remember to select inductors that can handle the high short circuit current of the device. The LC filter should be placed close to the outputs. The capacitors used in both the ferrite and LC filters should be grounded
The EVM user guide available on www.ti.com shows both schematic, bill of material and more detailed layout plots including gerber files.