13.1 Layout Guidelines
Class-D switching edges are fast and switched 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.
- Decoupling capacitors: the high-frequency decoupling capacitors must be placed as close to the supply pins as possible; on the TAS5755M a 1-µF high-quality ceramic capacitor is used. Large (10 μF or greater) bulk power supply decoupling capacitors must be placed near the TAS5755M on the PVDD supplies.
- 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 must connect to GND. The TAS5755M PowerPAD must be connected to GND.
- Output filter: remember to select inductors that can handle the high short circuit current of the device. The LC filter must be placed close to the outputs.
The EVM product folder (TAS5755EVM) and User’s Guide (SLOU481A) available on www.ti.com show schematic, bill of material, gerber files, and more detailed layout plots.