12.1 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.

• uses the PCB for heat sinking therefore the powerPad needs to be soldered to the PCB and adequate copper area and copper vias connecting the top, bottom and internal layers should be used.
• Decoupling capacitors: the high-frequency decoupling capacitors should be placed as close to the supply pins as possible; on the a 1-µF high-quality ceramic capacitor is used. Large (10μ-F or greater) bulk power supply decoupling capacitors should be placed near the 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.
• To avoid crosstalk issues on the headphone/line driver output, it is recommended to have a wide space between the traces of the outputs.
• Grounding: A big common GND plane is recommended. The PVDD decoupling capacitors should connect to GND. The TAS5721 PowerPAD 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 EVM product folder (http://www.ti.com/tool/tas5721evm) and User’s Guide available on www.ti.com shows schematic, bill of material, gerber files and more detailed layout plots.

12.2 Layout Example

Figure 82. Layout Recommendation