12.1 Layout Guidelines

Class-D switching edges are fast and switched currents are high, therefore the user must take care when planning the layout of the printed-circuit board. The following suggestions will help to meet audio, thermal, and EMC requirements:

• TAS5729MD uses the PCB for heat sinking; therefore, the PowerPAD must 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 TAS5729MD a 1-µF high-quality ceramic capacitor is used. Large (10 μF or greater) bulk power supply decoupling capacitors should be placed near the TAS5729MD on the PVDD supply.
• Keep the current loop from each of the outputs through the output inductor and the small filter capacitor 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 TAS5729MD PowerPAD should be connected to GND.
• Crosstalk: it is recommended to have a width separation between analog traces, like headphone input or outputs, to avoid possible crosstalk.
• 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 should be grounded.

The EVM product folder 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 59. TAS5729MD Layout Example