This is a circuit of SA58672 Small Class-D Audio Amplifier. This circuit is suitable for mobile device. It  has maximum output power of 3.0 W  for a 4ohm load and 1.7W for 8ohm load with power supply of 5V. If we uses 3.6 V power supply, the maximum output power is 900mW with 8ohm load. Here is the circuit :

SA58672 Small Class D Audio Amplifier for Mobile Device circuit schematic

Using 9-bump Wafer Level Chip Scale Package (WLCSP), the SA58672UK save space in portable designs, because it measures only 1.66 x 1.71 x 0.6 mm.

This circuit produces better overall audio performance because it has improved RF rectification and immunity to noise. The SA58672UK  is suitable for cellular handsets or wireless and other portable audio application because it has fast start-up time of 7 ms eliminates pop-on sounds. [Source: NXP Application Note]