11.4 Interfacing with Class D Audio Output

The Audio Class D (CLASSD) amplifier is a digital input, Pulse Width Modulated (PWM) output mono Class D amplifier. It features a high-quality interpolation filter embedding a digitally-controlled gain, an equalizer and a de-emphasis filter.

On its input side, the CLASSD is compatible with most common audio data rates. On the output side, its PWM output can drive either:

  • high-impedance single-ended or differential output loads (Audio DAC application), or
  • external MOSFETs through an integrated non-overlapping circuit (Class D power amplifier application).
Figure 11-5. Class D Interface Example Schematic