The WM8904 from Cirrus Logic features a ground reference headphone amplifier with a dual mode charge pump construction

     Cirrus Logic's WM8904 is a high performance, ultra-low power stereo codec featuring a stereo ground reference headphone amplifier combined with a dual mode charge pump architecture to optimize efficiency and power consumption during playback. The ground reference headphone and wire output eliminate AC coupling capacitance, and both outputs include a common-mode feedback path to suppress ground noise. Control sequences for audio path Settings can be pre-loaded and executed by an integrated control write sequencer to reduce software driver development and minimize pops and clicks.

     The analog input stage can be configured as single-ended or differential input. Up to three stereo microphones or wire inputs can be connected. The input impedance is constant in the PGA gain setting. A stereo digital microphone interface with two input options is provided.

     Dynamic Range Controller (DRC) provides compression and level control to support a wide range of portable recording applications. The anti-clip and quick-release features provide superior performance in the presence of loud pulse noise. ReTune Mobile 5-band parametric equalizer is integrated with fully programmable coefficients to optimize speaker characteristics. Programmable dynamic range control is also available for maximum volume, protecting the speaker from clips and preventing premature shutdown due to battery sagging.