The device features stereo ground-referenced headphone amplifiers using the Cirrus Logic ‘Class-W’ amplifier techniques - incorporating an innovative dual-mode charge pump architecture - to optimize efficiency and power consumption during playback. The ground-referenced headphone and line outputs eliminate AC coupling capacitors, and both outputs include common mode feedback paths to reject ground noise.

Control sequences for audio path setup can be pre-loaded and executed by an integrated control write sequencer to reduce software driver development and minimize pops and clicks via Cirrus Logic’s SilentSwitch™ technology.

The analog input stage can be configured for single ended, or differential inputs. Up to three stereo microphone or line inputs may be connected. The input impedance is constant with PGA gain setting.

A stereo digital microphone interface is provided, with a choice of two inputs.

A dynamic range controller provides compression and level control to support a wide range of portable recording applications. Anti-clip and quick release features offer excellent performance in the presence of loud impulsive noises.

ReTune™ Mobile 5-band parametric equalizer with fully programmable coefficients is integrated for optimization of speaker characteristics. Programmable dynamic range control is also available for maximizing loudness, protecting speakers from clipping and preventing premature shutdown due to battery droop.

Common audio sampling frequencies are supported from a wide range of external clocks, either directly or generated via the FLL. The WM8904 can operate directly from a single 1.8V switched supply. For optimal power consumption, the digital core can be operated from a 1.0V supply.