WM8903: Ultra low power CODEC for portable audio applications


The WM8903 is a high performance ultra-low power stereo CODEC optimised for portable audio applications. 

The device features stereo ground-referenced headphone amplifiers using the Wolfson ‘Class-W’ amplifier techniques - incorporating an innovative dual-mode charge pump architecture - to optimise efficiency and power consumption during playback. The ground-referenced outputs eliminate headphone coupling capacitors. Both headphone and line 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 sequencer to reduce software driver development and eliminate pops and clicks via Wolfson’s SilentSwitch™ technology. 

The analogue input stage can be configured for single ended, pseudo-differential or fully differential inputs. Up to 3 stereo microphone or line inputs may be connected. The input impedance is constant with PGA gain setting. 

A stereo digital microphone interface is provided, which can also be mixed with the mic/line signals at the output mixers. 

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 good performance in the presence of loud impulsive noises. 

Common audio sampling frequencies are supported from a range of external clocks, including 3MHz, 12MHz or 24MHz. 

The WM8903 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.


  • 4.5mW power consumption for DAC to headphone playback
  • DAC SNR 96dB typical, THD -86dB typical
  • ADC SNR 92dB typical, THD -80dB typical
  • Control sequencer for pop-free start-up and shut-down
  • Single register write for default start-up sequence
  • Stereo digital microphone input
  • 3 single ended inputs per stereo channel
  • 2 pseudo differential inputs per stereo channel
  • 1 fully differential mic input per stereo channel
  • Digital Dynamic Range Controller (compressor / limiter)
  • Digital sidetone mixing
  • Ground-referenced headphone driver
  • Ground-referenced line outputs
  • Stereo differential line driver for direct interface to WM9001 speaker driver
  • 40-pin 5x5mm QFN package