Codec optimises mobile audio power drain

Ultra-low-power codec extends playback time for audio enabled portable devices, such as portable media players, multimedia handsets and handheld gaming systems.

The WM8903 codec is the first of a new generation of ultra-low-power audio devices from Wolfson Microelectronics.

The codec is designed to dramatically extend playback time for audio enabled portable devices, such as portable media players, multimedia handsets and handheld gaming systems.

The WM8903 ultra-low-power codec delivers Wolfson high-performance audio and market-leading power consumption in an ultraslim low-profile form factor to meet the demanding needs of today's multimedia portable devices.

The WM8903 enables designers to push product design boundaries and develop compelling, highly differentiated end products.

The WM8903 features Wolfson's new SmartDAC technology, a low-power DAC capacitor switching architecture.

This enables DAC to headphone power consumption of just 4.4mW and includes a capability for programmable "performance/power" profiles, allowing system designers to optimise for each usage scenario, such as docked or on the move.

The WM8903 also includes Wolfson's Class W amplifier technology, an evolution of class G/H, featuring an adaptive dual drive charge pump and DC servo circuit architecture.

The Class W headphone amplifier technology intelligently tracks the actual music signal level and uses an adaptive dual drive charge pump to optimise power dissipation.

The WM8903 can also operate from a common 1.8V supply for both analogue and digital power rails.

With a significant power supply rejection ratio (PSRR), the WM8903 can share noisy power supply rails with other digital devices with no performance compromise.

This architecture not only optimises power consumption but also eliminates the need for large DC blocking headphone capacitors, enabling significant savings in PCB space and the audio subsystem bill of materials.

It also brings additional audio benefits through an improved bass response.

The WM8903 further enhances the audio performance by integrating Wolfson's innovative SilentSwitch technology that extends its pop and click suppression capability, by incorporating sophisticated clamp and sequencer circuitry.

Unwanted noise at the headphone amplifier output is reduced during power-up and mute/un-mute by clamping the output to ground.

Using an integrated sequencer with programmable delay times to power-up/power-down parts of the WM8903 reduces pops and clicks significantly and reduces time to market by lowering software driver development time.

When in record mode the WM8903 implements an advanced dynamic range controller (DRC) which optimises recorded sound quality.

Wolfson has also implemented a quick-release impulse noise filter that enhances the intelligibility of recorded sound in the presence of loud impulse noises.

This noise filter can precisely recognise the difference between sudden, unwanted noises and actual rises in the desired signal being recorded.

The WM8903 provides the core for a distributed ultra low power audio subsystem.

Its inherent flexibility offers the system designer the option to use the latest digital output microphones, such as Wolfson True Mics technology, through an integrated digital microphone interface.

This is complimented by six highly configurable analogue inputs for stereo microphone recording, as well as connection to a variety of analogue audio sources.

Additional audio outputs also allow seamless connection with efficient Class D speaker amplifiers, such as Wolfson's WM9001 (launched earlier this year), in portable media platforms, which require speakers.

Peter Frith, CTO at Wolfson comments: "The WM8903 is truly a next generation ultra low power device, enabling a remarkable extension in device audio playback time".

"With the WM8903, designers can create portable devices with playback times up to 40 hours on a single charge".

"The WM8903 is packed with innovative new technologies and is a great example of the Wolfson AudioPlus product line, interlacing elements of Pure Audio, Smart Power, True Mics and Enhanced Soundware".

The WM8903 is available for sampling now in an ultrathin 40-pin 5 x 5 x 0.55mm QFN package, ideal for space constrained, portable applications.

WM8903 customer evaluation boards with the Wolfson Interactive Setup and Configuration Environment (WISCE) are available to enable very rapid device evaluation and development.

The WISCE software provides an interactive register map interface allowing control and overview of the device settings as well as outputting fully commented C-code.

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