Audio codec extends playback time in portables

Wolfson Microelectronics has announced an ultra-low-power audio codec designed to dramatically extend playback time for audio enabled portable devices, such as portable media players, multimedia handsets and handheld gaming systems. According to the company, the WM8903 will enable designers to create portable devices with playback times up to 40 hours on a single charge of a 300-mAh battery.

The WM8903 features several new technologies, including the company's 'Class W' adaptive headphone amplifier technology, SmartDAC low-power DAC capacitor switching architecture, and SilentSwitch pop/click suppression technology. The stereo ground-referenced headphone amplifier – based on an evolution of class G and H technology – intelligently tracks the actual music signal level and uses an adaptive dual-drive charge pump to optimize power dissipation.

SmartDAC enables DAC-to-headphone power consumption of only 4.4 mW and includes a capability for programmable “performance vs. power” profiles, allowing system designers to optimize for each usage scenario. SilentSwitch integrates an output clamp that holds the headphone output at ground during system power up, an integrated sequencer to simplify register programming, and a DC servo to control DC offset through the signal path.

In addition, when in record mode, the WM8903 implements an advanced dynamic range controller (DRC) featuring a feed-forward design, automatic level control, peak limiter, and a user programmable transfer function, attack and delay. A quick release impulse noise filter enhances the intelligibility of recorded sound in the presence of loud impulse noises by precisely recognizing the difference between sudden, unwanted noises and actual rises in the desired signal being recorded.

The WM8903 can operate from a common 1.8-V supply for both analog and digital power rails, or, for optimal power consumption, the digital supply can operate at 1.2 V. In addition, the WM8903 can share noisy power supply rails with other digital devices with no performance compromise.

The WM8903 is available for sampling now in a thin 40-pin, 5 x 5 x 0.55-mm QFN package, and priced at $1.80 per unit in volumes of 10,000 units.

Wolfson Microelectronics , +44 (0) 131 272 7000,

Product literature:
WM8903 information page
WM8903 datasheet (PDF)

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