Audio-capable portable devices (such as portable media players, multimedia phones) require a long audio playback time, which requires a long battery life. In order to make the battery life of the portable device long, on the one hand, improve the battery quality, and more importantly, the power consumption of the components used in the portable device is low. The battery life of a portable device is a function of system power and audio codec (CODEC) power and can be expressed as:
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Where K is the factor related to battery capacity, battery voltage and power converter efficiency, A is the system power consumption, and B is the audio CODEC power consumption. In order to maintain battery life under the premise of small and thin form factors, all components in the power and audio signal paths are required to reduce power consumption.
To this end, Wolfson Microelectronics has introduced a new generation of ultra-low-power audio CODEC WM8905, which greatly reduces the battery life of audio-enabled portable devices and extends audio playback time by up to 40 hours.
WM8903 ultra low power CODEC
The WM8903 function box is shown in Figure 1. Its features are as follows:
　　
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Figure 1 WM8903 functional block diagram
SmartDACTM Technology—This is a unique low-power DAC switch architecture that allows DAC-to-earphone power consumption of only 4.4 milliwatts. The ability to programmatically adjust the “performance and output power†curve allows system designers to optimize each Usage (in different states, such as connection or movement).
Class W amplifier technology—an adaptive dual drive charge pump and DC servo chip architecture. Class W headphone amplifiers intelligently track actual music signal levels and use an adaptive dual-driver charge pump to optimize power consumption. This architecture not only optimizes power consumption, but also eliminates the need for large DC blocking headphone capacitors, which greatly saves PCB space and BOM of the audio subsystem. Audio performance is enhanced with improved bass response.
SilentSwitchTM technology—This technology minimizes “pops&clik†by integrating complex clamp and sequencer circuits.
Dynamic Range Controller—Using a “quick release†impulse noise filter to improve the resolution of the recorded sound and optimize the quality of the recorded sound in the presence of loud impulse noise.
Control Sequencer - Delay Time Programmable sequencer can turn on/off multiple units of the WM8903, significantly reducing "squeaky" and simplifying software driver development time.
Digital Microphone Interface - This interface provides high SNR (signal to noise ratio) and improved sensitivity matching.
application
The WM8903 is designed to significantly extend the playback time of audio-enabled portable devices and is used in portable audio applications, including PMP/MP3 players, multimedia handsets, handheld gaming systems, digital video cameras, and recorders. Figure 2 shows the application of the WM8903 in a portable media player.
　　
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Figure 2 Portable media player block diagram
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