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Multimedia codec has switchable speaker driver

Posted: 01 Feb 2007 ?? ?Print Version ?Bookmark and Share

Keywords:mobile TV? Wi-Fi? codec? Wolfson? speaker?

WM8991 audio codec from Wolfson

Wolfson Microelectronics plc has announced the WM8991 audio codec featuring a dual mode, 1W speaker driver with the flexibility to switch between Class AB and Class D operation. The WM8991 is based on Wolfson's Audio Hub concept, which is enabling a new generation of feature-rich multimedia handsets that can mix and select from multiple audio sources including voice, radio, music, mobile TV and Wi-Fi.

Offered in compact 5-by-5mm BGA packaging and with 98dB SNR performance, the WM8991 supports the signal switching, audio conversion and voice mixing requirements for next-generation mobile phones, allowing designers to add new features quickly and enabling flexible new end-user modes such as viewing TV during a voice call. The digital core consumes less power than similar devices and can be as low as 5mW during a voice call.

Filterless Class D
The innovative ability to select Class AB or Class D operation allows handset designers to deploy filterless Class D technology into a wider range of increasingly diverse handheld form factors where restrictions such as noise and interference previously demanded a Class AB driver topology. System designers may select the most appropriate mode of operation for the anticipated usage scenario, allowing battery life for the end user to be maximized.

Eight analog inputs and nine pop-free analog outputs eliminate the need for external input or output switches. This means designers can quickly integrate a second processor, such as the digital TV tuner, without tri-stating the main processor interface. All line-in and line-out ports are fully balanced and feature differential signaling, allowing high-speed cellular handsets to deliver high performance, noise-free audio. GPIOs permit designers to implement button or accessory detect with programmable button debounce to support handset differentiating features, as well as added-value capabilities such as processor wake-up from low-power sleep mode. There is also a dedicated MIC BIAS input pin supporting eight programmable current detect levels for enhanced accessory support.

Space, BOM savings
The WM8991 features a fully differential headphone output, which eliminates external capacitors to save more space and minimize the BOM, reduce noise and crosstalk and improve bass quality. Phantom ground design, as well as the provision of an AC coupled mode, allows the headphone output to drive an additional ear speaker.

Advanced voice features include digital sidetone, allowing low frequency noise, such as wind noise and mechanical vibration, to be digitally filtered from the attenuated voice feedback signal.

The WM8991 is available for sampling today.

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