Wolfson Loads Audio Codec With Functionality

Edinburgh, UK — Wolfson Microelectronics plc launched the first mono codec in a new series addressing all of the major digital still and video camera audio requirements on a single chip, in response to growing demand for high-quality sound in portable, digital recording and camera equipment.

The Wolfson WM8974 is a low-power, feature-rich codec and is the first in a series of products to be coming from Wolfson targeting digital still cameras and digital-voice recording applications.

The WM8974 features a digital signal processing (DSP) core that provides a wind-noise filter to improve audio recording during video-recording mode, a five-band equalizer to improve audio output and a programmable notch filter to reduce motor noise. The WM8974 also includes an integrated phase-locked loop (PLL) supporting a wide operating frequency range from 12 to 19 MHz. The device supports a differential or single-ended microphone complemented by the microphone pre-amp and automatic level control (ALC), followed by an output stage where the drivers for speakers and headphones are included to reduce component count in the final system. With the support of up to 5 V, the speaker driver is capable of driving an industry-leading speaker output of up to 900 mW.

The WM8974 operates at power supplies as low as 2.5 V and consumes less then 10 mA during 48-kHz playback, and operates on 1.62 V in standby.

“Digital still cameras are increasingly differentiated by their audio capabilities and Wolfson is releasing a series of compact, high performance, affordable solutions that address this opportunity,” said Yan Goh, Wolfon's product marketing manager.

The WM8974 is available now in a 4mm x 4mm QFN package at $2.04 in 10,000-piece quantities.

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Traditionally, Wolfson has developed platform-type products that support a broad range of portable and non-portable consumer audio applications. Today, Wolfson has decided to zero in on specific portable applications when they can identify a market of sufficient size with specific requirements in terms of a feature set and performance.

Consequently, Wolfson's latest device, the WM8974 mono audio codec intended for digital still cameras (DSC) and digital-voice recording applications, such as dictaphones, was conceived.

The DSC market, which is growing 30% to 40% annually, is expected to reach approximately 80 million units worldwide this year, according to market analysts.

Now that the DSC market has evolved to the point that it has, Wolfson has seized the opportunity to produce a codec specifically designed for this application, with a lot of functionality, as opposed to using a common platform product, said John Crawford, product marketing engineer for portable products.

Wolfson's highly integrated WM8974 codec offers many technology improvements over its previous-generation codecs, Crawford said.

The new codecs, for instance, are being offered in a 4mm x 4mm QFP, compared to the 5mm x 5mm QFP, Crawford said.

Utilizing a new DSP core enabled the company to reduce the die size and develop an enhanced feature set, Crawford said. This also contributed to reduced power consumption. The system requirements for the DSC market also allowed a slightly reduced number of I/Os, which helped support a smaller package, he said.

Additionally, the company has achieved a 10% to 20% performance improvement on the digital-to-analog converter (D/A converter) side with signal-to-noise ratio (SNR) in the current product offering 98 dB playback, compared to its previous generation products, which offered dBs of around 89 to 90, Crawford said. “This technology improvement enables the camera to capture a wider scope of sound that is clearer,” he said.

Wolfson's new DSP core provides high sound quality benefits such as noise reduction, Crawford said. The wind noise filter feature reduces the sound of wind when recording outside on a windy day, for example. A programmable notch filter reduces motor noise by preventing the camera from picking up the motor noise caused by the lens moving in and out when using the zoom capability. And, despite its tiny size, the chip includes a five-band graphic equalizer to play back small video music clips, Crawford said.

Despite drawing low power, the WM8974 codec can still drive really load speakers. Speaker output power has increased to 900 mW, compared to 500 mW in the previous generation products, Crawford said.

Integrating the core function to include all of these special audio features will save design engineers from having to integrate these features onto the codec themselves, Crawford said.

This device is the first in a suite of codec products that will follow, Crawford said. Next the company plans to target smartphones, PDAs and DVD players.

Other players in the audio codec arena include Texas Instruments, National Semiconductor and Philips Semiconductor.

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