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Digital MEMS microphones boast advanced sound quality

Posted: 29 Apr 2011 ?? ?Print Version ?Bookmark and Share

Keywords:microphones? mobile phones? portable computers?

STMicroelectronics has launched the MP34DB01 and MP45DT02 MEMS microphones that enable enhanced audio experience in mobile phones and portable computers, as well as in many other existing and emerging applications with a voice input.

According to iSuppli, the market for MEMS microphones for consumer electronics and mobile handsets is forecast to grow revenue at a CAGR of 24 percent between 2009 and 2014. Driving factors include the breakthrough in the use of noise suppression requiring multiple microphones, as well as adoption of new consumer applications beyond handsets and laptops, such as slate tablets and gaming.

ST's MEMS microphones use acoustic sensor technology jointly developed with OMRON, temperature variations and electromagnetic interference, while providing audio signals. Integrating ST's electronic control circuit and OMRON's micro-machined sensor in a single package, the microphones deliver the audio performance at lower power consumption than traditional condenser (ECM) microphones.

In addition to the size, MEMS microphones enable advancements in sound quality, realized by incorporating multiple microphones in one device. Such microphone arrays, facilitated by the small form factor, sensitivity matching and frequency response of ST's microphones, enable the implementation of active noise and echo canceling, as well as beam-forming, a sound-processing technology that helps isolate a sound and its location. These features are important for cellphones and other devices, especially if they are used in noisy and uncontrollable environments.

Another important factor in multiple-microphone applications is the high temperature stability of MEMS microphones after reflow that ensures ample flexibility in placing the auxiliary microphones, including in locations with higher temperature excursions.

ST's MP34DB01 microphone claims to be the only device in the market with real high-fidelity audio bandwidth, delivering flat frequency response in the full audio band of 20C20,000Hz, coupled with advanced signal-to-noise ratio (62 dB) and power-supply noise rejection (70 dB).

Housed inside an ultra-small 3x4x1 mm package, the microphone is specifically designed for mobile phones, with the acoustic port hole placed on the bottom of the package. This layout enables phone manufacturers to mount the microphone on the backside of the cell-phone printed circuit board for slimmer designs and still obtain a short acoustic path from the environment to the microphone.

The other addition to ST's MEMS microphone family, the MP45DT02, is a top-port 3.76 x 4.72 x 1.25mm device that suits the size and sound-inlet position requirements of laptops and tablets. The microphone provides a 58 dB signal-to-noise ratio.

ST's bottom-port MP34DB01 MEMS microphone is available for volume shipping and the top-port MP45DT02 microphone will start mass production in Q2 2011.

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