MEMS Microphones Enhance Audio Experience in MobilePhones and Portable Computers

STMicroelectronics today introduced two new digital MEMS microphones. Combining superior sound quality with robustness and reliability at reduced size and cost, ST’s MP34DB01 and MP45DT02 microphones 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% between 2009 and 2014. The driving factors include the breakthrough in the use of noise suppression requiring multiple microphones, as well as adoption in new consumer applications beyond handsets and laptops, such as slate tablets and gaming.
Picture: STMicroelectronics

ST’s MEMS microphones use best-in-class acoustic sensor technology jointly developed with Omron that is inherently less susceptible to mechanical vibration, temperature variations and electromagnetic interference, while providing high-fidelity reproduction of audio signals. Integrating ST’s electronic control circuit and Omrons’s micro-machined sensor in a single package, the microphones deliver superb audio performance at lower power consumption than traditional condenser (ECM) microphones. This optimized power consumption ensures longer battery life in portable devices for an extended user experience.

In addition to the size, robustness and energy economy advantages over ECM microphones, MEMS microphones enable dramatic advancements in sound quality, realized by incorporating multiple microphones in one device. Such microphone arrays, facilitated by the small form factor, superior sensitivity matching and frequency response of ST’s microphones, enable the implementation of active noise and echo cancelling, as well as beam-forming, a sound-processing technology that helps isolate a sound and its location. These features are valuable with the increasing use of cell phones and other devices 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 is the only device in the market with real high-fidelity audio bandwidth, delivering flat frequency response in the full audio band of 20–20,000 Hz, coupled with an unparalleled signal-to-noise ratio (62 dB) and power-supply noise rejection (70 dB).

Housed inside an ultra-small 3x4x1 mm package, the microphone has been 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 MP34DB01 has already been qualified by top-tier cell-phone makers and is now in mass production.

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 ideally suits the size and sound-inlet position requirements of laptops and tablets. The microphone provides an excellent signal-to-noise ratio (58 dB) and superior frequency response to alternatives for that market.

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