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MEMS mics deliver high-fidelity audio playback

Posted: 28 Apr 2010 ?? ?Print Version ?Bookmark and Share

Keywords:MEMS? MEMS mic? sensor? amplifier?

ADMP404/5 MEMS mic

Analog Devices Inc. has developed MEMS microphones that enable advanced audio functions for portable electronics including high-fidelity audio/video playback, hands free communication, and voice recognition with built-in wind noise suppression, and TIA-920-compliance for VoIP applications.

The new ADMP404 and ADMP405 iMEMS microphones combine ADI's audio signal processing expertise with its innovative patented and patent-pending iMEMS technology. The resulting MEMS microphones offer 62dB A-weighted SNR and 70dBV PSRR (power supply rejection ratio) with integrated high-pass filtering.

The devices enable end-product manufacturers to develop portable electronic devices that deliver clearer, more intelligible voice quality without the background noise/hiss produced by other microphones with lower SNR. The ADMP404 and ADMP405 are available in a small and thin 3.35mm x 2.5mm x 0.88mm surface-mount package that is reflow-solder-compatible with no sensitivity degradation. The ADMP404 and ADMP405 are halide-free.

Delivering a flat wideband frequency response from 100Hz to 15kHz on the ADMP404 and from 200Hz to 15kHz on the ADMP405, these new MEMS microphones eliminate the need for hardware filtering or advanced signal processing to enhance audio acquisition. The ADMP405, with a 200Hz roll-off, enables engineers to filter wind noise or fan noise energy at the transducer; this provides a clearer audio signal that can be more easily conditioned with any downstream signal processing. Engineers can now move beyond simple command and control voice recognition to full voice recognition for hands-free, translator and dictation applications.

The ADMP404 is a high-quality, low-cost, low-power, analog output bottom-ported omnidirectional MEMS microphone. It consists of MEMS microphone element, impedance converter and output amplifier. The ADMP404 sensitivity of -38dBV makes it a suitable choice for both near-field and far-field applications. Low power consumption enables long battery life for portable applications. A built-in particle filter provides high reliability. The ADMP404 complies with the TIA-920 Telecommunications Telephone Terminal Equipment Transmission Requirements for Wideband Digital Wireline Telephones standard.

Additionally, the ADMP405 combines these attributes with a specially designed low-frequency 200Hz roll-off that will reduce wind noise. Capabilities offered by the ADMP404 and ADMP405 enhance near-field and far-field performance while simplifying power supply design requirements and providing designers with significantly more flexibility in board layout.

"There's a growing recognition by system designers that poor microphone performance at the front end significantly increases requirements for downstream audio processing. This leads to higher power consumption, higher cost and a more complex system design," said Mark Martin, VP, MEMS/sensor group, ADI. "By leveraging ADI's proven iMEMS and audio signal processing technologies, these new MEMS microphones simplify designs and enable many new high-performance capabilities for portable consumer and industrial products."

The ADMP404 and ADMP405 iMEMS microphones are now sampling with volume production scheduled for June 2010. Pricing is $1.79 per unit in 1,000-unit quantities.

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