MEMS microphones target high-fidelity audio playback

April 23, 2010 // Julien Happich

Analog Devices has created two new MEMS microphones that enable advanced audio functions for portable electronics. These functions include 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 ADMP 404 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 the industry's highest SNR (signal-to-noise ratio) of 62 dB A-weighted and the highest PSRR (power supply rejection ratio) of 70 dBV with integrated high-pass filtering, claims the manufacturer. End-product manufacturers can now develop portable electronic devices that deliver clearer, more intelligible voice quality without the background noise/hiss produced by other microphones with lower SNR.

Delivering a flat wideband frequency response from 100Hz to 15kHz on the ADMP404 and from 200Hz to 15kHz on the ADMP405, these MEMS microphones eliminate the need for hardware filtering or advanced signal processing to enhance audio acquisition.

The ADMP405 with a 200 Hz roll-off is the industry's first with this capability, enabling 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. The ADMP404 consists of a MEMS microphone element, an impedance converter, and an output amplifier. The ADMP404 sensitivity of -38 dBV makes it an excellent choice for both near-field and far-field applications.

The ADMP404 has a high SNR of 62 dB A-weighted and flat, wideband frequency response from 100 Hz to 15 kHz, resulting in natural sound with high intelligibility. 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 200 Hz roll-off that will reduce wind noise.

Capabilities offered by the ADMP404 and ADMP405 dramatically enhance near-field and far-field performance while simplifying power supply design requirements and providing designers with significantly more flexibility in board layout.  ADI also offers a full portfolio of high performance audio codecs, class D amplifiers and processors to complete the audio signal chain.

The ADMP404 and ADMP405 iMEMS microphones are now sampling with volume production scheduled for June 2010. The ADMP404 and ADMP405 are available in a small and thin 3.35x2.50x0.88mm surface-mount package that is reflow-solder-compatible with no sensitivity degradation. The ADMP404 and ADMP405 are halide-free.

More information at www.analog.com/pr/mic

Learn more about Analog Devices' iMEMS Technology at www.analog.com/pr/iMEMS

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