MEMS for real: high-fidelity microphones

Analog Devices has created two 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 offer SNR (signal-to-noise ratio) of 62 dB A-weighted and PSRR (power supply rejection ratio) of 70 dBV with integrated high-pass filtering. The devices are available in a 3.35 mm × 2.50 mm × 0.88 mm surface-mount package that is reflow-solder-compatible with no sensitivity degradation. Both are halide-free.

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

The ADMP404 is an 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 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 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 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.