Analog Devices has developed two TIA-920 VoIP applications-compliant ADMP404 and ADMP405 MEMS microphones for providing enhanced audio functions in portable gadgets.
These functions include voice recognition with an in-built suppression of noise due to wind, hands-free communication and high-fidelity playback of video/audio . The ADMP404 is compliant with TIA-920 standard of Telecommunications Telephone Terminal Equipment Transmission Requirements for Wideband Digital Wireline Telephones.
These microphones are halide free and are available in surface-mount 3.35 mm × 2.50 mm × 0.88 mm packages. They are also reflow-solder compatible without sensitivity degradation. They simplify the requirements for the power supply design thus offering designers additional board layout flexibility. To complete the audio chain, ADI also provides a total range of high performing audio codecs, processors and class D amplifiers.
The ADM405 has a flat wideband response of 200 Hz–15 kHz, while the ADM404 has the response ranging from 100 Hz to 15 kHz, enabling these microphones to remove the requirement of enhanced signal processing or hardware-enabled filtering for improving audio acquisition. The ADM405’s 200 Hz roll-off capability is the first in the audio industry, which empowers engineers to filter out fan noise energy or wind noise at the transducer resulting in clearer audio signals. These signals can be conditioned easily through any downstream signal processing. It helps engineers to achieve complete voice recognition functionality for hands-free dictation and translation applications.
These microphones have integrated the audio signal processing expertise of ADI and its patent-pending and patented iMEMS technologies. They provide the highest signal-to-noise ratio (SNR) along with the highest power supply rejection ratio (PSRR) in the industry, besides an integrated high-pass filtering capability. The SNR is 62 dB A-weighted while the PSRR is 70 dBV. These capabilities will enable manufacturers of end-products to create portable electronic gadgets that are able to provide more intelligible and clearer voice quality, without the hiss or background noise created by lower-SNR microphones.
The low-power, low-cost, high-quality, analog output bottom-ported ADMP404 incorporates an MEMS microphone component, an audio output amplifier, and an impedance converter. It is a great option for far and near field applications due to its -38 dBV sensitivity. It also has high intelligibility and natural sound functionalities due to its high SNR. Its low power consumption feature renders longer battery life in portable applications. High reliability is ensured by an in-built particle type of filter.