Product category: Analogue and Mixed Signal ICs
News Release from: National Semiconductor | Subject: LMV1088
Edited by the Electronicstalk Editorial Team on 04 March 2008
Low-power amp suppresses microphone
noise
Dual-input microphone array amplifier reduces background noise and improves voice communication clarity in mobile phones, two-way radios and powered headsets.
New from National Semiconductor, the LMV1088 is the first in a line of audio products incorporating far-field noise suppression technology This novel technology delivers more natural-sounding voice quality by eliminating the output frequency distortions and other audio artefacts common with DSP or microprocessor software-based systems that use subband frequency processing algorithms to implement noise suppression
This article was originally published on Electronicstalk on 5 Jan 2001 at 8.00am (UK)
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The PowerWise LMV1088 dual-input microphone array amplifier reduces background noise and improves voice communication clarity in mobile phones, two-way radios and powered headsets.
Part of National's PowerWise energy-efficient family, the device consumes one-tenth the power (1mA) of comparable DSP or microprocessor software-based systems, setting a new standard for low power consumption.
The LMV1088 dramatically improves the talker's voice-signal/background-noise ratio in the communications system while retaining natural speech quality.
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The improvement directly translates to clearer voice signals on the receiving end of the communications link and an increase in customer satisfaction.
Additionally, the voice-signal/background-noise improvement allows increased accuracy by voice recognition systems since the background noise is not a significant part of the signal to discriminate against.
The LMV1088's continuous-time analogue processing provides instantaneous response to voice and background noise signals, unlike DSPs and processors which require extra computation time to adjust to voice background noise levels.
Additionally, the LMV1088's ease of use allows the rapid integration of noise suppression performance in phone handsets or powered headsets, without the added development time required to write and test voice-processing programming code for a DSP or microprocessor.
The LMV1088 is a dual-input microphone array amplifier offered in a miniature 3.5 x 3.5mm 36-bump micro SMDxt package.
The amplifier draws only 1mA of supply current.
It has a power supply rejection ratio (PSRR) of 85dB at 1kHz, with a typical signal/noise ratio (SNR) of 60dB and less than 1% total harmonic distortion plus noise (A-weighted THD+N).
The LMV1088 is designed for use with two microphones in an end-fire array configuration.
The microphones can be spaced in a line 15 to 25mm apart, or the equivalent acoustic path distance.
The optimal distance for the person speaking into the handset or headset microphone is 20 to 100m.
The amplifier's automatic calibration circuitry compensates for the microphones gain and frequency response variations, eliminating the need to use expensive matched microphone sets, while allowing flexible placement of the microphones in the final product.
The calibration data is stored in the LMV1088's internal EEPROM memory.
The calibration sequence chooses the optimised coefficients for the two microphones' spacing and acoustical environment.
The LMV1088 features four I2C compatible, selectable operating modes: default noise reduction, microphone 1 pass through, microphone 2 pass through or microphone 1 and 2 sum.
The LMV1088 is manufactured at National's wafer fabrication plant in South Portland, Maine, and tested and assembled at the company's facility in Melaka, Malaysia.
Available now, the LMV1088 is priced at US $9.95 each in 1000-unit quantities.
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