September 19, 2008
LMV1088
Dual Input, Clarisound
TM
Far Field Noise Suppression
Microphone Amplifier with Automatic Calibration Ability
General Description
The LMV1088 amplifies near-field voice signals within 4cm of
the microphones while rejecting far-field acoustic noise
greater than 0.5m from the microphones. Up to 20dB of far-
field rejection is possible in a properly configured and cali-
brated system.
Part of the Powerwise® family of energy efficient solutions,
the LMV1088 consumes 1mA of supply current while provid-
ing superior performance to DSP solutions consuming over
10 times the power.
A fast calibration during the manufacturing test process al-
lows the LMV1088 to compensate the entire microphone
system. This calibration includes mismatch in microphone
gain and frequency response, as well as acoustical path vari-
ances. The LMV1088 stores the calibration coefficients in on-
board EEPROM. The calibration is initiated by I2C command
or by pin control.
The dual microphone inputs are differential to provide excel-
lent noise immunity. The microphones are biased with an
internal low-noise bias supply.
Key Specifications
(3.3V supply, unless otherwise specified)
■
Supply voltage 2.7V to 5.5V
■
Supply current 1mA (typ)
■
Signal to noise ratio (A-weighted) 60dB (typ)
■
Total harmonic distortion 0.1% (typ)
■
Noise cancellation 20dB (typ)
■
PSRR 85dB (typ)
Features
■
Low power consumption
■
No added processing delay
■
Automatic Calibration
■
Space-saving 36 Bump micro SMD package
■
Up to 20dB SNRI
Applications
■
Mobile handsets
■
Mobile and handheld two-way radios
■
Bluetooth and other powered headsets
■
Hand-held voice microphones
■
Portable public address systems
Application of the LMV1088
20213029
PowerWise® is a registered trademark of National Semiconductor Corporation.
© 2008 National Semiconductor Corporation 202130 www.national.com
LMV1088 Dual Input, Clarisound
TM
Far Field Noise Suppression Microphone Amplifier with
Automatic Calibration Ability
