July 8, 2011
PDM Output Pre-Amplifier for Electret Microphones
The LMV1022 and LMV1023 integrate a pre-amplifier and
ADC that can be mounted inside an electret condenser mi-
crophone (ECM). The digital output signal is a pulse density
modulation (PDM) bitstream that alows the microphone to
connect directly to the DSP or baseband processor.
Part of National Semiconductor’s Powerwise™ family of prod-
ucts, the LMV1022/LMV1023 consume 900µW of power dur-
ing operation, offering significant power savings over an
analog microphone with an external ADC. The LMV1022 out-
puts its data on the rising clock edge. The LMV1023 outputs
its data on the falling clock edge. Both devices can share the
same clock and data lines to create a 4-wire stereo solution.
The external clock frequency sets the audio pass band fre-
quency. An 800kHz clock sets the pass band to 7kHz. A
2.4MHz clock sets the pass band to 20kHz.
The LMV1022 and LMV1023 are available in 6-bump micro
SMD packages with 1kg adhesion properties.
(Typical VDD = 1.8V, CLOCK = 1.2MHz, fINPUT = 1kHz,
VINPUT = 18mVPP, unless otherwise specified)
■ SNR A-weighted
■ Analog A-weighted noise floor
■ Supply current
■ Total harmonic distortion
■ Power supply rejection ratio
■ Integrated 21 dB Pre-Amp and ADC for significant power
and space savings
■ Integrated high-pass Filter to reduce 'Plop Noise'
■ Excellent RF immunity (e.g. buzz noise)
■ LMV1022 and LMV1023 combine to create 4-wire Stereo
■ Very thin 0.35mm micro SMD packaging
■ Adhesion technology >1kg
■ Digital audio subsystems and stereo arrays
■ Electret condenser microphones with all digital output
■ Portable communications and small form factor devices
■ Digital audio computing or voice security
■ Automotive or array systems
■ Headphone and headset accessories
For a stereo application, see STEREO OPERATION in the Application Section.
© 2011 National Semiconductor Corporation 202124
202124 Version 2 Revision 1 Print Date/Time: 2011/07/08 14:36:52