LMV1024/LMV1026 (Stereo)

PDM Output with Pre-Amplifier for Electret Microphones

General Description

National’s LMV1024 and LMV1026 stereo amplifiers are

solutions for the new generation of voice enrichment capa-

bilities. National has integrated sigma delta modulation and

analog cores to improve the voice quality and the perfor-

mance and to support designer’s choices.

Each 20 kHz preamplifier drives a Pulse Density Modulated

(PDM) signal at an over sampled 60 bit stream, offering

versatility. These solutions provide immediate conversion to

high performance audio spectrum, thus completing a high

quality audio system. The LMV1024 and LMV1026 operate

from 1.6V to 3V.

National’s new adjustable clock frequency technology is de-

signed for stereo, performance and ease of use. The stereo

function is either a rising or falling edge clock command. The

high drive, robust PDM signal directly from an ECM (Electret

Condenser Microphone), upgrades existing lower quality,

low-level signal constraints.

These advanced mixed signal preamplifiers cleanly, accu-

rately and creatively eliminate older, poorer quality systems,

which restricted performance and versatility. The 4-wire

PDM signaling reduces RF noise and simplifies layout. Us-

ing National’s PDM solutions is the choice for higher quality

mono or stereo and multi-array applications.

National’s 518uA circuits deliver stereo portability with audio

quality bandwidth. These solutions enable rapid system

evaluation and enhance consumer satisfaction. National pro-

vides the LMV1024 and LMV1026 in 6-bump micro SMD

packages with 1 kg adhesion properties.

Features

(Typical V

V

n

Enhanced high-performance, full PDM output from the

element

n

Stereo chipset and array routing

n

SNR A-weighted

59 dB

n

Digital A-weighted noise floor

−89 dBFS

n

Supply current

518 µA

n

Clock frequency

400 kHz to 2.4 MHz

n

Total harmonic distortion

0.03%

n

Power supply rejection ratio

100 dB

n

n

Highly integrated stereo or mono signaling

n

Maximized system performance

n

Reduced components and layout

n

RF (buzz noise) managed with 4 wire signaling

n

Thinnest 0.35 mm micro SMD packaging

Applications

n

Digital output audio subsystems and stereo arrays

n

Electret condenser microphones with all digital output

n

Portable communications and small form factor

n

Digital audio computing or voice security

n

Automotive or array systems

n

Headphone and Headset accessories

Typical Application

20133475

For a stereo application, see STEREO OPERATION in the Application Section.

November 2005

© 2005 National Semiconductor Corporation

DS201334

www.national.com