Omnidirectional Microphone with

Bottom Port and Digital Output

ADMP421

Rev. 0

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FEATURES

Small and thin 3 mm × 4 mm × 1 mm surface-mount package

High SNR of 61 dBA

High sensitivity of −26 dBFS

Flat frequency response from 100 Hz to 15 kHz

Low current consumption: <650 μA

High PSRR of 80 dBFS

Fourth-order Σ-Δ modulator

Digital PDM output

Compatible with Sn/Pb and Pb-free solder processes

RoHS/WEEE compliant

APPLICATIONS

Smartphones and feature phones

Digital video cameras

Bluetooth headsets

Video phones

Teleconferencing systems

GENERAL DESCRIPTION

The ADMP421 is a low cost, low power, digital output bottom-

ported omnidirectional MEMS microphone. The ADMP421

consists of a MEMS microphone element, an impedance converter

amplifier, and a fourth-order Σ-Δ modulator. The digital inter-

face allows for the pulse density modulated (PDM) output of

two microphones to be time multiplexed on a single data line

using a single clock.

The ADMP421 has a high SNR and high sensitivity, making it

an excellent choice for far field applications. The ADMP421 has

a flat wideband frequency response resulting in natural sound

with high intelligibility. Low current consumption and a sleep

mode enable long battery life for portable applications. A built-

in particle filter provides high reliability. The ADMP421 complies

with the TIA-920 Telecommunications Telephone Terminal

Equipment Transmission Requirements for Wideband Digital

Wireline Telephones standard.

The ADMP421 is available in a thin 3 mm × 4 mm × 1 mm

surface-mount package. It is reflow solder compatible with no

sensitivity degradation. The ADMP421 is halide free.

FUNCTIONAL BLOCK DIAGRAM

ASIC

DATA

L/R SELECT

CLK

GND

MEMS

MEMBRANE

BACKPLATE

IMPEDANCE

CONVERTER

ADC

ADMP421

Figure 1.