INMP441 Omnidirection Microphone Module

INMP441 Omnidirection Microphone Module

Omnidirectional Mini Digital I2S Mems 24Bit Adc High Sensitivity Low Power ESP32

     The INMP441 Omnidirection Microphone Module is an omnidirectional (picks up sound from all directions) MEMS microphone board that converts sound to digital internally and gives a 24 bit I2S digital output. The board carries the TDK InvenSense INMP441 microphone chip. It operates between 1.8V - 3.3V and draws about 1.4mA. Its signal-to-noise ratio is 61dBA and sensitivity -26dBFS; it gives a flat frequency response between 60Hz - 15kHz.

     Since the microphone has its own analog-to-digital converter, filters and I2S interface, no separate preamplifier, ADC or audio codec is needed: the sound reaches a controller board with I2S input directly as digital data. The cable interference and hum seen with analog microphone modules are greatly reduced. The board has 6 pins: SCK, WS, L/R, SD, VDD and GND; the L/R pin selects whether the microphone sends data in the left or right channel, so two modules can work in stereo on the same I2S bus.

     The round board of about 14mm diameter fits small device housings. It is suitable for voice command and voice assistant devices, speech recognition, sound recording, decibel measurement and noise monitoring. If sound output is needed in the same project, it can be used together with an I2S input amplifier module (e.g. MAX98357).

Key features:

     Digital I2S output: Sound is converted to 24 bit digital data inside the microphone and sent over the I2S bus. No separate ADC, preamplifier or codec is needed; interference and hum on an analog cable line are greatly reduced.

     Omnidirectional pickup: The microphone picks up sound from all directions; recording and voice command detection continue even if the speaker's direction changes.

     Clean sound: 61dBA signal-to-noise ratio, -26dBFS sensitivity and a flat 60Hz - 15kHz frequency response capture speech clearly; the -75dBFS PSR value reduces supply line noise mixing into the sound.

     Stereo use: With the L/R pin tied to GND the microphone sends data in the left channel, tied to 3.3V in the right channel. Two modules connected to the same SCK, WS and SD lines record in stereo.

     Low consumption: It draws about 1.4mA from a 1.8V - 3.3V supply; this gives long operating time in battery powered audio devices.

Features:

• Product type: Omnidirectional MEMS microphone module with I2S digital output
• Chip: INMP441 (TDK InvenSense)
• Output: I2S digital, 24 bit
• Operating voltage: DC 1.8V - 3.3V
• Current: approx. 1.4mA
• Signal-to-noise ratio (SNR): 61dBA
• Sensitivity: -26dBFS (at 94dB SPL)
• Frequency response: 60Hz - 15kHz (flat)
• Power supply rejection (PSR): -75dBFS
• Directivity: Omnidirectional
• Sample rate: approx. 8kHz - 48kHz
• Channel select: L/R pin (GND: left channel, 3.3V: right channel)
• Pins: SCK (bit clock), WS (word select), L/R (channel select), SD (data output), VDD, GND
• Pin pitch: 2.54mm, 6 pins
• Operating temperature: -40°C - 85°C (chip value)
• Colour: Black board
• Dimensions: approx. 14mm diameter (round board with two half-round notches)
• Weight: approx. 1gr

Usage information:

• Connect VDD to the 3.3V output of the controller board and GND to ground. Connect SCK to the I2S bit clock (BCLK) pin of the board, WS to the word select (WS / LRCLK) pin and SD to the I2S data input. The controller board generates the clock signals; the microphone only sends data.
• Do not leave the L/R pin floating: with a single microphone tie it to GND and read the left channel. For stereo, connect the SCK, WS and SD pins of two modules together; tie the L/R pin of one to GND and the other to 3.3V.
• The microphone sends 24 bit data; set the I2S read on the controller board to a 32 bit frame, the audio data is in the upper 24 bits of the frame.
• The 6 pin male header comes unsoldered in the package; solder it to the board before use.

Application areas:

•  Voice assistant and voice command devices
•  Speech recognition and keyword detection
•  Sound recording devices
•  Decibel meters and sound level indicators
•  Noise monitoring and noise alarm systems
•  Baby monitors and listening devices
•  Intercom and doorbell audio line
•  Robot sound detection and turning towards sound
•  Toys and figures reacting to sound
   

Things to consider:

•  The supply is 3.3V at most. Do not apply 5V to the VDD pin; the microphone will be damaged.
•  The module has no analog audio output; it does not connect to the analog input (ADC) of a controller board. A board with I2S input is required (e.g. ESP32, Raspberry Pi Pico, STM32); Arduino Uno and Nano have no I2S interface.
•  Do not leave the L/R pin floating; the channel selection becomes undefined and there may be no sound or only hiss. With a single microphone tie it to GND.
•  If SCK and WS are swapped there is no sound or only hiss. Check the wiring by pin names and keep the I2S wires short.
•  While soldering, do not let flux, cleaning liquid or dust get onto the microphone chip and into its sound hole.

Package contents:

•  1 pcs INMP441 Omnidirection Microphone Module
•  1 pcs 6 pin male header (unsoldered)
•  Note: Controller board and connection cables are not included in the package.