INMP441 I2S microphone: specs and pinout
Omnidirectional MEMS microphone with a 24-bit I2S digital output, on a breakout board. The data sheet describes the bare chip, not the breakout.
Specs
| Spec | Value | Source |
|---|---|---|
| Supply voltage (VDD) | 1.62 V to 3.63 V (pin description: 1.8 V to 3.3 V) | source Table 1 Electrical Characteristics; Table 6 pin 7 |
| Supply current, normal mode | 1.4 mA typ at VDD = 1.8 V; 2.2 mA typ at VDD = 3.3 V | source Table 1 Electrical Characteristics |
| Interface | I2S, 24-bit, slave serial data port; SD output | source Features; Table 6 |
| Sensitivity | -26 dBFS typ (-29 to -23 dBFS) at 1 kHz, 94 dB SPL | source Table 1 |
| Signal-to-noise ratio | 61 dBA typ (20 Hz to 20 kHz, A-weighted) | source Table 1 |
| Frequency response | -3 dB points at 60 Hz and 15 kHz | source Table 1 |
| Maximum acoustic input | 120 dB SPL peak | source Table 1 |
| SCK frequency / WS frequency | 0.5 to 3.2 MHz / 7.8 to 50 kHz | source Table 3 Serial Data Port Timing Specifications |
| Start-up time | 218 clock cycles after power-up (85 ms with SCK at 3.072 MHz) | source Theory of Operation, Power Management, Startup |
| Operating temperature (biased) | -40 C to +85 C | source Table 4 Absolute Maximum Ratings |
Power
| Value | Source | |
|---|---|---|
| Supply | 1.62 V to 3.63 V | source Table 1 Electrical Characteristics |
| Current | 1.4 mA at 1.8 V, 2.2 mA at 3.3 V (normal mode) | source Table 1 Electrical Characteristics |
Chip pins
These are the pins of the chip on the module, from the chip datasheet. The module's own header may label or expose them differently.
These are the chip's 9 pins. The breakout board (header order, regulator, pull-ups, any 5 V tolerance) is not covered by an official document.
| Pin | Function | Voltage | Notes | Source |
|---|---|---|---|---|
| 1 | SCK | Serial-data clock for I2S interface | source Table 6 Pin Function Descriptions (chip pins, bottom view) | |
| 2 | SD | Serial-data output for I2S interface; tri-states when not driving; the sheet recommends a 100 k pulldown on the SD trace | source Table 6 Pin Function Descriptions (chip pins, bottom view) | |
| 3 | WS | Serial data-word select for I2S interface | source Table 6 Pin Function Descriptions (chip pins, bottom view) | |
| 4 | L/R | Left/right channel select: low = left, high = right | source Table 6 Pin Function Descriptions (chip pins, bottom view) | |
| 5 | GND | Ground | source Table 6 Pin Function Descriptions (chip pins, bottom view) | |
| 6 | GND | Ground | source Table 6 Pin Function Descriptions (chip pins, bottom view) | |
| 7 | VDD | Power, 1.8 V to 3.3 V; decouple to pin 6 with a 0.1 uF capacitor | source Table 6 Pin Function Descriptions (chip pins, bottom view) | |
| 8 | CHIPEN | Microphone enable: low = disabled/power-down, high = enabled | source Table 6 Pin Function Descriptions (chip pins, bottom view) | |
| 9 | GND | Ground | source Table 6 Pin Function Descriptions (chip pins, bottom view) |
Build with it
Project ideas for the INMP441 I2S microphone. Each link opens Soldr with the prompt filled in; Soldr assigns the pins, checks power and shows how to wire every part.
- Sound level meter on an OLED: The ESP32 has I2S interfaces and runs at 3.3 V, inside the microphone's 1.62-3.63 V range. The 24-bit samples are processed in software.
- Clap switch for an LED: A loud peak in the sample stream triggers the LED. The microphone's 120 dB SPL peak limit is far above a clap at a desk.
- Short voice clip recorder: I2S clock of 0.5-3.2 MHz and word-select of 7.8-50 kHz give audio sample rates a microSD writer can keep up with. Tell anyone being recorded and get their consent.
- Microphone to speaker loopback: Both the microphone and the amplifier are I2S devices, so audio stays digital until the amplifier. Keep the speaker away from the microphone to avoid feedback squeal.
Common mistakes
- Powering the chip from 5 V: the supply rating is 1.62-3.63 V and the absolute maximum on VDD is 3.63 V (source: link, Table 1 and Table 4). Whether the breakout has a regulator is not in any official document
- Leaving L/R unset: L/R low puts the signal in the left channel of the I2S frame, high puts it in the right channel, so a master reading the other channel gets silence (source: link, Table 6 pin 4)
- Leaving CHIPEN low: CHIPEN low puts the microphone in power-down mode; it must be high (VDD) to run (source: link, Table 6 pin 8)
Not covered by the official source
- Values are from the a hosted copy of the maker's document (rev 1.0).
- Breakout board layout, regulator and 5 V tolerance are not documented by any official source.
- Supply current values are from page 4 of the datasheet.
Sources
- link (InvenSense INMP441 data sheet DS-INMP441-00 rev 1.0, 02/06/2014)