MLX90640 — 32x24 Pixel FIR Thermal Imaging Camera Array

Overview

The MLX90640 is a 768-pixel ( $32 \times 24$ ) Far-Infrared (FIR) thermopile thermal imaging camera sensor array manufactured by Melexis. Mounted in a 4-pin TO-39 metal can package, it converts infrared radiation from objects in its field of view into real-time 2D thermal heat maps.

Measuring non-contact surface temperatures from $-40^\circ\text{C}$ to $+300^\circ\text{C}$ with a target accuracy of $\pm 1.0^\circ\text{C}$ , the MLX90640 comes in two FOV lens options:

MLX90640-BAB: $55^\circ \times 35^\circ$ narrow Field of View (telephoto lens).
MLX90640-BAA: $110^\circ \times 75^\circ$ wide Field of View (wide angle lens).

Communicating over $I^2C$ (0x33 default) at speeds up to 1.0 MHz (Fast-Mode Plus), it supports programmable frame refresh rates from $0.5\text{ Hz}$ up to $64\text{ Hz}$ .

Quick reference


Operating voltage (`VIN`)	3.3 V to 5.0 V DC (breakout module with 3.3V LDO regulator)
IC supply voltage (`VDD`)	3.0 V to 3.6 V DC (3.3 V nominal)
Interface	$I^2C$ Fast-Mode Plus (up to 1.0 MHz)
Default $I^2C$ address	`0x33`
Thermal array resolution	768 pixels ( $32 \text{ Columns} \times 24 \text{ Rows}$ )
Object temperature range	$-40^\circ\text{C}\text{ to }+300^\circ\text{C}$
FOV Lens Variants	BAB: $55^\circ \times 35^\circ$ / BAA: $110^\circ \times 75^\circ$
Programmable refresh rate	0.5 Hz, 1 Hz, 2 Hz, 4 Hz, 8 Hz, 16 Hz, 32 Hz, 64 Hz
Active current	$23.0\text{ mA}$ continuous sampling

Pinout (TO-39 Metal Can & Breakout Header)

text

        ┌───────────────────┐
        │  [TO-39 Metal Can]│
        │   (Infrared Lens) │
        └─┬───┬───┬───┬─────┘
         VIN GND SCL SDA
          1   2   3   4

Pin	Name	Type	Description
1	`VIN`	Power	Supply power input (+3.3 V to +5.0 V DC)
2	`GND`	Power	Ground reference (0 V)
3	`SCL`	Digital Input	$I^2C$ Serial Clock (up to 1 MHz)
4	`SDA`	Digital Input / Output	$I^2C$ Serial Data

Specifications

Parameter	Symbol	Min	Typ	Max	Unit	Conditions
Supply Voltage (Module)	$V_{VIN}$	3.3	3.3 / 5.0	5.5	V	Power rail with LDO
Active Supply Current	$I_{CC}$	—	23.0	28.0	mA	Continuous sampling state
Target Temp Accuracy	$T_{acc}$	-1.0	$\pm 1.0$	+1.0	°C	Within $0^\circ\text{C} \dots 100^\circ\text{C}$ range
Noise Equivalent Temp (NETD)	$NETD$	—	0.1	0.25	K	At $1\text{ Hz}$ refresh rate
Storage EEPROM Size	$EEPROM$	—	832	—	Words	On-chip factory calibration matrix

Thermal Frame Refresh & $I^2C$ Bandwidth Requirements

Each frame requires reading 832 words (1,664 bytes) of RAM telemetry over $I^2C$ , plus applying complex factory EEPROM calibration calculations (Stefan-Boltzmann radiation equations).

At $f_{SCL} = 100\text{ kHz}$ , max achievable frame rate is $\sim 0.5\text{ Hz}$ to $1\text{ Hz}$ .
At $f_{SCL} = 400\text{ kHz}$ / $1.0\text{ MHz}$ , frame rates of 8 Hz to 16 Hz are achievable on 32-bit MCUs (ESP32, Teensy 4.0).

Wiring

MLX90640 Pin	ESP32	Teensy 4.0	Notes
`VIN`	3.3V	3.3V	Power rail
`GND`	GND	GND	System ground
`SCL`	GPIO 22	Pin 19 (SCL0)	Requires 400kHz/1MHz $I^2C$ clock
`SDA`	GPIO 21	Pin 18 (SDA0)	$I^2C$ Data

Important

RAM Memory Requirements for MCUs: Processing MLX90640 EEPROM calibration matrices and pixel calculations requires $>20\text{ KB}$ of dynamic RAM. Traditional 8-bit microcontrollers (such as the Arduino ATmega328P with 2KB SRAM) cannot run the MLX90640 driver library. Use 32-bit ARM or ESP32 microcontrollers.

Example (Adafruit_MLX90640 Library)

cpp

#include <Wire.h>
#include <Adafruit_MLX90640.h>

Adafruit_MLX90640 mlx;
float frame[768]; // Buffer for 32x24 thermal pixel grid

void setup() {
  Serial.begin(115200);
  Wire.begin();
  Wire.setClock(400000); // Set I2C clock to 400 kHz

  Serial.println("Adafruit MLX90640 Thermal Camera Test");

  if (!mlx.begin(MLX90640_I2CADDR_DEFAULT, &Wire)) {
    Serial.println("MLX90640 not found! Check I2C wiring.");
    while (1);
  }

  mlx.setMode(MLX90640_CHESS);
  mlx.setResolution(MLX90640_ADC_18BIT);
  mlx.setRefreshRate(MLX90640_2_HZ); // 2 Hz refresh rate
}

void loop() {
  if (mlx.getFrame(frame) == 0) {
    // Print center pixel temperature (row 12, col 16)
    float centerTemp = frame[12 * 32 + 16];

    Serial.print("Center Target Temp: ");
    Serial.print(centerTemp);
    Serial.println(" °C");
  }

  delay(500);
}

Common mistakes

Attempting to run on 8-bit Arduino boards: The MLX90640 API requires large float buffers and heavy matrix math. Use 32-bit microcontrollers.
Using 100 kHz standard $I^2C$ speed: Operating at 100 kHz causes frame buffer reading to stall for over 200 ms per frame. Increase $I^2C$ bus clock to 400 kHz or 1 MHz in code (Wire.setClock(400000)).

Notes

MLX90640 vs AMG8833 vs MLX90614: MLX90640 provides 768 pixels ( $32 \times 24$ thermal image); AMG8833 provides 64 pixels ( $8 \times 8$ Grid-EYE); MLX90614 is a single-pixel thermometer.

Interface	I2C (Fast-Mode Plus up to 1MHz)
Supply	3–3.6 V
Package	4-pin TO-39 Metal Can / Breakout Board (Qwiic / STEMMA QT)