Overview

The MLX90614 is a non-contact infrared thermometer IC manufactured by Melexis. It integrates an IR thermopile detector chip, a custom signal-conditioning ASSP with a 17-bit ADC, and a powerful DSP unit inside a TO-39 metal can package.

It measures two distinct temperatures simultaneously: Ambient temperature (TAT_A) of the package die, and Object surface temperature (TOT_O) of a target body placed in its field of view without making physical contact (from −70∘C-70^\circ\text{C} up to +380∘C+380^\circ\text{C}).

Quick reference

Operating Voltage (VCC)3.0 V to 3.6 V DC (3 V variant MLX90614ESF-Bxx) / 4.5 V to 5.5 V DC (5 V variant MLX90614ESF-Axx)
Object Temp Range−70∘C-70^\circ\text{C} to +380∘C+380^\circ\text{C}
Ambient Temp Range−40∘C-40^\circ\text{C} to +125∘C+125^\circ\text{C}
Accuracy±0.5 ∘C\pm 0.5\text{ }^\circ\text{C} around room/body temp (0∘C to +50∘C0^\circ\text{C} \text{ to } +50^\circ\text{C})
Resolution0.02 ∘C0.02\text{ }^\circ\text{C} output step resolution
Field of View (FOV)90∘90^\circ standard (AAA variant) / 35∘35^\circ narrow angle (DCC medical variant)
Communication protocol2-wire SMBus (I2C compatible, fixed default slave address 0x5A)

Pinout

Standard 4-Pin TO-39 Package & GY-906 Breakout Board

text
           ┌──────────┐
           │ MLX90614 │
           └──────────┘
            │  │  │  │
            1  2  3  4
PinNameTypeDescription
1SCL / VNKDigital InputSMBus Clock line (or PWM output line)
2SDA / PWMDigital I/OSMBus Data line (open-drain, requires pull-up resistor)
3VDD / VCCPowerSupply voltage (+3.3 V or +5.0 V depending on chip suffix)
4VSS / GNDPowerGround (0 V)

Specifications

ParameterSymbolMinTypMaxUnitConditions
Supply Voltage (5V variant)VDDV_{DD}4.55.05.5VMLX90614ESF-AAA
Supply Voltage (3V variant)VDDV_{DD}3.03.33.6VMLX90614ESF-BAA
Operating Supply CurrentIDDI_{DD}—1.52.5mAActive SMBus mode
Medical Accuracy (Body temp)ΔTmed\Delta T_{med}-0.2±0.1\pm 0.1+0.2°CTobj=36∘C to 38∘CT_{obj} = 36^\circ\text{C} \text{ to } 38^\circ\text{C} (DCC variant)
Output ResolutionRESRES—0.02—°C17-bit ADC output
Refresh Ratefrefreshf_{refresh}0.010.5512HzEEPROM programmable

SMBus Temperature Read Register & Math

Temperature data is stored as a 16-bit raw integer (RAWRAW) in RAM registers:

  • 0x06: Read Ambient Temperature (TAT_A).
  • 0x07: Read Object 1 Temperature (TO1T_{O1}).

Conversion Formula to Kelvin and Celsius

T (in Kelvin)=RAW×0.02 KT\text{ (in Kelvin)} = RAW \times 0.02\text{ K}

T (in ∘C)=(RAW×0.02)−273.15T\text{ (in }^\circ\text{C}) = (RAW \times 0.02) - 273.15

For example, a raw reading of 0x3AF2 (1509015090 decimal):

T=(15090×0.02)−273.15=301.80 K−273.15=+28.65 ∘CT = (15090 \times 0.02) - 273.15 = 301.80\text{ K} - 273.15 = +28.65\text{ }^\circ\text{C}

Wiring

GY-906 (MLX90614) Pin→Microcontroller (Arduino Uno / ESP32)Notes
VIN / VCC3.3V or 5V (Check breakout LDO)Check if breakout features LDO regulator
GNDGNDGround
SCLSCL (A5 on Uno, GPIO22 on ESP32)4.7 kΩ4.7\text{ k}\Omega pull-up resistor to VCC recommended
SDASDA (A4 on Uno, GPIO21 on ESP32)4.7 kΩ4.7\text{ k}\Omega pull-up resistor to VCC recommended

Common mistakes

  • Mixing 3V and 5V part numbers: The MLX90614ESF-AAA is a 5V-only part, whereas the MLX90614ESF-BAA is a 3.3V-only part. Feeding 5V to a 3.3V chip without a breakout board LDO will destroy it.
  • SMBus repeated start requirement: The MLX90614 requires I2C Repeated Start (Wire.endTransmission(false)) between writing the register address and reading the 2-byte word + PEC byte response. Standard I2C stop conditions cause SMBus NACK errors.
  • Field of View (FOV) distance errors: The standard 90∘90^\circ FOV sees a wide cone. Measuring a small object (e.g. human forehead) from >5 cm>5\text{ cm} away averages the object's temperature with the surrounding wall/background temperature. Place the sensor 1 to 3 cm1\text{ to }3\text{ cm} from the target.

Notes

  • Includes an 8-bit Packet Error Code (PEC) CRC byte at the end of SMBus readings for high-reliability industrial sensing.

Assets & downloads