MLX90615 | GUILCOR SENSORS

MLX90615
Temperature sensors

Compact non-contact infrared temperature sensor designed for embedded systems and space-constrained applications.

Maximum precision
+/- 0,2°K

Minimum temperature
-40°C

Maximum temperature
+115°C

Resolution
0,02°C

Power supply voltage

3,0→3,6V

Response time

0,1s

Typical current
1,5 mA

Price
Medium

What is a MLX90615 sensor ?

The MLX90615 is a compact digital infrared sensor designed for non-contact temperature measurement, both of objects and living beings.

It follows the principle of the MLX90614 but comes in a package that is twice as small, with a limited range, making it ideal for:

portable medical thermometers,
embedded systems with limited space,
smart consumer products (watches, wearables, IoT).

Operating principle

The MLX90615 detects the infrared radiation emitted by an object via an integrated thermopile.

The signal is amplified, digitized, and compensated for by an internal DSP processor that corrects for ambient temperature effects.

Internal formula:

T_objet = (RawIR x 0,02) - 273,15

💡 The calculation includes automatic compensation for ambient temperature via the internal sensor.

Example of digital conversion (I²C)

Register (hex)	Description	Resolution
0x26	Ambient temperature	0,02 °C / LSB
0x27	Object temperature	0,02 °C / LSB
0x20	Emissivity (adjustable)	0xFFFF = 1,0
0x2E	I²C Address	Programmable (EEPROM)

T(°C) = (value x 0,02) - 273,15

Principle diagram (I²C connection)

+3.3V
 │
[MLX90615]
 │ SDA ───────┐
 │ SCL ───────┤── [I²C Microcontroller]
 │ GND

💡 Default I²C address: 0x5B.

Application areas

🏥 Medical thermometers (forehead, ear)

🧠 Connected devices and health watches

🏠 Home automation: thermal detection, HVAC

⚙️ Embedded electronics and autonomous robots

🧪 Contactless measurement on sensitive surfaces

Should I choose a MLX90615 sensor ?

Strengths points

🎯 High precision in the human range (0–60 °C)
→ Ideal for precise medical and environmental measurements.
🧱 Format miniature (TO-46)
→ Integrates easily into compact and portable designs.
⚡ Quick response (0.1 s)
→ Optimized sensor for dynamic body temperature detection.
🔋 Low consumption
→ Only 1.5 mA in operation — perfect for battery-powered systems.

Weaknesses points

🌡️ Limited measurement range
→ Inappropriate for high temperatures (>115 °C).
📏 Fixed field of view (~35°)
→ Non-configurable, unlike some versions of the MLX90614.
💨 Sensitive to dust and condensation
→ The IR lens must remain clean to maintain accuracy.

Useful information

Here is some useful information regarding the MLX90615 sensors.

Main registers (I²C – 0x5B)

Adress (hex)	Name	Description
0x20	Emissivity	Adjust the emissivity constant
0x26	Tambient	Internal temperature
0x27	Tobject	Target object temperature
0x2E	I²C Address	Programmable address
0x2F	Config Register	Operating mode and frequency
0x10	PWM Output	PWM output configuration

I²C Reading Example (pseudo-code)

i2c_start();
i2c_write(0x5B << 1);
i2c_write(0x27);
i2c_start();
i2c_write((0x5B << 1) | 1);
LSB = i2c_read_ack();
MSB = i2c_read_nack();
i2c_stop();

raw = (MSB << 8) | LSB;
tempC = (raw * 0.02) - 273.15;

✅ Example:

Gross value = 16000 → Temperature = 46.85 °C

Typical integration diagram

3.3V ───────────┐ │ [MLX90615] │ SDA ───────┐ │ SCL ───────┤── MCU (Arduino, STM32, ESP32…) │ GND

💡 Add a 100 nF decoupling capacitor between VCC and GND for stability.

Setting of emissivity (register 0x20)