Melexis launches miniature infrared temperature sensor for smart wearables
Melexis has introduced the MLX90636, an ultra-miniature, contactless infrared temperature sensor designed to bring high-accuracy thermal sensing to next-generation wearable health devices. Measuring just 1.8 × 1.8 × 0.75 mm, the sensor delivers an accuracy of ±0.2°C across the human body temperature range, making it suitable for integration into space-constrained products such as smartwatches, fitness bands and smart rings.
Building on the success of the MLX90632, the MLX90636 advances surface-mount device (SMD) far-infrared (FIR) temperature sensing, providing wearable manufacturers with a compact, low-power solution for continuous temperature monitoring.
Alongside the launch, Melexis is progressing research into wrist-to-core temperature modelling. Using data from MLX90636 sensors integrated into wrist-worn devices, the research aims to explore how skin temperature measurements could be used to estimate core body temperature (CBT), potentially enabling more advanced digital health monitoring.
Advancing infrared temperature sensing for compact wearables
As wearable technology evolves beyond basic activity tracking towards more sophisticated health monitoring, demand is increasing for accurate, non-contact temperature measurement in smaller devices.
Traditional contact-based temperature sensors can be affected by ambient temperature fluctuations and thermal lag, potentially limiting measurement consistency. SMD FIR thermometry offers an alternative by measuring infrared radiation emitted from the skin surface, enabling contactless temperature sensing in compact wearable designs.
Developing a high-precision FIR sensor in an ultra-miniature package presents significant thermal management challenges. The MLX90636 is designed to deliver stable, accurate measurements while maintaining robustness against rapid changes in ambient temperature and air turbulence.
Key features and technical specifications of the MLX90636 include:
Ultra-compact package: Measuring just 1.8 × 1.8 × 0.75 mm, the chip-scale package is designed for integration into space-constrained smartwatches, fitness bands and smart rings.
High measurement accuracy: Factory-calibrated to deliver ±0.2°C accuracy across the human body temperature range.
Low-power operation: Sleep current below 2.5 µA, with programmable refresh rates from 0.5 Hz to 32 Hz, supporting battery-powered wearable applications.
Flexible system integration: Supports dual 2.8 V or 3.3 V supply lines and an I²C interface with a software-definable address pin.
Calibration and software support: Includes integrated post-calibration options and access to open-source driver support through GitHub.
From wrist temperature monitoring to core body temperature estimation
The MLX90636’s combination of high accuracy and extreme miniaturisation provides wearable manufacturers with a hardware platform for developing more advanced temperature-monitoring applications.
However, measuring skin temperature at the wrist is not the same as measuring core body temperature. Wrist temperature can be influenced by several factors, including local blood flow, ambient conditions and heat generated by the wearable device itself.
To address this challenge, Melexis is researching wrist-to-core temperature modelling to investigate how data from MLX90636 sensors could support the estimation of core body temperature in wearable digital health devices.
As part of this work, Melexis is finalising an evaluation kit to help assess the feasibility and performance of core body temperature estimation using wrist-based sensor inputs.
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