The temperature sensor reference design for wearable devices features 0.13°C accuracy and a versatile USB form-factor PCB.
Temperature sensors in wearable devices are crucial in enhancing functionality and user experience. They are essential for health monitoring, providing continuous updates on body temperature that can indicate health changes, such as infections. These sensors also aid in fitness and wellness by helping users optimize their physical activities based on body heat data. Additionally, they improve safety and comfort by adjusting device operations in response to ambient temperatures, thus preventing discomfort and potential health risks. Overall, the integration of temperature sensors significantly elevates the capabilities of wearable technology, making it more adaptive and responsive to both environmental conditions and individual health needs. TIDA-00452 is a temperature sensor reference design from Texas Instruments (TI) developed explicitly for wearable devices.
The reference design highlights the LMT70 temperature sensor, optimized for the wearables market. With its 0.13°C accuracy at human body temperatures, the LMT70 is particularly suitable for wearable devices. Its compact WCSP package enables quick heating and rapid thermal response when in contact with human skin.
The design features a USB form-factor PCB board with breakout tabs for attaching various substrates. The included design guide details the thermal response of these substrates as well as calibration techniques for the MSP430F5528 ADC.
The reference design is suitable for both industrial and personal electronics applications. The offerings include an application processor module, an electronic thermometer, a probe board, and a wearable fitness and activity monitor for industrial use. In the realm of personal electronics, the selection features a dashboard camera, a GPS personal navigation device, smart trackers, and a smartwatch.
The LMT70 used in this design is an analogue output temperature sensor with high accuracy, and an output enable switch. It can detect temperatures ranging from -55°C to 150°C and offers an accuracy of +/—0.13°C at 30°C. This precision makes it particularly suitable for medical and wearable devices like body monitors and fitness watches.
In this design, the LMT70EVM was utilized to record the LMT70’s output voltage across various substrates. The EVM includes the LMT70 mounted on a USB form factor board breakout tab. This breakout tab can be detached, allowing users to attach wires or headers to the exposed copper pads for conducting remote temperature measurements. Additionally, the EVM is equipped with an MSP430F5548 microcontroller, which captures the output voltage from the LMT70 through its integrated ADC.
TI has tested this reference design. It comes with a Bill of Material (BOM), schematics, assembly drawing, Printed Circuit Board (PCB) layout, and more. The company’s website has additional data about the reference design. To read more about this reference design, click here.
