New tiny zero-power temperature sensor extends the battery life of wearable devices

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temperature sensor

Researchers create a temperature sensor that runs on only 113 picowatts of power. This sensor extends the battery life of wearable devices that monitor health, smart home systems, IoT, and environmental monitoring systems.

Our new zero-power technology could one day eliminate the need to ever change or recharge a battery, said, Patrick Mercier, professor at UC San Diego Jacobs School of Engineering.

Their new approach involves minimizing power in two domains, current source and conversion of temperature to a digital readout. Researchers built an ultra-low power current source using “gate leakage” transistors.

Gate leakage is considered problematic in systems such as micro-processors or precision analog circuits. Many researchers are trying to get rid of leakage current, but exploiting it to build an ultra-low power current source.

conventional process

Using these current sources, researchers developed a less power-hungry way to digitize temperature. This process normally requires passing current through a resistor, its resistance changes with temperature, then measuring the resulting voltage, and then converting that voltage to its corresponding temperature using a high-power analog to digital converter.

Instead of this conventional process, researchers developed an innovative system to digitize temperature directly and save power.

As the temperature changes, the system adapts the temperature-dependent current source charges in the same amount of time as the fixed current source. A built-in digital feedback loop equalizes the charging time by reconnecting the temperature-dependent current source to a capacitor of a different size the size of this capacitor is directly proportional to the actual temperature.

The temperature sensor integrated into a small chip measuring 0.15 × 0.15 square millimeters in the area. It operates at temperatures ranging from minus 20 C to 40 C.

The sensor has a response time, approximately one temperature update per second, which is slightly slower than existing temperature sensors. However, this response time is sufficient for devices that operate in the human body, and other environments where temperature do not fluctuate rapidly.

Moving forward, the team is working to improve the accuracy of the temperature sensor.

More information: [nature]

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