ActLight lowers heart-rate sensor power

April 27, 2017 // By Peter Clarke
ActLight lowers heart-rate sensor power
ActLight SA (Lausanne, Switzerland) has developed a heart-rate sensor based on dynamic photodiode (DPD) technology that consumes about 20 percent of the power of commercial devices.

As the heart-rate sensor consumes about 80 percent of the power in smartwatches and fitness wearables the technlogy is expected to gain design wins in that area. ActLight is a fabless chip company that licenses out its DPD Intellectual Property (IP) and provides design and technical support services to its customers.

The DPD technology is similar to the avalanche photodiode in performance but has no need for an amplifier and it works at an operation voltage of about 1V, compatible with standard CMOS. In addition, the DPD typically measures time to triggering instead of the amplitude of an output photocurrent which makes for an easier to obtain digital value.

Typically, wearables use photoplethysmography (PPG) to measure pulse and oxygen uptake in the blood by measuring the amount of light reflected back from blood flowing in an artery. But that bright light, needed to make adequate measurements is a major power drain. By using the DPD technology it should be possible to reduce the light power required by 80 percent, ActLight said.

The sensor has been developed with École polytechnique fédérale de Lausanne (EPFL) and an unnamed global semiconductor vendor with experience in the medical technology sector. Already tested and calibrated, ActLight's heartrate sensor is ready to be produced in large series to equip next generation wearables.

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