The terms wearable technology, wearables and fashion electronics describe smart electronic devices that are worn close to or on the surface of the skin, where they detect, analyze, and transmit information concerning e.g. body signals such as vital signs, and/or ambient data and in some cases allows immediate biofeedback to the wearer.
Wearable technology has a variety of applications which has grown as the field itself expands. It appears prominently in consumer electronics with the popularization of smartwatches and fitness trackers, smart glasses, and smart headphones. Apart from commercial uses, wearable technology is being incorporated into navigation systems, advanced textiles, and healthcare.
With the impact of COVID-19, the demand for wearable devices has increased, which is accelerating the growth of the market globally.
Today’s wearable devices are designed to be more functional and fancier for a better user experience. These improvements demand greater CPU processing power for digital signal processing such as voice recognition. This causes an increase in CPU processing current, which adversely affects the battery life. Renesas’ wearable devices solution is designed to solve this problem.
The “heart” of this solution is our RE01, which is one of the world’s most energy efficient MCUs with an Arm® Cortex® M Core implemented on Silicon on Thin Buried Oxide (SOTBTM). With the SOTB process technology, we achieved ultra-low current consumption in both active and standby mode, and high-speed CPU operation (64MHz) at a low voltage (1.62V), which is impossible to achieve with conventional bulk silicon processes. RE01 obtained the world-class ULP-CP benchmark 705 certified by EEMBC.
In addition, by using an external ultra-low Iq DC/DC buck regulator, ISL9123, RE CPU processing current can be reduced by half 25µA/MHz→12µA/MHz, which contributes to the extension of battery life while adding processing of heavy-load sensor data. Application notes are available for more information: D6004358 and D6004480.
The sensors on this wearable device solution are critical. Light sensor ISL29125 is a low power, high sensitivity, RED, GREEN and BLUE color light sensor (RGB) with an IR blocking filter. Color sensing improves the look and feel of wearable devices, such as smartwatches; and also controls the back light depending on ambient light conditions, from the blue light of a sunny day to the yellow or red tinge of some indoor lighting. An application note is available for more information. HS3001 is a highly accurate, fully-calibrated relative humidity and temperature sensor. The high accuracy, fast measurement response time, and long-term stability, along with the small package size, make the HS3001 ideal for wearable devices.
To transmit detected data from the sensors, such as vital signs and ambient data, we are using the RL78/G1D Bluetooth® low energy microcontroller, which enables immediate biofeedback to the wearer. RL78/G1D microcontrollers support Bluetooth® low energy and achieve the lowest level of current consumption in the industry at 4.3 mA RF transmission current (0 dBm output) and 3.5 mA RF receiving current. Since the antenna is built in, it simplifies the circuit design and reduces the design cost for customers.
With this solution, Renesas is showing engineers a compact, energy efficient, and robust design for wearable devices.
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