Technical Tips | Focusing on the new normal of sports and health, TI core technology helps the new trend of smart watches
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In recent years, with the continuous investment of mobile phone manufacturers, the smartwatch market has been full of vitality. In the first half of 2021, global smartwatch shipments exceeded 86Mu, a year-on-year increase of 32%. With the arrival of the peak season of the consumer market in the second half of the year, annual shipments are expected to exceed 200Mu. In the post-epidemic era when COVID-19 is raging around the world, smartwatches have been given a new mission, integrating blood oxygen, heart rate, ECG monitoring, body temperature, blood sugar, blood pressure monitoring and other functions that can reflect people's exercise status and health indicators . It has become a rigid demand. In the new normal of focusing on sports and health, how does TI Core Technology help and lead the new trend of smartwatches?
Generally, a smart watch with both sports and health management functions consists of several functional modules as shown in Figure 1. Today, we will mainly introduce TI's solutions for the two most popular functional modules: battery charging management and body temperature monitoring , aiming to help engineers provide the best device selection and reference design guidelines during project development.
Figure 1: Smartwatch system block diagram
1. Battery charging management
BQ25170: Linear charging IC, supports 1V, 4.2V, 4.35V, 4.4V multiple charging voltages, 30V maximum input withstand voltage, 800mA charging current, ultra-low 0.5uA battery leakage current, 2*2QFN ultra-small package.
Key highlights: The resistor configuration is simple and easy to use, and the high-voltage lithium battery provides long-lasting battery life.
Typical application circuit:
Figure 2: BQ25170 typical application circuit
The overall solution is only 9 mm2 ( 8 pins). Please refer to Figure 3 for the PCB layout.
Figure 3: BQ25170 Layout Example
BQ25180: Linear charger, supports multiple charging voltages from 5 to 4.65V, 25V maximum input withstand voltage, 1A charging current, ultra-low 10nA shipping mode, only 3uA battery leakage current, PowerPath & JEITA functions, 1.6*1.1mm WCSP ultra-small package.
Key highlights: Flexible I2C configuration, path management, shipping mode, and temperature adjustment are all available.
Typical application circuit:
Figure 4: BQ25180 typical application circuit
At the same time, BQ25180 also has the JEITA function that is ahead of similar products in the market, meeting the terminal product's requirements for temperature control during the charging process, which will bring users a safer, more reliable experience and protection.
Figure 5: Adjustable JEITA: -3 ~ 65°C
BQ25618/9: Switching charger, 5A charging current, Powerpath, integrated 1A Boost output, ultra-low 9uA battery leakage current, PowerPath & JEITA, 2.0*2.4mm WCSP & 4*4mm QFN ultra-small package.
Key highlights: I2C configuration, 1.5A efficient fast charging, integrated boost output.
Typical application circuit:
Figure 6: BQ25618 typical application circuit
2. Temperature monitoring
Smart watches with temperature monitoring functions were mentioned several years ago, but they did not attract much attention from the market. As COVID-19 swept the world, this function has attracted more and more attention from consumers. TI has been working in this field for many years, and its product catalog covers a variety of applications. The TMP117, which is the main product in the smart wearable market, has a temperature detection accuracy of up to 0.1°C.
TMP117: Up to 16-bit data conversion accuracy, +/-0.1℃ (-20oC to 50oC) medical temperature detection accuracy, digital output, built-in EEPROM without additional calibration, I2C temperature warning, 3.5uA@1Hz current consumption, 2*2WSON, 1*1.6WCSP ultra-small package.
Key highlights: ultra-high precision automatic calibration, ultra-low power consumption and ultra-small package.
Typical application circuit:
Figure 7: TMP117 typical application circuit
In body temperature monitoring, the biggest design challenge is how to transmit the temperature of the skin surface to the sensor as completely as possible to ensure the reliability of the detection results. TI has modeled and analyzed the heat conduction path of the watch under the human wrist and provided multiple application design guides for engineers to refer to, such as Layout design guides, FPC board reference design, etc., which can speed up the design process and easily solve the problem of inaccurate body temperature detection due to mechanical structure.
Figure 8: Heat conduction path (skin)
In addition, in the new normal context of smart watches focusing on sports and health, TI has launched a variety of cost-effective solutions for customers to choose from in power management, heart rate detection, blood oxygen detection, ECG measurement, ambient light detection and motor vibration functions .
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