In recent years, various smart wearable devices have emerged. Among them, smart wristbands and wristwatches are more varied, but at the root of them, the core hardware principles are similar, and the sensor is an essential part. Below, the author will take stock of the sensors used in the current mainstream smart bracelets.
1. STMicroelectronics
Smart bracelets represent: å’•å’š smart bracelet, Fitbit Flex, bong, etc.
Sensor model: LIS3DH
STMicroelectronics has further expanded its line of motion sensor products with the introduction of the LS3DH, a low-power digital output 3-axis accelerometer that reduces power consumption by more than 90% compared to existing solutions in the market, while reducing package area and improving chip functionality.
With a minimum operating current consumption of 2μA, this 3x3x1 mm accelerometer is ideal for motion-sensing, space- and power-constrained applications such as cell phones, remote controls, and gaming consoles. With a full-scale range of ±2g/±4g/±8g/±16g, the LIS3DH provides very accurate measurement data output and maintains excellent stability at rated temperature and long hours of operation.
The LIS3DH accelerometer chip includes a temperature sensor and a three-way analog-to-digital converter for easy integration of companion chips such as gyroscopes. The LIS3DH also offers a variety of functions, including mouse click/double click recognition, 4D/6D direction detection, and power-saving sleep to wake-up mode. In sleep mode, the detection link remains active. When an event occurs, the sensor will wake up from sleep mode, automatically increasing the output data rate.
Other important features include a programmable FIFO (first in, first out) memory module and two programmable interrupt signal output pins that immediately notify the host processor of other conditions such as motion detection, click/double click events, and more.
As the latest MEMS product from STMicroelectronics, LIS3DH is designed and manufactured using ST's process technology for the sale of more than 700 million motion sensors.
2, Bosch
Smart bracelet representatives: ibody Rainbow, Jawbone UP, Smart Watch2, etc.
Sensor model: BMA250
Bosch Sensortec's BMA250 is a digital output low power triaxial accelerometer designed for the consumer electronics market. The BMA250 accelerometer's 2mm x 2mm small package and digital interface make it suitable for many consumer electronics manufacturers, especially in portable handhelds. On the device. The BMA250 accelerometer has four programmable measurement ranges from ±2g to ±16g, providing application developers with more development flexibility, higher measurement accuracy, and tens of data to provide maximum accuracy of less than 4mg.
3, ADI
Smart bracelet representative: Xiaomi bracelet
Sensor model: ADXL362
The ADXL362 is the industry's lowest power MEMS accelerometer from Analog Devices. The 3-axis digital MEMS accelerometer consumes only 300nA in motion-sensing wake-up mode, which consumes 60% less power in the same mode than the closest competing sensor.
In full-speed measurement mode, the power consumption is 2μA at 100Hz, which is 80% lower than competing MEMS accelerometers operating at the same frequency. In addition to the inherent low-power operating characteristics, the ADXL362 MEMS accelerometer has other system-level improvements. An important feature of efficacy.
The ADXL362 also features enhanced sample activity detection to accurately distinguish between different types of motion. This feature prevents false detections and prevents the sensor from unnecessarily turning the system on and reducing battery life.
The ADXL362 can be used as part of an intelligent, continuous operation, motion activated switch. When equipped with a wake-up status output pin, the motion sensor bypasses the processor to instantly trigger a switch that activates system functions, further reducing system power consumption. The extremely low power consumption makes the ADXL362 suitable for a wide range of battery life-critical applications from healthcare to infrastructure monitoring.
LIS3DH's software and pins are compatible with the STMicroelectronics LIS331 accelerometer family, allowing customers to directly change and easily upgrade to protect their investment in application development.
4. Asahi Kasei
Smart bracelet representative: LG Watch, Smart Watch2
Sensor model: AK8963
The AK8963 triaxial electronic compass chip is a highly sensitive Hall sensor technology. The small package of the AK8963 uses magnetic sensors to detect the X-axis, Y-axis and Z-axis, geomagnetic, sensor drive circuits, signal amplifier chains, and an arithmetic circuit that processes the signals from each sensor. Self-test features are also included. From its compact footprint and thin bag features, it is suitable for maps that go to GPS equipment to achieve the purpose of walking navigation for mobile phones or tablets.
The AK8963 has the following features:
· Silicon monolithic Hall effect magnetic sensor implements a three-axis magnetometer in a silicon chip. Analog circuits, digital logic circuits, power modules and interface modules are all integrated in one chip.
Wide dynamic measurement range and high resolution with low current consumption
· Resolution of output data: 14 bits (0.6μT / LSB) 16 bits (0.15μT / LSB
·Measurement range: 4900±μT
· Average current at repetition rate of 8 Hz: 280μ typical
5, InvenSence
Smart bracelet representative: LG Watch, Galaxy Gear, Gear Fit
Sensor model: MPU-6500
InvenSence's sensor MPU6500 integrates a 3-axis gyroscope and a 3-axis accelerometer. InvenSence uses a bulk silicon process with MEMS and ASIC chips integrated into a 3.0mm x 3.0mm x 0.9mm package.
The MPU6500's MEMS Sensor chip uses InvenSense's Nasiri process, which is tightly integrated with standard CMOS processes and uses bulk silicon technology to implement the main MEMS structure. The ASIC chip and the MEMS chip are constructed using a wafer-level aluminum crucible.
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