“Nowadays, smart wearable products have become an indispensable part of our daily life. Products such as earphones, smart watches, bracelets, and smart glasses have become a must for modern people. In September 2014, Apple launched its first smartwatch. Since then, Apple has lifted the curtain of smart wear in the market, and many companies such as Amazon, Samsung, Huawei, OPPO, vivo, etc. have all been involved in the wave caused by smart wear.

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Author: Frank Cai

Nowadays, smart wearable products have become an indispensable part of our daily life. Products such as earphones, smart watches, bracelets, and smart glasses have become a must for modern people. In September 2014, Apple launched its first smartwatch. Since then, Apple has lifted the curtain of smart wear in the market, and many companies such as Amazon, Samsung, Huawei, OPPO, vivo, etc. have all been involved in the wave caused by smart wear.

From IDC’s research reports on smart wearable shipments in 2015, 2016, 2019 and 2020, it can be seen that the shipments of smart wearable devices are increasing year by year. Several major manufacturers in 2015 and 2016 include: Xiaomi (37.4% market share), Little Talent (7.4% market share), Lexin and Huawei (5.4% and 5.1%) and Apple (3.4%). In 2020, the main manufacturers of the smart wearable market have undergone a big change. From the above-mentioned manufacturers, it has become a major manufacturer of mobile phone manufacturers, such as Huawei, Xiaomi, OPPO, Apple and BBK. At the same time, in terms of share, it is no longer the dominant situation of Xiaomi. After various mobile phone manufacturers joined the smart wearable market, the situation has become a multi-polar trend. Every mobile phone manufacturer regards smart wear as an important part of the ecological environment of its own products. Take Huawei’s wearable devices as an example. In the fourth quarter of 2015, Huawei’s shipments were only 639,000 units. In the same quarter of 2019, its shipments soared to 6,182 thousand units. By 2020, shipments of wearable devices will still grow slightly, reaching 6,761,000 units. It can be seen that the smart wearable market still has great development potential, and more and more different companies have joined this market to compete for share.

The most important point in developing different new products is how to catch the eyes of customers, and the products need to be able to meet their needs. With the development of science and technology, health has always been a topic of concern to everyone. How to check their own health status in a timely manner will be a focus for customers in the future, and it is also one of the selling points that products need to have. Instead of going to the hospital for regular physical examinations, customers want to know their own situation in a simple way. Therefore, if it is a smartwatch that can integrate sleep monitoring, motion detection, and even support biosignal detection, such as electrocardiogram (ECG), photoplethysmography (PPG), bioimpedance (BIO-Z) measurement, etc. So can this product attract customers to buy it? The answer is yes. Therefore, integrating different health detection functions has gradually become the mainstream trend of smart wearable products. Because this type of smart wearable product or portable health monitor is completely unlike traditional medical equipment (especially in terms of product size and measurement accuracy). Therefore, we call it “new health monitoring products”.

The human body has many types of physiological signals, such as the PPG and ECG just mentioned, what do they represent? ECG, also known as electrocardiogram, can diagnose various heart diseases and abnormal states by measuring electrical signals in the body. In contrast, PPG uses the light transmitter of new health products to generate specific wavelengths of absorbed light that penetrates the skin and blood of the human body, and is reflected to the receiver, where the light signal is converted into an electrical signal by conversion in the product. Information about blood pressure and blood flow in the human body. Finally, customers can see relevant data through portable monitoring products such as smart watches and wristbands.

Figure 3: Simplified PPG detection process

It can be seen that in order to meet the multi-application and multi-channel requirements of new health monitoring products, AFE products need to be able to support multi-application scenarios and multi-channel requirements. In addition, since physiological signals are relatively weak in the body and are easily interfered by the outside world, AFE also needs to be able to detect weak signals, amplify signals, and have appropriate anti-interference capabilities. Taking ECG measurement as an example, people use the differential voltage between two electrodes connected to the human body, or the differential voltage between multiple electrodes (for different lead requirements), and take the average value to reflect the state of the heart. Because electrical signals in the human body are very weak and difficult to detect, high-precision amplifiers are essential to measure these electrical signals. TI can address these applications by using different AFE products and setting up total system solutions. In the detection of ECG, we can use the ADS129x series (here, the ADS1292R is used as an example).

The ADS1292R fully integrates ECG detection and respiratory impedance measurement (RESP) for portable, low-power physiological signal measurement products. There are two low-noise PGAs and two high-resolution ADCs inside the device, which are used for the detection, measurement and amplification of weak electrical signals. At the same time, the gain of the PGA is optional, which can meet different application scenarios. The ADS1292R is very competitive in the AFE market due to its high level of device integration, which integrates functions such as the right leg drive circuit (RLD) and lead-off detection. For customer-specific applications, such as using multiple channels for both ECG and RESP detection and measurement, this can be easily implemented by paralleling two ADS1292Rs. More detailed parameters and usage methods can be found in the data sheet of ADS1292R.

TI provides AFEs with various channels and functional options for different customers, which can meet the application scenarios of different needs, and provide flexible solutions to achieve corresponding functions. In addition to diversified functions and channels, TI’s AFE also has certain advantages in terms of power consumption, noise performance, package size, etc. These characteristics need to be fully considered in the customer’s design. TI’s products can make the design more flexible and convenient, and can help Customers simplify PCB layout and reduce costs.

In addition to the ADS129x series, TI has many highly integrated products that can support various application scenarios. For example, the product AFE4500 can support the above functions as well as bioimpedance analysis and optical biosensing. By measuring bioimpedance, through algorithm calculation and derivation, the composition and physiological data of different substances in the human body can be obtained, such as body fat, moisture, etc. Some terminal products on the market have also realized how to quickly and conveniently obtain the physiological data of the human body. In addition, due to the integration of ECG, PPG and other functions, the use of AFE4500 in portable or smart wearable devices can simultaneously obtain different physiological data. The design not only simplifies the mutual interference of complex circuits and separation schemes, but also brings customers Highlights of the product. For consumers, an end product that can integrate multiple functional measurements must be a differentiated product. There are a wide variety of TI-based AFE products, and the following is a simplified selection table that can be used as a reference for your selection. For more AFE devices, you can check the reference link to learn more about TI’s AFE products.