Wearable devices are moving towards medical grade, what new requirements are placed on components

From wristbands, smart watches to TWS earphones, there are always hot models in the wearable device market, so the market continues to heat up. At present, the annual shipment of wearable devices has surpassed that of personal computers, and it has become one of the application directions that component manufacturers must pay attention to. Among them, medical health has become the main function of wearable products. According to the statistics of market research organization Yole In 2019, the global shipments of wearable medical and health products reached 347 million pieces. The agency predicts that by 2025, the shipments of wearable medical and health products are expected to exceed 750 million pieces, doubling from 2019.

Wearable devices are moving towards medical grade, what new requirements are placed on components

From wristbands, smart watches to TWS earphones, there are always hot models in the wearable device market, so the market continues to heat up. At present, the annual shipment of wearable devices has surpassed that of personal computers, and it has become one of the application directions that component manufacturers must pay attention to. Among them, medical health has become the main function of wearable products. According to the statistics of market research organization Yole In 2019, the global shipments of wearable medical and health products reached 347 million pieces. The agency predicts that by 2025, the shipments of wearable medical and health products are expected to exceed 750 million pieces, doubling from 2019.

In 2022, the miniaturization and multi-functional integration of sensors and Chips will further increase the portability of wearable devices, or improve the continuous battery life of wearable devices; the interaction between smart wearable devices and other devices other than mobile phones such as smart home appliances The performance will be further strengthened; the control methods will be more diversified, and the gesture control function will be adopted by smart wearable devices; the independent communication function will gradually become the standard configuration of smart watches. In short, wearable devices will develop in the direction of richer functions, more diverse forms, more accurate indicators, and longer battery life, and play a greater role in many fields such as social networking, medical health, navigation, business and new media.

Wearable device data can be accepted by medical clinics

At present, sports health functions such as exercise recording and fitness guidance of wearable devices have been widely accepted. For example, common wristbands and watch products have the function of measuring indicators such as heart rate and cadence, but these data are usually not used in clinical practice. With the advancement of technology, more medical-grade monitoring functions are being added to wearable devices, such as the measurement of blood pressure, blood oxygen and electrocardiogram. The realization of these medical-grade functions marks the beginning of wearable devices for doctors’ clinical diagnosis and treatment. Reference data sources.

Since the outbreak of the new crown epidemic in 2019, there have been shortages of medical resources around the world, and the process of going to the hospital has become more cumbersome. Therefore, home medical monitoring equipment has become popular in the market. With wearable medical equipment, patients can monitor their own body temperature, Blood oxygen, heart rate and respiration, and can regularly transmit data to designated hospitals to complete functions such as predictive screening, disease detection, and home monitoring, providing patients with a time-saving, convenient and money-saving medical monitoring solution. The characteristic of smart wearable devices is that the more data that can be detected, the more value they can bring to users, so even if the normal life order is restored in the future, wearable medical devices will play an increasingly important role.

The portable nature of wearable devices is conducive to long-term monitoring of the physical condition of patients who do not need to be bedridden, which is of great help in the management of chronic diseases with certain fatal risks such as chronic obstructive pulmonary disease, atrial fibrillation, and obstructive sleep apnea.


Figure 1: Remote patient monitoring use case (Image source: ADI)

Atrial fibrillation screening (AFib) is a typical example of the medical application of wearable ECG devices. Atrial fibrillation (abbreviated as atrial fibrillation) is an extremely common persistent arrhythmia. During atrial fibrillation, the atrium beats irregularly at a rhythm much higher than the normal heartbeat. The atria loses coordinated and effective contraction and relaxation, which can easily lead to heart failure and cerebral infarction. It can even lead to sudden death, and once suffering from atrial fibrillation, the risk of stroke is five times higher than normal. However, if it can be detected and treated early, the effects of atrial fibrillation can be well controlled and even cured. However, the main difficulty in finding atrial fibrillation is that some patients do not have any symptoms when atrial fibrillation does not occur, and these patients account for about half of them. For asymptomatic people with atrial fibrillation, extensive screening is the only reliable method. Early atrial fibrillation screening can be done with consumer-grade ECG equipment, and the test results have also been recognized by medical clinics.

The blood oxygen test results of wearable devices are also gradually adopted in the clinical diagnosis and treatment of lung and respiratory diseases.2) is too low, often means heart failure, chronic lung disease, sleep apnea and other diseases, especially after the outbreak of the new crown epidemic, medical institutions also recommend monitoring the patient’s blood oxygen saturation to judge the severity of the disease.

In terms of diabetes management, patients can manage their own health more effectively through the data given by continuous glucose monitors, and based on the continuous measurement data, doctors can propose more accurate and effective treatment plans for patients.

Medical grade indicators and small size

To meet medical-grade applications, new requirements are put forward for key components in wearable devices: it is necessary to meet the “light, thin and short” size requirements of traditional wearable devices, and to meet the high-precision, high-reliability index requirements of medical-grade applications , but also considering low power consumption, endurance, and long-term work.

Medical-grade applications must first have medical-grade accuracy. Taking body temperature detection as an example, clinical-grade accuracy must reach an accuracy of ±0.1°C within the body temperature range. ADI’s MAX30208 digital temperature sensor can meet clinical body temperature detection requirements. The chip has an accuracy of ±0.1°C in the range of +30°C to +50°C, and an accuracy of ±0.15°C in the range of 0°C to +70°C. Since components will generate heat when they work, eliminating thermal interference of components is a factor that needs to be considered in clinical-grade temperature measurement equipment. The operating current of the MAX30208 itself is very low, only 67µA, and the current consumed in standby is 0.5µA. The low operating current ensures that the heat emitted by the chip itself is low. In addition, the chip heat is dissipated from the bottom pins of the package, so the chip places the temperature sensor on the top of the package, away from the chip pins, which greatly reduces the thermal interference of the components. Readers interested in this device can purchase the MAX30208 evaluation system on Mouser’s official website to experience it.


Figure 2: ADI MAX30208 evaluation system (Image source: Mouser Electronics)

The MAX30208 is a product of the third-generation Health Sensor Platform 3.0 (HSP 3.0) specially developed by Analog Devices for medical applications. HSP 3.0 also includes the MAX86176 analog front-end chip currently available on Mouser’s official website. The MAX86176 supports ECG and blood oxygen saturation measurements with clinical-grade accuracy.

When measuring an electrocardiogram (ECG) in a hospital, a wet electrode is usually used to collect the ECG signal. The wet electrode needs to be coated with a paste-like conductive glue during use, so it is named wet electrode. Because the conductive glue is easy to dry and affects the measurement results, so This method is not suitable for non-professionals to operate, and is not conducive to long-term monitoring of ECG signals. The emergence of dry electrodes makes it possible for wearable devices to achieve ECG measurement. However, in the dry electrode acquisition method, the contact conductivity between the skin and the electrode is lower than that of the wet electrode, and the dry electrode is more sensitive to motion artifacts, which is easy to cause The reading is inaccurate. The ECG channel of the MAX86176 meets the requirements of the international standard IEC 60601-2-47 for mobile ECG equipment. The channel has a built-in high-precision ADC and a fully differential input structure. The common-mode rejection ratio exceeds 110dB at the power line frequency. It is fully capable of supporting dry electrode ECG applications. ability. Now, the chip is widely used in single-lead monitors, single-lead wireless patches and chest strap heart rate monitors.

The MAX86176 uses photoplethysmography (PPG) to measure blood oxygen, providing a 110dB signal-to-noise ratio (SNR) for medical-grade oxygen saturation detection. For optical and bioimpedance measurements, LED drivers are required to emit light and to excite current into the body, respectively. In many optical systems, more than one wavelength needs to be used, so multi-drive capability is important. The MAX86176 supports up to 6 LEDs and 4 LEDs. Photodiode input, so it can adapt to the requirements of different measurement scenarios. The PPG channel of the MAX86176 can support the detection of heart rate, blood oxygen saturation (SpO2), muscle and tissue oxygen saturation (SmO2and StO2), body water content and other parameters, with clinical grade accuracy.


Figure 3: MAX86176 highlights (Image source: ADI)

Wearable devices have high requirements on the volume of components, so the MAX86176, an all-in-one high-integration chip, is very popular. The next-generation MAX86178 of the MAX86176 integrates three measurement systems, namely optics, ECG, and bioimpedance. Four vital sign measurements, namely electrocardiogram, blood oxygen saturation, heart rate and respiration rate, further provide a technical basis for the development of multifunctional wearable devices.


Figure 4: ADI MAX86176 PPG and ECG analog front end (Image source: Mouser Electronics)

The ADPD4000 sold on Mouser’s official website is another ADI wearable analog front-end “all-rounder” product series. This product has 8 input channels and has a variety of working modes. Impedance and temperature measurement functions.

It is understood that medical Electronic chip manufacturers represented by ADI are still making progress in improving integration, increasing functions and improving measurement accuracy, in order to bring more and better medical-grade functional experience to wearable users.

battery life

As mentioned above, portability is one of the outstanding advantages of wearable products, but it also brings many limitations to the development of wearable products. To be comfortable to wear, it is necessary to control the weight and volume, so the batteries of wearable devices are relatively small. In order to meet the normal use intensity requirements of medical and health applications under extremely limited battery capacity, it is necessary to make efforts to reduce power consumption and battery management.

In terms of low-power design, ADI’s HSP 3.0 platform has given a good demonstration role. Whether it is the MAX30208 digital temperature sensor or the MAX86176 analog front-end chip, the application scenarios are fully considered, and the working current and standby current are controlled as much as possible, just like the MAX30208. , the standby current of the MAX86176 is only 0.5μA.

The two ultra-low power consumption MCUs recommended by the platform fully consider the low power consumption characteristics of the device from the perspective of system design. The MAX32670 is dedicated to sensor management and supports pulse rate, blood oxygen saturation, heart rate, respiration rate, sleep quality monitoring, and stress monitoring algorithm implementation. The MAX32670 can be configured as a sensor concentrator (supports hardware and algorithms) or algorithmic concentrator (supports multiple algorithms), seamlessly supporting customer-required sensor functions, including managing the MAX86176 PPG and ECG sensor AFEs and providing raw data or external processed data. The MAX32670 consumes 2.6µA ​​for full memory retention in backup mode (from a 1.8V supply) and 350nA for RTC-only operation.

Another MCU-MAX32666 sold by Mouser Electronics is used for communication and main program. The chip supports Bluetooth Low Energy (BLE) function and includes two Arm®Cortex®– M4F core and additional SmartDMA, the latter allows to run the BLE stack independently, making the two main cores available to run the main task. In addition, the microcontroller integrates a complete security suite and memory error correction code (ECC), greatly improving system reliability. The MAX32666 provides dynamic voltage scaling, which greatly reduces the operating power consumption of the processor core. It supports executing programs from the cache, and the power consumption can be as low as 27.3μA/MHz @ 3.3V. In addition, the device features multiple shutdown modes to effectively extend battery operating life, consuming only 1.2μA @ 3.3V in the lowest power mode.

More importantly, in HSP 3.0, ADI also provides a dedicated power management chip MAX20360 for wearable devices, which is a highly integrated battery and power management chip, also available at Mouser Electronics. This chip is specially optimized for medical and health wearable applications. The chip integrates a high-precision ModelGauge™ m5 EZ fuel gauge, a sensitive haptic driver, and a unique low-noise step-up/step-down converter, which greatly improves signal-to-noise. ratio, reducing the power consumption required for optical biological detection.

Another single-input multiple-output power management MAX77659 sold by Mouser Electronics is optimized for multi-functional wearable products. The device requires only one Inductor to provide one charging voltage and three independently programmable supply voltages, thereby greatly reducing the overall solution size and reducing the bill of materials for power modules of multi-functional wearable devices by up to 60%. Equipment size can be reduced by 50%.

Summarize

The advancement of medical-grade wearable technology has improved the accuracy and reliability of the measurement results of wearable devices, and enabled wearable devices to integrate more functions while taking into account power consumption, size and weight considerations, thus ensuring wearable devices. The medical and health functions on wearable devices truly meet the requirements of clinical applications. Wearable devices are closer to the human body than any other device, so in addition to electrical parameters, wearable devices must also consider safety and ergonomics when developing them. various technical challenges, so as to be safe, waterproof and dustproof, comfortable to wear and durable.

It can be expected that with the popularization of medical functions of wearable devices, the value of wearable devices will be further exerted, and the wide application of medical functions can also better promote the development of related component technologies.

From wristbands, smart watches to TWS earphones, there are always hot models in the wearable device market, so the market continues to heat up. At present, the annual shipment of wearable devices has surpassed that of personal computers, and it has become one of the application directions that component manufacturers must pay attention to. Among them, medical health has become the main function of wearable products. According to the statistics of market research organization Yole In 2019, the global shipments of wearable medical and health products reached 347 million pieces. The agency predicts that by 2025, the shipments of wearable medical and health products are expected to exceed 750 million pieces, doubling from 2019.

From wristbands, smart watches to TWS earphones, there are always hot models in the wearable device market, so the market continues to heat up. At present, the annual shipment of wearable devices has surpassed that of personal computers, and it has become one of the application directions that component manufacturers must pay attention to. Among them, medical health has become the main function of wearable products. According to the statistics of market research organization Yole In 2019, the global shipments of wearable medical and health products reached 347 million pieces. The agency predicts that by 2025, the shipments of wearable medical and health products are expected to exceed 750 million pieces, doubling from 2019.

In 2022, the miniaturization and multi-functional integration of sensors and chips will further increase the portability of wearable devices, or improve the continuous battery life of wearable devices; the interaction between smart wearable devices and other devices other than mobile phones such as smart home appliances The performance will be further strengthened; the control methods will be more diversified, and the gesture control function will be adopted by smart wearable devices; the independent communication function will gradually become the standard configuration of smart watches. In short, wearable devices will develop in the direction of richer functions, more diverse forms, more accurate indicators, and longer battery life, and play a greater role in many fields such as social networking, medical health, navigation, business and new media.

Wearable device data can be accepted by medical clinics

At present, sports health functions such as exercise recording and fitness guidance of wearable devices have been widely accepted. For example, common wristbands and watch products have the function of measuring indicators such as heart rate and cadence, but these data are usually not used in clinical practice. With the advancement of technology, more medical-grade monitoring functions are being added to wearable devices, such as the measurement of blood pressure, blood oxygen and electrocardiogram. The realization of these medical-grade functions marks the beginning of wearable devices for doctors’ clinical diagnosis and treatment. Reference data sources.

Since the outbreak of the new crown epidemic in 2019, there have been shortages of medical resources around the world, and the process of going to the hospital has become more cumbersome. Therefore, home medical monitoring equipment has become popular in the market. With wearable medical equipment, patients can monitor their own body temperature, Blood oxygen, heart rate and respiration, and can regularly transmit data to designated hospitals to complete functions such as predictive screening, disease detection, and home monitoring, providing patients with a time-saving, convenient and money-saving medical monitoring solution. The characteristic of smart wearable devices is that the more data that can be detected, the more value they can bring to users, so even if the normal life order is restored in the future, wearable medical devices will play an increasingly important role.

The portable nature of wearable devices is conducive to long-term monitoring of the physical condition of patients who do not need to be bedridden, which is of great help in the management of chronic diseases with certain fatal risks such as chronic obstructive pulmonary disease, atrial fibrillation, and obstructive sleep apnea.


Figure 1: Remote patient monitoring use case (Image source: ADI)

Atrial fibrillation screening (AFib) is a typical example of the medical application of wearable ECG devices. Atrial fibrillation (abbreviated as atrial fibrillation) is an extremely common persistent arrhythmia. During atrial fibrillation, the atrium beats irregularly at a rhythm much higher than the normal heartbeat. The atria loses coordinated and effective contraction and relaxation, which can easily lead to heart failure and cerebral infarction. It can even lead to sudden death, and once suffering from atrial fibrillation, the risk of stroke is five times higher than normal. However, if it can be detected and treated early, the effects of atrial fibrillation can be well controlled and even cured. However, the main difficulty in finding atrial fibrillation is that some patients do not have any symptoms when atrial fibrillation does not occur, and these patients account for about half of them. For asymptomatic people with atrial fibrillation, extensive screening is the only reliable method. Early atrial fibrillation screening can be done with consumer-grade ECG equipment, and the test results have also been recognized by medical clinics.

The blood oxygen test results of wearable devices are also gradually adopted in the clinical diagnosis and treatment of lung and respiratory diseases.2) is too low, often means heart failure, chronic lung disease, sleep apnea and other diseases, especially after the outbreak of the new crown epidemic, medical institutions also recommend monitoring the patient’s blood oxygen saturation to judge the severity of the disease.

In terms of diabetes management, patients can manage their own health more effectively through the data given by continuous glucose monitors, and based on the continuous measurement data, doctors can propose more accurate and effective treatment plans for patients.

Medical grade indicators and small size

To meet medical-grade applications, new requirements are put forward for key components in wearable devices: it is necessary to meet the “light, thin and short” size requirements of traditional wearable devices, and to meet the high-precision, high-reliability index requirements of medical-grade applications , but also considering low power consumption, endurance, and long-term work.

Medical-grade applications must first have medical-grade accuracy. Taking body temperature detection as an example, clinical-grade accuracy must reach an accuracy of ±0.1°C within the body temperature range. ADI’s MAX30208 digital temperature sensor can meet clinical body temperature detection requirements. The chip has an accuracy of ±0.1°C in the range of +30°C to +50°C, and an accuracy of ±0.15°C in the range of 0°C to +70°C. Since components will generate heat when they work, eliminating thermal interference of components is a factor that needs to be considered in clinical-grade temperature measurement equipment. The operating current of the MAX30208 itself is very low, only 67µA, and the current consumed in standby is 0.5µA. The low operating current ensures that the heat emitted by the chip itself is low. In addition, the chip heat is dissipated from the bottom pins of the package, so the chip places the temperature sensor on the top of the package, away from the chip pins, which greatly reduces the thermal interference of the components. Readers interested in this device can purchase the MAX30208 evaluation system on Mouser’s official website to experience it.


Figure 2: ADI MAX30208 evaluation system (Image source: Mouser Electronics)

The MAX30208 is a product of the third-generation Health Sensor Platform 3.0 (HSP 3.0) specially developed by Analog Devices for medical applications. HSP 3.0 also includes the MAX86176 analog front-end chip currently available on Mouser’s official website. The MAX86176 supports ECG and blood oxygen saturation measurements with clinical-grade accuracy.

When measuring an electrocardiogram (ECG) in a hospital, a wet electrode is usually used to collect the ECG signal. The wet electrode needs to be coated with a paste-like conductive glue during use, so it is named wet electrode. Because the conductive glue is easy to dry and affects the measurement results, so This method is not suitable for non-professionals to operate, and is not conducive to long-term monitoring of ECG signals. The emergence of dry electrodes makes it possible for wearable devices to achieve ECG measurement. However, in the dry electrode acquisition method, the contact conductivity between the skin and the electrode is lower than that of the wet electrode, and the dry electrode is more sensitive to motion artifacts, which is easy to cause The reading is inaccurate. The ECG channel of the MAX86176 meets the requirements of the international standard IEC 60601-2-47 for mobile ECG equipment. The channel has a built-in high-precision ADC and a fully differential input structure. The common-mode rejection ratio exceeds 110dB at the power line frequency. It is fully capable of supporting dry electrode ECG applications. ability. Now, the chip is widely used in single-lead monitors, single-lead wireless patches and chest strap heart rate monitors.

The MAX86176 uses photoplethysmography (PPG) to measure blood oxygen, providing a 110dB signal-to-noise ratio (SNR) for medical-grade oxygen saturation detection. For optical and bioimpedance measurements, LED drivers are required to emit light and to excite current into the body, respectively. In many optical systems, more than one wavelength needs to be used, so multi-drive capability is important. The MAX86176 supports up to 6 LEDs and 4 LEDs. Photodiode input, so it can adapt to the requirements of different measurement scenarios. The PPG channel of the MAX86176 can support the detection of heart rate, blood oxygen saturation (SpO2), muscle and tissue oxygen saturation (SmO2and StO2), body water content and other parameters, with clinical grade accuracy.


Figure 3: MAX86176 highlights (Image source: ADI)

Wearable devices have high requirements on the volume of components, so the MAX86176, an all-in-one high-integration chip, is very popular. The next-generation MAX86178 of the MAX86176 integrates three measurement systems, namely optics, ECG, and bioimpedance. Four vital sign measurements, namely electrocardiogram, blood oxygen saturation, heart rate and respiration rate, further provide a technical basis for the development of multifunctional wearable devices.


Figure 4: ADI MAX86176 PPG and ECG analog front end (Image source: Mouser Electronics)

The ADPD4000 sold on Mouser’s official website is another ADI wearable analog front-end “all-rounder” product series. This product has 8 input channels and has a variety of working modes. Impedance and temperature measurement functions.

It is understood that medical Electronic chip manufacturers represented by ADI are still making progress in improving integration, increasing functions and improving measurement accuracy, in order to bring more and better medical-grade functional experience to wearable users.

battery life

As mentioned above, portability is one of the outstanding advantages of wearable products, but it also brings many limitations to the development of wearable products. To be comfortable to wear, it is necessary to control the weight and volume, so the batteries of wearable devices are relatively small. In order to meet the normal use intensity requirements of medical and health applications under extremely limited battery capacity, it is necessary to make efforts to reduce power consumption and battery management.

In terms of low-power design, ADI’s HSP 3.0 platform has given a good demonstration role. Whether it is the MAX30208 digital temperature sensor or the MAX86176 analog front-end chip, the application scenarios are fully considered, and the working current and standby current are controlled as much as possible, just like the MAX30208. , the standby current of the MAX86176 is only 0.5μA.

The two ultra-low power consumption MCUs recommended by the platform fully consider the low power consumption characteristics of the device from the perspective of system design. The MAX32670 is dedicated to sensor management and supports pulse rate, blood oxygen saturation, heart rate, respiration rate, sleep quality monitoring, and stress monitoring algorithm implementation. The MAX32670 can be configured as a sensor concentrator (supports hardware and algorithms) or algorithmic concentrator (supports multiple algorithms), seamlessly supporting customer-required sensor functions, including managing the MAX86176 PPG and ECG sensor AFEs and providing raw data or external processed data. The MAX32670 consumes 2.6µA ​​for full memory retention in backup mode (from a 1.8V supply) and 350nA for RTC-only operation.

Another MCU-MAX32666 sold by Mouser Electronics is used for communication and main program. The chip supports Bluetooth Low Energy (BLE) function and includes two Arm®Cortex®– M4F core and additional SmartDMA, the latter allows to run the BLE stack independently, making the two main cores available to run the main task. In addition, the microcontroller integrates a complete security suite and memory error correction code (ECC), greatly improving system reliability. The MAX32666 provides dynamic voltage scaling, which greatly reduces the operating power consumption of the processor core. It supports executing programs from the cache, and the power consumption can be as low as 27.3μA/MHz @ 3.3V. In addition, the device features multiple shutdown modes to effectively extend battery operating life, consuming only 1.2μA @ 3.3V in the lowest power mode.

More importantly, in HSP 3.0, ADI also provides a dedicated power management chip MAX20360 for wearable devices, which is a highly integrated battery and power management chip, also available at Mouser Electronics. This chip is specially optimized for medical and health wearable applications. The chip integrates a high-precision ModelGauge™ m5 EZ fuel gauge, a sensitive haptic driver, and a unique low-noise step-up/step-down converter, which greatly improves signal-to-noise. ratio, reducing the power consumption required for optical biological detection.

Another single-input multiple-output power management MAX77659 sold by Mouser Electronics is optimized for multi-functional wearable products. The device requires only one Inductor to provide one charging voltage and three independently programmable supply voltages, thereby greatly reducing the overall solution size and reducing the bill of materials for power modules of multi-functional wearable devices by up to 60%. Equipment size can be reduced by 50%.

Summarize

The advancement of medical-grade wearable technology has improved the accuracy and reliability of the measurement results of wearable devices, and enabled wearable devices to integrate more functions while taking into account power consumption, size and weight considerations, thus ensuring wearable devices. The medical and health functions on wearable devices truly meet the requirements of clinical applications. Wearable devices are closer to the human body than any other device, so in addition to electrical parameters, wearable devices must also consider safety and ergonomics when developing them. various technical challenges, so as to be safe, waterproof and dustproof, comfortable to wear and durable.

It can be expected that with the popularization of medical functions of wearable devices, the value of wearable devices will be further exerted, and the wide application of medical functions can also better promote the development of related component technologies.

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