"Dissect" portable medical devices to see what's inside?

Taken together, the sharp increase in the adoption rate of portable medical devices is mainly due to two major factors. The first is the blessing of new technologies. The new technologies introduced into the device significantly improve its practicality, accuracy and accessibility. Secondly, according to the "World Population Prospects 2022" report released by the United Nations Department of Economic and Social Affairs, 771 million people will be 65 or older in the world in 2022, and there will be 994 million elderly people in the world by 2030. By 2050, this number will Will reach 1.6 billion. With the rapid growth of the global elderly population, the demand for health status monitoring has become another important factor driving the growth of the portable medical device market.

In practical applications, the role of portable medical devices is not only to test and monitor some physiological parameters, but some devices are now also equipped with recording and data analysis functions. For example, after the electronic blood pressure monitor completes the measurement simply and quickly, it not only visually presents the current measurement results to the person being measured, but also stores these data for backup to achieve the purpose of long-term tracking of blood pressure changes. Most of today's insulin meters are equipped with communication ports (IR/wireless), which can transmit real-time measurement data to a PC or insulin pump to provide assistance in implementing long-term treatment.

It can be seen that based on application scenarios, most portable medical devices are battery-powered, small-sized, and easy-to-operate handheld devices. No matter how small a portable medical device is, it is also a sophisticated electronic product with "all the internal organs". Therefore, engineers do not feel relaxed when designing such products. There are many design skills involved.

Portable Medical Device Market Analysis

Over the past few years, the use of portable medical devices (PMDs) has become increasingly widespread, with a combination of factors including technological advances, pressure to reduce public health costs, and the desire to make health solutions accessible to a wider patient population. Driving the growth of the PMD market.

Research And Markets found that the global portable medical device market revenue will reach $57.3 billion in 2022. The market will grow at a healthy CAGR of 9.2% during the forecast period from 2022 to 2027. By 2027, the total market value of the portable medical device market will reach US$96.93 billion. By product type, products used for diagnostic and monitoring purposes will contribute nearly 44% to the market by 2027 and are expected to dominate the entire portable medical devices market. From 2022 to 2027, the compound annual growth rate of the portable medical device market in the Asia-Pacific region will reach 10.4%.

Analysis by Data Bridge Market Research shows that the portable medical and healthcare device market is US$64.58 billion in 2022 and is expected to reach US$137.43 billion by 2030, with a compound annual growth rate of 9.9% between 2023 and 2030. Among them, the increasing popularity of wearable devices and other portable technologies is one of the key factors driving market growth. Using these devices to remotely monitor patients' health conditions can also effectively reduce medical costs.

Portable Medical Device Design Challenges and Solutions

The current challenge for portable medical equipment is that it not only needs to have remote connectivity capabilities, but also needs to maintain the quality and responsiveness of all collected data. Of course, portability must also be an important consideration. The reason why there is a term "portable" medical equipment is mainly because compared with the large medical equipment used in hospitals, most of the hospital equipment is wheeled and difficult to move. Today’s “portable” medical devices are not only easy to transport, but many are even “wearable”. These changes have brought many challenges to designers' design work.

If we do an "anatomy" of a portable medical device, we will find that there are several functional blocks that are common to most portable home and consumer medical devices, namely: biosensors, amplification and analog-to-digital conversion of sensor inputs, battery and power management , low-power microcontroller or digital signal processor (DSP), user interface or display, human machine interface (HMI), and data interfaces (wireless and wired).

Microcontroller (MCU)/DSP

Portable medical devices generate large amounts of raw data, and the ability to save and process data, identify changes, provide feedback, support connections to larger systems, and execute diagnostic algorithms are often important functions of the system's microcontroller. However, ultra-low power consumption and high performance are often contradictory, and in this process, it is very important to consider system processing requirements and power consumption constraints in a balanced manner.

For example, the Infineon PSoC 62 series is a combination of Arm Cortex-M4 and Arm Cortex-M0+CPU. This product is based on an ultra-low-power 40nm platform and features low-power flash memory technology, programmable digital and analog resources, and first-class CAPSENSE Technology for touch and proximity applications. PSoC 62 features up to 2MB of flash memory, enabling medical/healthcare devices to implement multiple functions on a low-power platform, including sensor fusion for health diagnostics, graphical displays, and intuitive user interfaces. In terms of security, there are built-in hardware encryption accelerators, memory and peripheral protection units. It is a low-power microcontroller designed for wearable devices, portable medical devices, smart homes and other applications.

Architecturally, Analog Devices' MAX32690 microcontroller is a system-on-chip (SoC) with FPU microcontroller and BLE 5, featuring an Arm Cortex-M4F CPU, large flash and SRAM memory, and next-generation Bluetooth 5.2. The device combines processing power with the connectivity required for wearable device applications. The RISC-V core handles timing-critical controller tasks so programmers don't have to worry about Bluetooth interrupt latency. The Cryptozoological Toolbox (CTB) provides advanced security features including MAA for fast Elliptic Curve Digital Signature Algorithm (ECDSA), Advanced Encryption Standard (AES) engine, TRNG, SHA-256 hashing and secure bootloader. Internal code and SRAM space can be extended off-chip via two four-bit SPI in-place execution (SPIXF and SPIXR) interfaces, up to 512MB each.

A key design consideration for portable medical devices is low power consumption, driven by the need to extend battery life. Other requirements include faster time to market, low cost, reliability, small size and higher integration. Microchip's SmartFusion FPGA combines all the functionality portable medical device designers need into a single chip, creating a truly programmable SoC solution with greater flexibility than traditional fixed-function microcontrollers.

At the heart of SmartFusion devices is an embedded ARM Cortex-M3 processor core. Through its hardware multipliers and dividers, this 32-bit RISC processor offers high performance: approximately 125 Dhrystone MIPS. Portable medical designs must interface directly with various biosensors, and the programmable analog section or analog front end (AFE) of the SmartFusion FPGA contains the required components such as analog-to-digital converters (ADCs) and digital-to-analog converters (DACs).

Each SmartFusion FPGA contains up to three 12-bit successive approximation register (SAR) ADCs capable of operating at 500ksps in 12-bit mode (550ksps in 10-bit mode, 600ksps in 8-bit mode). To process signals in the other direction, each device is equipped with a first-order Σ-ΔDAC, providing effective 12-bit resolution at 500Ksps. In addition to the MCU, FPGA and configurable analog, SmartFusion FPGA integrates extensive flash and SRAM memory and comprehensive clock generation and management circuitry. The processor and its peripherals are interconnected through a multilayer high-performance bus (AHB) matrix (ABM). ABM also provides a path for the processor and its peripherals to communicate with the FPGA fabric and embedded analog functions.

Battery and power management

For portable medical devices, simple systems can use disposable batteries due to very low power consumption, while larger systems require the use of rechargeable cells and battery packs of various sizes. When it's time to use a medical system, there's not always time to wait for a recharge. Dynamic power path management and other features can charge the battery independently while delivering power to the system, eliminating the need to wait for the battery to charge before running. The service life of portable medical devices can vary from days, months, or even years, making power supply optimization design challenging.

The MAX14663 is a portable medical device power management solution with cable detection that integrates a high-efficiency single-cell Li-ion switching charger for portable applications with limited space (such as portable blood glucose meters). The MAX14663 embeds a patented ModelGauge that accurately estimates the available capacity of rechargeable lithium-ion batteries. In addition, a boost converter and LED current sink are integrated for powering OLED displays or LED backlights. Internal cable detection circuitry enables the MAX14663 to recognize the presence of an unpowered/unconnected USB cable. Portable systems can use this information to intelligently select their operating modes, thereby improving accuracy and reducing measurement errors. The MAX14663 also includes an ultra-low-power sealed mode that significantly reduces standby current and preserves battery charge during extended storage periods. This mode extends battery shelf life and improves the customer experience by enabling immediate use out of the box.

Data interface

Now, the data interface of portable medical electronic equipment has changed from wired RS232 interface to wired and wireless Ethernet connections, short-distance and long-distance wireless connections. The new interface enables networking of all devices in the building, including those in the patient's home.

Silicon Labs offers several compact wireless solutions for portable medical devices, such as the EFR32BG22 Bluetooth Low Energy (BLE) SoC measuring 4x4 x 0.3 mm. BG22 is part of the wireless Gecko series platform and features excellent ultra-low transmission and reception power and high performance. The BGM220S is an RF-certified low-power Bluetooth module with an antenna and a size of 6 x 6 mm. The combination of superior RF technology and the low-power Arm Cortex-M33 core delivers outstanding energy efficiency, extending coin cell battery life to up to ten years. In addition, compact modules and SoCs allow the flexibility to design smaller, more attractive devices, leaving more space for memory and battery. Target applications for the SoC include Bluetooth mesh network low-power nodes, portable healthcare and fitness devices, smart door locks, and more.

display technology

As a design engineer, display selection is a high priority, with display modules often representing the first, second or third expensive item on the BOM. Display selection in portable medical devices must also respect low power sleep modes, most display drivers will have ultra-low power modes and the ability to reduce brightness by using PWM backlight control, or in the case of OLED technology, simply using the correct commands or register settings.

Touchscreen control (TSC) is a key factor in enabling the convenience of portable medical devices, replacing traditional keyboards and significantly reducing the overall size of the device. TSC realizes menu-driven function selection, fine-tuning and amplification of input and output data display, significantly enhancing the ease of use of the device. The electrostatic discharge (ESD) handling capability of the chosen solution is an important factor to consider when implementing TSC.

Sensor interface and signal chain technology

The correct signal chain is important for temperature, pulse, blood glucose readings and other biosensors. In most applications, designers try to find microvolt-level signals among millivolt noise. Due to the AC characteristics of the target signal, an amplifier that works well with a high-pass filtering scheme is required, as well as an analog-to-digital converter with excellent performance. Now, some of the more highly integrated MCU products on the market have already absorbed these functions into their products, forming powerful SoC solutions, such as Microchip's SmartFusion FPGA introduced earlier.

Conclusion

Portable medical devices are characterized by their low power consumption, reliability and cost-effective sensor technology. They help in the early detection of various diseases, including diabetes and cardiovascular disease, and the use of these portable devices reduces the number of doctor visits for users. The use of portable medical devices in the healthcare industry can simplify and improve patient care. They bring care from the hospital or doctor's office to the user's home, providing patients with more convenience.

Today, portable medical devices play a vital role in monitoring and managing medical conditions worldwide. More and more devices are powered by new technologies, such as integrating new wireless communication technologies, resulting in more intelligent, intuitive, networked devices and even wearable devices. These devices are widely involved in monitoring and tracking people's health, and some have even become auxiliary diagnostic tools. Based on these changes, the system design of portable medical equipment must also keep up with market trends and fully consider power consumption, system performance, connectivity, cost and size. Designers have a long way to go.