“The growing use of portable medical devices (PMDs) over the past few years has been driven by a combination of factors, including technological advancements, pressure to reduce public health costs, and the desire to make hygiene solutions accessible to a wider patient population Driving the growth of the PMD market.

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The experience of fighting the new crown virus in the past three years has made people fully aware of the importance of their own health management, which has led to the application of portable medical devices in the home environment. Because it can be remotely monitored, non-invasive, and even wearable portable medical equipment, it can provide people with basic vital sign monitoring data at any time, effectively reducing people’s anxiety about their health and the number of visits to the hospital.

Taken together, the significant increase in the adoption rate of portable medical devices is mainly due to two factors. The first is the blessing of new technology, which has significantly improved its usability, accuracy and accessibility through the introduction of new technology in the device. Secondly, according to the “2022 World Population Prospects” report issued by the United Nations Department of Economic and Social Affairs, there will be 771 million people over the age of 65 in the world in 2022, and there will be 994 million elderly people in the world by 2030. 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 equipment is not only to test and monitor some physiological parameters, some equipment is now also endowed with recording and data analysis functions. For example, after the Electronic sphygmomanometer completes the measurement simply and quickly, it not only visually presents the current measurement results to the person being tested, but also stores the data for backup, so as to achieve the purpose of long-term tracking of blood pressure changes. Most of the current insulin meters are equipped with a communication port (IR/wireless), which can transmit real-time measured data to a PC or insulin pump, providing assistance for long-term treatment.

It can be seen that based on the consideration of 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 “complete internal organs”. Therefore, engineers do not feel comfortable designing such products, and there are a lot of design skills involved.

Portable Medical Equipment Market Analysis

The growing use of portable medical devices (PMDs) over the past few years has been driven by a combination of factors, including technological advancements, pressure to reduce public health costs, and the desire to make hygiene solutions accessible to a wider patient population Driving the growth of the PMD market.

According to Research And Markets, the global portable medical device market will reach $57.3 billion in revenue in 2022. The market will grow at a healthy CAGR of 9.2% during the forecast period 2022 to 2027. The total market capitalization of the portable medical devices market will reach USD 96.93 billion by 2027. By product type, products for diagnostic and monitoring purposes contribute nearly 44% to the market by 2027 and are expected to dominate the overall portable medical devices market. From 2022 to 2027, the portable medical device market in Asia Pacific will grow at a CAGR of 10.4%.

Figure 1: The global market for portable medical and healthcare devices is expected to reach $137.43 billion by 2030 (Source: Data Bridge Market Research)

According to an analysis by Data Bridge Market Research, the market for portable medical and healthcare devices is USD 64.58 billion in 2022 and is expected to reach USD 137.43 billion by 2030, at a CAGR 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 the growth of the market, and the use of these devices to remotely monitor the health status of patients is also effective in reducing healthcare costs.

Portable Medical Device Design Challenges and Solutions

The current challenge for portable medical devices is that it not only has remote connectivity capabilities, but also maintains the quality and responsiveness of all acquired data, and of course, portability is an important consideration. The reason why there is the term “portable” medical equipment is that compared with the large medical equipment used in hospitals, most of the hospital equipment is wheeled and it is 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 “dissect” a portable medical device, 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 interface (wireless and wired).

Figure 2: Block diagram of the main system of portable medical equipment (source: network)

Microcontroller (MCU)/DSP

Portable medical devices generate large amounts of raw data, and the ability to store and process data, identify changes, provide feedback, support interfacing with larger systems, and execute diagnostic algorithms are often important functions of the system microcontroller. However, ultra-low power consumption and high performance are often at odds with each other, and it is important to consider system processing requirements and power consumption constraints in a balanced manner during this process.

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 with low-power flash memory technology, programmable digital and analog resources, and first-class CAPSENSE Technologies for touch and proximity applications. With up to 2MB of flash memory, PSoC 62 enables medical/health care devices to implement multiple functions on a low-power platform, including sensor fusion for health diagnostics, graphics display and intuitive user interface. In terms of security, built-in hardware encryption accelerator, memory and peripheral protection unit. It is a low-power microcontroller designed for wearable devices, portable medical equipment, smart home and other applications.

Figure 3: PSoC 62 Family System Block Diagram (Source: Infineon)

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 applications. The RISC-V core handles timing-critical controller tasks, freeing programmers from worrying about Bluetooth interrupt latency. The Cryptographic 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 a secure bootloader. Internal code and SRAM space can be extended off-chip through two four-bit SPI execute-in-place (SPIXF and SPIXR) interfaces up to 512MB each.

Figure 4: Simplified block diagram of the MAX32690 microcontroller system (Source: Analog Devices)

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 FPGAs combine all the functionality required by designers of portable medical devices into a single chip, creating a truly programmable SoC solution with greater flexibility than traditional fixed-function microcontrollers.

At the heart of the SmartFusion device is an embedded ARM Cortex-M3 processor core. With its hardware multipliers and dividers, this 32-bit RISC processor offers high performance: about 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 running 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 sigma-delta DAC providing an effective 12-bit resolution at 500Ksps. In addition to MCUs, FPGAs, and configurable analog, SmartFusion FPGAs integrate extensive Flash and SRAM memory as well as comprehensive clock generation and management circuitry. The processor and its peripherals are interconnected by a multilayer High Performance Bus (AHB) Matrix (ABM). The ABM also provides a path for the processor and its peripherals to communicate with the FPGA fabric and embedded analog functions.

Figure 5: SmartFusion FPGA system block diagram (Source: Mouser)

Battery and Power Management

For portable medical devices, simple systems can use disposable batteries due to their very low power consumption, while larger systems require rechargeable cells and battery packs of various sizes. When it’s time to use the medical system, there’s not always time to wait to recharge. Dynamic power path management and other features can independently charge the battery while supplying power to the system without waiting for the battery to charge before operation. The lifetime of portable medical equipment can range from days, months, or even years, making power-optimized designs challenging.

The MAX14663 is a power-management solution for portable medical devices with cable detection that integrates a high-efficiency single-cell Li-Ion switching charger for space-constrained portable applications such as portable blood glucose meters. The MAX14663 embeds a patented ModelGauge that accurately estimates the usable capacity of a rechargeable Li-ion battery. Additionally, 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 choose their mode of operation, improving accuracy and reducing measurement errors. The MAX14663 also includes an ultralow-power sealed mode that significantly reduces standby current and preserves battery power during extended storage periods. This mode extends battery shelf life and improves the customer experience with immediate out-of-the-box use.

Figure 6: Functional block diagram of a typical application of the MAX14663 (Source: Analog Devices)

Data interface

Now, the data interface of portable medical electronic equipment has changed from wired RS232 interface to wired and wireless Ethernet connection, short-distance and long-distance wireless connection. 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 that measures 4 x 4 x 0.3 mm. BG22 is part of the wireless Gecko series platform, which has excellent ultra-low transmit and receive power and high performance. The BGM220S is an RF-certified Bluetooth Low Energy module with an antenna measuring 6 x 6 mm. The combination of superior RF technology and the low-power Arm Cortex-M33 core provides outstanding energy efficiency, extending coin cell battery life by up to ten years. Additionally, compact modules and SoCs allow the flexibility to design smaller, more attractive devices, leaving more room for memory and batteries. Target applications for this SoC include Bluetooth mesh low-power nodes, portable healthcare and fitness devices, smart door locks, and more.

Figure 7: EFR32BG22 system block diagram (Source: Silicon Labs)

display technology

As a design engineer, display selection is a high priority, and display modules often represent the first, second, or third most expensive item on the BOM. Display selection in portable medical devices must also follow low power sleep modes, most display drivers will have an ultra low power mode and be able to reduce brightness by using PWM backlight control, or in the case of OLED technology, simply use correct command or register setting.

Touch Screen Control (TSC) is a key factor in the convenience of portable medical devices, replacing the traditional keyboard and greatly reducing the overall size of the device. TSC realizes menu-driven function selection, fine-tuning and zoom-in of input and output data display, which significantly enhances the usability of the device. The electrostatic (ESD) handling capability of the selected solution is an important factor to consider when implementing TSC.

Sensor interface and signal chain technology

The correct signal chain is very important for temperature, pulse, blood glucose readings and other biosensors. In most applications, designers try to find microvolt-level signals in millivolt noise. Due to the AC nature of the signal of interest, an amplifier that works well with the high-pass filtering scheme, and an analog-to-digital converter with good performance are required. Now, some highly integrated MCU products on the market have already absorbed these functions into the products to form a powerful SoC solution, such as the SmartFusion FPGA of Microchip Company introduced earlier.

epilogue

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 diseases, 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 by bringing care from the hospital or doctor’s office to the user’s home, providing added convenience to patients.

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