Integrating Smart Technology in Portable Medical Devices

The rapid development of medical technology, particularly the rise of the Internet of Medical Things (IoMT), is transforming healthcare delivery.

Image Credit: Andrey_Popov/Shutterstock

Modern connected medical devices are playing a crucial role in monitoring patients’ health in real-time, automating medical tasks, and improving access to care. Devices like wearables and mobile health monitors are now not just integral but indispensable to preventive healthcare, empowering users to track everything from heart rates to blood oxygen levels and thereby taking control of their health.

By 2025, the IoMT market is projected to soar to $250 billion, a staggering figure that underscores the rapid growth and immense potential of this industry. This growth, driven by a compound annual growth rate of nearly 20 %, presents a vast opportunity for innovation in mobile and wearable healthcare devices. However, with this opportunity comes the challenge of ensuring device reliability and safety, given their continuous operation and exposure to various hazards.

Figure 1. Connected healthcare – portable medical devices and the Internet of Medical Things (IoMT). Image Credit: Littelfuse

Key Design Challenges for Medical Devices

Wearable medical devices must deliver consistent and reliable performance. They operate around the clock, often without the ability for frequent intervention or maintenance. From ensuring battery longevity to maintaining functionality in adverse conditions, engineers face significant obstacles in designing these compact yet highly capable devices. Additionally, they must protect against electrical threats such as overcurrent, electrostatic discharge (ESD), and temperature spikes.

Protecting Wearable Health Devices

Wearable health devices, such as fitness trackers and smart health monitors, have become indispensable in both consumer wellness and clinical care. These devices provide data that medical professionals can use for diagnostics and treatment. To enhance durability and functionality, it is essential to protect critical components, such as the battery pack, display, user interface, and charging circuitry.

Figure 2. Smart health monitor wearable and block diagram. Image Credit: Littelfuse

Wireless Charging Circuits

A key feature of most wearable devices is wireless charging, typically achieved through a USB-C connection. This method delivers power up to 20 VDC and 5 VAC, which can put significant stress on the device’s circuitry if not properly protected. Overcurrent failures are common, and adding fuses or polymer positive temperature coefficient (PPTC) resettable fuses can help mitigate these risks.

Electrostatic discharge (ESD) is another potential threat to the wireless charging circuit. To shield the device from high-voltage surges, transient voltage suppressor (TVS) diodes can be deployed. These diodes are capable of clamping dangerous voltage spikes, dissipating the energy to protect the device.

For more comprehensive protection, an eFuse Protection IC integrates multiple functions into a single, compact solution. This device combines overcurrent, overvoltage, and overtemperature protection while saving PCB space. Additionally, it offers under-voltage lockout (UVLO) and inrush current limiting features that improve overall safety.

Figure 3. Overcurrent, overvoltage protection schematic (eFuse Protection IC example from Littelfuse), Image Credit: Littelfuse

USB Type-C Port Protection

USB Type-C connectors are now the standard for portable devices, but their dense pin layout makes them vulnerable to shorts, particularly from dust and debris. The setP^™ digital temperature indicator provides an effective solution, monitoring temperature levels and cutting power to prevent connector damage if temperatures rise too high.

The setP can trigger at 100 °C, signaling the communication channel to halt power delivery, effectively preventing overheating without interrupting the power flow under normal conditions. This component is USB-IF compliant and designed for minimal impact on power efficiency.

Figure 4. Resistance vs. Temperature curve (example of Littelfuse setP Digital Temperature Indicator). Image Credit: Littelfuse

Battery Pack Safety

For battery pack safety, fast-acting PPTC resettable fuses are the ideal choice. These fuses react swiftly to overcurrent conditions, transitioning to a high-resistance state in milliseconds, thereby cutting off the power flow before any damage occurs. Their fast response time and small surface-mount packages, as small as 1.5 x 0.8 mm, make them suitable for the compact designs of wearable devices, ensuring both safety and space efficiency.

Display and ESD Protection

The touchscreen, serving as the primary interface for many wearable health devices, is vulnerable to ESD, particularly from user contact. To protect against these discharges and maintain the device’s functionality, TVS diodes are the solution. These diodes absorb the energy from ESD events, ensuring minimal impact on the device’s performance. Some TVS diodes are designed specifically for low-power applications, with leakage currents below 0.5 µA, ensuring minimal battery drain and a seamless user experience.

Ensuring Long-Lasting User Interface Controls

User interface buttons are essential for controlling device functions. These buttons must withstand daily use and exposure to environmental factors such as moisture and dust. Designers can achieve this by incorporating switches with IP67-rated environmental protection, ensuring resistance to water and dust. Surface-mount switches are available in sizes as small as 2.1 x 1.65 mm, and with operational lifespans of over 300,000 cycles, they provide both durability and reliability.

Hearing Aid Protection

Hearing aids, another key IoMT device, require the same level of protection as wearables but with even more emphasis on durability due to their small size and continuous use. The volume controls and buttons need switches that can resist moisture and debris while still being compact enough for the limited space available. USB charging ports, especially in devices like health monitors, must be protected from ESD. One effective way to achieve this is by using TVS diodes.

Figure 5. Hearing aid and block diagram. Image Credit: Littelfuse

Overcurrent and Overvoltage Protection

Hearing aids often use USB Type-C ports for charging, and these circuits must be protected from electrical hazards. The eFuse family, also applicable in health monitors, can be used to prevent overcurrent, overvoltage, and overtemperature conditions. Smaller eFuse packages, like those measuring just 1.2 x 1.6 mm, reduce the device footprint while providing reliable protection.

For simpler overcurrent protection, PPTC fuses are an efficient choice, consuming minimal power and requiring little PCB space. PPTC fuses in 0402 packages provide overcurrent protection with resistance values in the milliohm range, preserving battery life while offering robust safety.

Overcoming Design Challenges with Advanced Protection Components

Wearable medical devices will only fulfill their potential if they function reliably under various conditions. By incorporating a few additional components, designers can greatly enhance the robustness and safety of these devices.

Solutions like eFuse Protection ICs and set Digital Temperature Indicators not only ensure protection against electrical hazards but also help save space and reduce power consumption. Designers can also simplify development by working closely with component manufacturers who offer expertise in component selection and certification standards.

These partnerships are not just beneficial but crucial, helping streamline the design process and ensuring that the final product meets all necessary regulatory requirements while staying compact and cost-effective.

Conclusion

As smart technology continues to transform healthcare, the demand for reliable, connected medical devices will only grow. Engineers must address the unique challenges of protecting these devices from electrical hazards while maintaining functionality, efficiency, and compactness.

By leveraging advanced protection components and collaborating with manufacturers, designers can build wearable medical devices that are both innovative and dependable, ensuring better outcomes for patients and healthcare providers alike.

Download Littelfuse Inc.’s presentation to explore how Littelfuse solutions help meet the FDA, IEC, and ISO test standards of this emerging market.

About the Author

Dr. Marco Doms is the Sr. Manager of Business Development New Platforms at Littelfuse, Inc.

Marco studied electrical engineering and holds a Ph.D. in MEMS. He was the head of R&D in two other sensor companies before joining Littelfuse in 2022. Marco has a long history in position sensors (especially xMR) and managing R&D and Innovation teams—from chip to system level.

At Littelfuse, he started as an Innovation Manager, led the EBU Advanced Development team, and introduced an Innovation/Idea Management process. In his current role, Marco is responsible for several platforms with entirely new products or product features that require additional internal and customer coordination.

This information has been sourced, reviewed and adapted from materials provided by Littelfuse.

For more information on this source, please visit Littelfuse.