Tips and solutions for designing small Bluetooth health devices and wearables

When a smart tooth implant can adhere to the tooth surface and capture over a thousand health indicators from saliva, the miniaturization of wireless healthcare devices is no longer just a technological vision - it is a reality unfolding before us. From continuous glucose monitors to wearable patches, the Internet of Medical Things (IoMT) is packaging powerful computing capabilities and Bluetooth connectivity into increasingly tiny volumes. This article will walk you through key techniques for designing small Bluetooth healthcare devices and share how Silicon Labs' highly integrated SoCs can help innovators push the boundaries of miniaturization, bringing connected health to applications never before imagined.

As modern people place greater emphasis on their health status and technology advances rapidly, the Internet of Medical Things is experiencing accelerated growth. Today, technological innovation in this field is flourishing, and the adoption rate of connected healthcare devices is accelerating continuously. Unit shipments of wireless medical devices are predicted to grow by 40% compared to 2024 levels, from 329 million units shipped in 2024 to 544 million units predicted in 2028.
 
The drivers behind IoMT growth are multifaceted. Wireless computing platforms are becoming smaller, smarter, and more powerful. Microprocessor clock speeds and memory capacities are increasing. Hardware AI/ML accelerators have been integrated into wireless microcontrollers, and security continues to strengthen. Yet, the size of microprocessors remains the same or even shrinks.
 
The continuous miniaturization of wireless computing is a key driver for the evolution of the Internet of Medical Things. Lura Health, an innovative health technology company, introduced the world's smallest connected wearable device in 2023, a smart tooth implant. This miniature device is glued to a tooth and features powerful computing and high-performance Bluetooth LE connectivity, allowing dentists and clinicians to collect important data from saliva. Saliva is an important health indicator used to test more than 1,000 health conditions.
 
These trailblazing device makers are constantly pushing the limits of tiny connectivity, integrating wireless functionality into ever smaller device form factors and into applications that nobody ever imagined would be connected. Building Bluetooth medical devices with small and challenging form factors is not only about picking the smallest hardware components from the market - you can also reduce the size of your product by optimizing the bill of materials (BoM).

When designing wireless healthcare products, there are several important Bluetooth design concepts that can help you save PCB footprint, reduce design costs, and optimize the BoM in healthcare applications. The first is adopting an advanced integrated AI/ML accelerator. Machine Learning (ML) allows large volumes of sensor data to be processed against existing models to identify irregularities and determine which data needs to be transmitted back to the cloud. For example, devices such as EKGs transmit all collected data back to the cloud for processing and analysis. By identifying key data on the device, only certain subsets of data need to be transmitted back, saving precious resources and extending battery life.
 
Artificial Intelligence (AI) can also be utilized in applications such as aging in place, where monitoring vitals, analyzing changes in data, observing gait, and identifying patterns outside the norm can provide crucial diagnostic data to healthcare providers and trigger life-saving alerts to caretakers and loved ones, dramatically improving or even saving a patient's life.
 
Analog peripherals are an important component of wireless healthcare devices. ADCs are widely used on wireless healthcare devices and wearables to enable sensor measurement and battery supply monitoring. Additionally, for CGM manufacturers (and other portable healthcare devices) using a discrete Analog Front End (AFE), the ADC and DAC are two critical functions that can be integrated on-chip, eliminating the need for additional components on the board.
 
A DC-DC converter is a valuable function for battery-powered healthcare devices. A Boost Converter allows an SoC to operate with lower-voltage batteries like alkaline and silver oxide with an input range of 0.8 to 1.7 V, enabling a Bluetooth SoC to operate from lower supply voltages. The Buck Converter allows an SoC to operate with other ~3V batteries, such as lithium coin cells, and is used to improve energy efficiency and battery life or to reduce the size of a battery. Furthermore, to predict and prevent unexpected battery depletion during the use of critical health applications, a Coulomb Counter enables accurate battery level tracking to enhance user safety and experience.
 
A Low-Frequency RC Oscillator (LFRCO) is an important component for adjusting clock accuracy. For Bluetooth LE 2.4 GHz applications, the Bluetooth LE SoC needs to meet the specified Sleep Clock accuracy of ±500 ppm. On the other hand, a matching network is an essential function for wireless healthcare devices. However, healthcare devices and wearables use lower power levels, which means you can reduce the number of PCB layers and components while maintaining acceptable RF performance. Additionally, minimizing the power consumption of a Bluetooth device enables device makers to achieve smaller device form factors.

To meet the design requirements of wireless healthcare devices, you can use Silicon Labs' integrated Bluetooth SoCs and modules, which include various peripheral functions and features needed in medical applications, saving significant PCB footprint, enhancing design flexibility, and reducing costs. Silicon Labs has been working with many healthcare device makers for decades. As a result of these successful engagements, Silicon Labs has developed several functionalities relevant to wireless healthcare applications and integrated them into its Bluetooth SoCs and modules. Silicon Labs' Bluetooth solutions feature robust security with up to the highest PSA Level 3 Certification and DTSec, the Cybersecurity Standard for Connected Diabetes Devices.
 
To deliver more powerful computing and security capabilities for small healthcare devices, Silicon Labs has launched the new BG29 Bluetooth LE SoC, bringing high compute, large memory, and high-performance Bluetooth (LE) connectivity to the smallest form factor devices. The BG29 is designed for advanced connected medical and health applications, such as wearables, patches, continuous glucose monitors (CGMs), insulin delivery systems, sleep monitors, and smart implants. Its highly sensitive radio is optimized to function while operating in direct contact with the body, all within compact and complex form factors.
 
The BG29 small Bluetooth microcontroller is equipped with several features optimized for miniaturized devices and wearables. The BG29 is extremely compact, available in QFN and WLCSP packages, with the WLCSP package occupying only 2.6 x 2.8 mm of footprint. This makes the BG29 one of the smallest, most secure, and powerful wireless MCU solutions on the market. The WLCSP package is ideal for tiny devices, including insulin delivery patches, sleep monitoring devices, continuous glucose monitors (CGMs), and smart tooth implants. The QFN package, on the other hand, is optimized for non-size-constrained health devices such as pulse oximeters and heart rate monitors.
 
The human body is one of the most complex design challenges for medical device makers. It absorbs and reflects radio signals and disturbs antenna resonance, especially for small wearable devices subject to strict regulatory guidance and specific absorption rate (SAR) limits. The BG29 features best-in-class radio sensitivity of -99.2 dBm, which is the most important characteristic for sending and receiving Bluetooth messages in in-body and on-body applications while saving device energy and battery.
 
With its high memory capacity of 1 MB Flash, 256 kB RAM, and 76.8 MHz ARM® Cortex®-M33 processor, the BG29 delivers superior processing capabilities for advanced applications with low power consumption. It has ample computing power to crunch complex algorithms while the large memory keeps data tracking going even during long smartphone connection breaks.
 
The integrated DCDC Boost on BG29 provides medical device makers with a wide voltage range, enabling single-cell alkaline and button cells, 1.5V silver oxides, and other chemistries, reducing battery and device sizes. The integrated Coulomb Counter (available only in Buck mode) enables accurate battery level monitoring on medical devices to avoid unexpected battery depletion during critical health application usage, enhancing the user experience.
 
Additionally, the BG29 is highly secure, which is critical in the medical and health segments. Silicon Labs Secure Vault™ solution with Virtual Secure Engine protects devices and users against scalable local and remote software and hardware attacks by providing advanced encryption, secure key management, and authentication.

Beyond the BG29, Silicon Labs offers a range of Bluetooth wireless SoCs to meet diverse customer needs. For example, the Silicon Labs BG24 Bluetooth SoC provides device makers with an integrated AI/ML accelerator that delivers faster and more power-efficient ML inferencing, eliminating the need for an external ML processor on the board.
 
Several Silicon Labs Bluetooth SoCs also feature an integrated ADC with high resolution of 12, 16, and 20 bits, saving costs, footprint, design, and testing effort. Additionally, compared to many competing solutions, Silicon Labs' Bluetooth solutions deliver a higher effective number of bits (ENOB) for ADCs, enabling more effective sampling. The Silicon Labs BG24 integrates an ADC and DAC that can be coupled with external Operational Amplifiers to form a complete Analog Front End, reducing cost, space, and integration complexity on CGM devices.
 
To address the power boost and buck requirements of wireless healthcare devices, Silicon Labs BG27 integrates both DC-DC converters directly. Ultra-low power consumption, both during operation and in optimized sleep modes (EM2), combined with the 1.5V supply through the DC-DC Boost provided in the BG27, allows a device to be fitted with an extremely small 1.5V silver oxide battery, minimizing the overall device form factor. Additionally, the BG27 integrates a Coulomb Counter, effectively reducing component count and eliminating the need for additional external components on the board.
 
Furthermore, Silicon Labs BG22 and BG27 feature an internal 32 kHz Low-Frequency RC Oscillator (LFRCO) that can self-calibrate against the HFXO on the device to meet Bluetooth LE requirements. As a result, unless the application requires higher clock accuracy, device makers can eliminate an external low-frequency crystal on the board, freeing up space and BoM costs.
 
Silicon Labs reference radio board designs typically use an extensive number of components and multiple layers for RF and V_DD filtering to provide device makers with the best possible RF performance even at the highest output power levels. By optimizing the RF performance of BG22, BG24, and BG27 SoCs to match ETSI and FCC regulations for low-power devices, you can reduce the number of bypass capacitors, filters, and the antenna matching network by a total of up to 6-14 components, decreasing footprint and BoM costs while still supporting ETSI/FCC requirements.

Designing small Bluetooth healthcare devices and wearables is a precision engineering challenge that seeks optimal solutions across multiple dimensional constraints - from PCB layouts measured in millimeters, to power control at the microwatt level, to complex RF challenges in the human body environment. Every trade-off directly impacts clinical usability and patient safety. Silicon Labs' Bluetooth SoC series is built precisely to address these needs. As the IoMT market continues to expand, wireless connectivity will penetrate more body-worn, implantable, and even single-use medical scenarios. We hope these technologies will help innovators overcome design hurdles, bringing the next disruptive medical device from imagination to reality, and creating a safer, smarter future for global health and well-being.