As people increasingly focus on their health and many countries face the challenges of an aging population, the demand for medical wearable devices is rapidly increasing. These wearable devices typically operate on batteries, which require low power consumption and small form factors, posing challenges for the design of such products. This article will introduce you to the design requirements of medical wearable devices and the relevant solutions offered by onsemi.
Medical wearable devices aim for space miniaturization
The design requirements for medical wearable devices may vary depending on different application scenarios and target users. However, in general, they typically pursue space optimization and device miniaturization. To enhance wearer comfort and convenience, medical wearable devices should minimize size and weight as much as possible and integrate various functions and communication circuits using miniature components and systems.
To meet diverse functional requirements, medical wearable devices should employ flexible circuit technology, allowing the device to conform to the wearer's body contours and improve design flexibility and reliability. On the other hand, the primary purpose of medical wearable devices is to transmit accurate physiological data to healthcare providers rapidly and promptly. Therefore, in the design, it is essential to ensure both sufficient power and high signal integrity. This requires the use of efficient power designs, board-to-board connectors, FPC connectors, and appropriate signal processing and transmission algorithms.
As medical wearable devices are products involving human health and safety, they must comply with relevant regulations and standards, such as the US FDA, EU CE, etc. This necessitates conducting risk assessments and test validations during the design phase to ensure product quality and efficacy, in accordance with medical regulations and safety standards.
A complete solution for low-power wearable devices
onsemi incorporated feedback from implantable medical device customers into the design of RSL10. These customers require devices to operate for many years on small batteries without recharging. For wearable device applications, onsemi's RSL10 Bluetooth® Low Energy (Bluetooth LE) device offers ultra-low power characteristics. In sleep mode, all products in the RSL series can operate at very low duty cycles, with power consumption in the nA range.
Applications like hearing aids that involve audio require an audio codec. RSL10 integrates LPDSP32, capable of running audio codecs such as G.722 or CELT. The LPDSP32 processor is a dedicated hardware block designed for the most efficient, low-power compression/decompression of audio data. omsemi's EZAIRO® 7160 wireless pre-configured DSP with RSL10 is an ideal choice for small form-factor, low-power audio applications like hearing aids.
Wearable devices typically have strict size requirements. Choosing a WLCSP (wafer-level chip scale package) silicon die, with solder balls for connections, is ideal for applications that require minimal form factors, such as consumer electronics, medical disposables, wearables, or ID tags. The RSL10 WLCSP has a tiny size of 2.32 mm x 2.36 mm with a thickness of only 0.35 mm. The RSL10 QFN package measures 6 mm x 6 mm, and the RSL15 QFN package is 5 mm x 5 mm, all very compact.
Developing any RF system comes with the added complexity of choosing the surrounding components and antenna to match the hardware environment. To meet the requirements of standards like FCC, CE, or other regulatory bodies, you can opt for a pre-certified module that integrates all the required passive components (e.g., crystals, power supply decoupling, and antenna matching circuits) and an integrated antenna. In this case, the RSL10 SIP is an ideal solution. It integrates all passive components and the antenna within a certified module measuring 6 mm x 8 mm x 1.46 mm.
onsemi, as a supplier of medical components, has a long history and applies this experience to design the MD-RSL10 for use in implantable or life-critical applications such as cardiac monitoring and management as well as neurostimulation.
To assist customers in accelerating product development, onsemi offers several validated reference designs that can serve as starting points for customer projects, expediting development. Reference designs typically include application hardware, firmware, bill of materials (BOM), schematics, and PCB manufacturing files. onsemi provides various low-power reference designs, including RSL10 Sensor Development Kit, RSL10 Asset Tag, Energy Harvesting Bluetooth Low Energy Switch, RSL10 Smart Shot Camera Platform, and Secure Transmission.
Developers must incorporate one or more security mechanisms when protecting sensitive data such as personal health information and payment transaction information. RSL15 includes the latest embedded security features, with a genuine hardware-based root of trust and Arm crypto-cell for hardware-accelerated cryptographic algorithms.
Remote monitoring devices are a common Internet of Things (IoT) application where the device remains in sleep mode most of the time, occasionally waking up to transmit a few data packets before returning to sleep. RSL15 is well-suited for such applications as it offers multiple low-power modes to fit almost any application's requirements.
Low-power wireless radio system on chip supporting multiple protocols
RSL10 is a Bluetooth 5.2, multi-protocol wireless radio system-on-chip (SoC) that enables ultra-low-power wireless applications. RSL10 achieves industry-leading low power consumption, with 62.5nW in deep sleep mode, 7mW in receive mode, while optimizing system size and battery life to support various advanced wireless features. This highly integrated wireless SoC features a dual-core architecture and a 2.4GHz transceiver, offering flexible support for both Bluetooth Low Energy and 2.4 GHz custom protocols, and it supports firmware over-the-air (FOTA) updates.
RSL10 operates within a flexible voltage range (1.1V to 3.3V), making it suitable for devices powered by 1.2V and 1.5V batteries without the need for an external DC/DC converter. It comes in a 5.50 mm2 WLCSP and 6 x 6 mm QFN package. For even smaller form factors, the wireless SoC also offers a full System-in-Package (SiP) solution.
RSL10 features a precision dual-core structure with a programmable Arm Cortex-M3 processor with a clock speed of up to 48 MHz, providing flexible support for 2.4 GHz proprietary and custom protocol stacks. An embedded digital signal processor (DSP) supports signal processing-intensive applications like wireless audio encoding and decoding.
RSL10's on-chip and software wireless support includes a 2.4 GHz Radio Frequency Front-End (RFFE) and a Bluetooth 5.2-certified baseband controller that supports data rates of up to 2 Mbps. The RSL10 development toolkit offers various Bluetooth Low Energy profiles. This highly integrated SoC includes a robust dual-core architecture, efficient power management unit, oscillators, flash and RAM memories, DMA controller, as well as peripherals and interfaces, and features 384kB of embedded flash with IP protection to secure flash contents, along with configurable analog and digital sensor interfaces (GPIO, LSAD, I2C, SPI, PCM).
RSL10 is well-suited for medical wearable devices, common end products of which include fitness trackers/activity monitors, smartwatches, hearing aids/hearables devices, heart rate monitors, blood glucose monitors (BGM), continuous glucose monitors (CGM), and pulse oximeters, among others.
The RSL10 Software Development Kit (SDK) is based on the free onsemi Integrated Development Environment (IDE) for Eclipse® and supports Keil μVision® and IAR Embedded Work Bench®. It provides a complete Bluetooth Low Energy protocol stack, supports Android and iOS applications (firmware over-the-air updates), and offers FreeRTOS™ support.
A wireless microcontroller and audio processor that meet the requirements of medical smart connected devices
onsemi's RSL15 is a low-power, secure Bluetooth Low Energy 5.2 wireless MCU based on the Arm® Cortex®−M33 processor, designed for intelligent connected devices in industrial and medical applications. RSL15 features built-in power management, a wide voltage range, flexible GPIO and clock schemes, and an extensive set of peripherals, providing maximum design flexibility for high-performance and low-power applications. RSL15 comes with 80kB of RAM and offers two flash options: 284kB or 512kB. It is primarily used in industrial automation and sensing, connected medical IoT sensors, wearables, asset tracking, electronic tags and access control, electronic labels, data loggers, smart appliances, energy harvesting switches, and more.
RSL15 is an industry-leading general-purpose MCU and the lowest-power flash-based secure Bluetooth Low Energy MCU in the industry. It incorporates the latest embedded security technologies with Root of Trust, supports Bluetooth Low Energy 5.2 with long-range and localization capabilities, and offers a comprehensive and user-friendly software development kit (SDK). This SDK includes drivers, libraries, sample code, development tools, and mobile apps, supporting both iOS and Android, with RSL15 Central and RSL FOTA for iOS and Android.
onsemi also provides a wireless feature DSP audio processor for hearing aids called EZAIRO 7160 SL. Ezairo 7160 SL enables wireless connectivity in hearing aids and is a programmable, DSP-based hybrid module supporting Bluetooth Low Energy and other 2.4 GHz wireless protocols.
The device includes the Ezairo 7100 digital signal processor (DSP), featuring a high-precision, quad-core architecture delivering 375 MIPS without sacrificing power performance. It interfaces seamlessly with the RSL10 radio integrated circuit, which is Bluetooth 5 certified and has the industry's lowest power consumption for wireless sensing. Ezairo 7160 SL also includes EA2M, a 2 Mb EEPROM memory for storing important hearing aid parameters and firmware. Development tools such as the Ezairo pre-configuration suite, open-programming evaluation and development kit (EDK), and more are provided. Ezairo 7160 SL can be used for wireless connectivity, audio processing, stereo audio streaming, Bluetooth Low Energy control, and is most commonly used in hearing aids.
Conclusion
The design of medical wearable devices pursues low power consumption, small form factors, and compliance with safety regulations. Therefore, highly integrated low-power components are essential to meet the stringent requirements of medical wearable devices. onsemi offers a variety of medical component solutions tailored for medical wearable devices, including system-on-chip wireless systems, microcontrollers, wireless Bluetooth chips, and audio processors. These solutions are characterized by high integration, low power consumption, and compact size. They also come with comprehensive software and hardware development tools, making onsemi an ideal partner for developers of related products.