The healthcare sector has been adopting greater use of digital technology over the last two decades. The COVID-19 pandemic helped accelerate this evolution. The remote access to healthcare necessitated by the pandemic highlighted other benefits, such as more efficient healthcare delivery and continuous patient monitoring. Technological advances have given rise to the Internet of Medical Things (IoMT), in which networks of patients with portable or wearable medical devices and sensors, and corresponding healthcare systems and providers, are connected via Internet. Continuous blood glucose levels and cardiac monitors are examples of devices that have gained wide acceptance. IoMT devices help automate data transfer, thereby reducing human errors. Advances in predictive data analytics and artificial intelligence (AI) make IoMT devices even more powerful by enabling data-driven diagnoses with early detection of anomalies, increased patient self-engagement, and reduced healthcare costs.
Key requirements of IoMT devices
- Safety: The sensitive nature of the medical information being transferred requires a high level of security. Advanced Encryption Standard (AES) and Elliptic Curve Cryptography (ECC) can encrypt and decrypt data transfer using secure keys, thereby authenticating the data. Keys based on a true random number generator (TRNG) on the device help in the secure generation of these keys. Spoofing attacks can be minimized with the use of device identification using unique physically unclonable functions (PUFs) within the semiconductor device. Secure boot hardware protocols, as well as tamper-proof mechanisms that prevent access to protected regions of device memory, help improve device security.
- Energy consumption: Wearable and wearable devices are often battery-powered. Low-power communication protocols such as Bluetooth LE 5.x, power-saving modes when the device is not active, and an efficient architecture that optimizes operating performance versus power consumption are some essential features that can maximize battery life. .
- Rich feature set in a small footprint: The small and lightweight devices allow their use in portable medical applications. New applications such as smart tooth implants require tiny form factors. The systems-on-chip (SoC) concept offers a high level of multifunctional integration on a single chip. It may include a set of peripheral functions that provide high-speed analog and digital sensing, measurement, data transformation and communication. Other essential requirements are wireless connectivity, high-speed data processing with large Flash and RAM memories, low-frequency/low-power precision clocks and timers, DC/DC voltage regulation, etc.
Silicon Labs Gecko EFRBG27 Wireless SoC Family for IoMT Applications
In March 2023, Silicon Labs announced the launch of a new family of secure, low-power devices that expand its Wireless Gecko portfolio. This includes the BG27 series of Bluetooth LE SoC devices, ideal for IoMT applications.
Figure 1 shows a block diagram illustrating the broad set of features included in the BG27 SoCs. Below are some of its main features:
Figure 1: Features of Gecko's EFR32BG27 wireless SoC family. (Image source: Silicon Labs)
- Processor and memory: 33 MHz 76.8-bit ARM Cortex® M32 RISC core with DSP instruction and floating point unit enables high-performance signal processing capability at 1.50 Dhrystone MIPS/MHz. Includes ARM TrustZone security technology. The Flash memory is 768 kB, while the data memory is 64 kB of RAM. The Linked Direct Memory Access (LDMA) controller enables the system to perform software-independent memory operations, reducing power consumption and software workload.
- low power modes: The EFR32BG27 includes a power management unit (EMU) that manages the power mode transitions (EM0 to EM4) of the system-on-chip (SoC). With UEM, applications can dynamically minimize power consumption during program execution. EM0 mode offers the most features, such as triggering the CPU, radio, and peripherals at the highest clock frequency. Peripherals can be disabled in active low power modes EM2, EM3. EMU uses voltage scaling when switching from one power mode to another to optimize energy efficiency by operating at lower voltages whenever possible. EM4 is a low-power idle state that allows the system to wake up in EM0 mode.
- DC/DC conversion: The EFR32BG27 family includes buck and boost mode on-chip converters that can supply the necessary internal 1.8 V. Boost mode devices, such as the EFR32BG27C230F768IM32-B, have the ability to operate at 0.8 V, allowing operation with single-cell alkaline, silver oxide, and other low-voltage batteries. The boost converter can be disconnected via a dedicated BOOST_EN pin/pin, thereby saving system battery power during storage and transportation. In this mode, the maximum current consumption is only 20/50nA, depending on the power supply of certain pins. In buck mode devices, such as the EFR32BG27C140F768IM40-B, a maximum of 3.8 V can be supplied externally. An on-chip power monitor warns when the power is low enough to allow bypassing the regulator and extending the range to 1.8 V. Bypass mode also allows the system to go into EM4 power saving mode. A coulomb counter block is integrated into the DC/DC converter. It includes two 32-bit counters that are used to measure the number of charge pulses delivered by the DC/DC converter, allowing accurate monitoring of the battery level to improve user safety.
- Bluetooth 5.x networks: This SoC family supports the Bluetooth Low Energy (LE) wireless protocol. The radio receiver uses a low-noise architecture composed of a low-noise amplifier and I/Q downconversion. The Automatic Gain Control (AGC) module adjusts receiver gain to prevent clipping and improve selectivity and blocking. The 2.4 GHz radio is calibrated in production to improve image rejection performance. The family includes a range of transmit powers from 4 dBm to 8 dBm. RF noise mitigation includes operating the DC/DC converter in soft switching mode during startup and transitions from DC/DC regulation to shunt to limit the maximum slew rate of the supply and mitigate inrush current. The RFSENSE block allows the device to remain in EM2, EM3, or EM4 power saving modes and activate when radio frequency (RF) energy above a specified threshold is detected.
- Safety: The EFR32BG27 SoC family includes a number of security features, as shown in Figure 2.
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Figure 2: Security features of the Gecko EFR32BG27 family of wireless SoCs. (Image source: Silicon Labs)
Secure Boot with Trusted Root and Secure Loader (RTSL) authenticates trusted firmware from immutable read-only memory (ROM). Crypto Accelerator supports AES and ECC encryption and decryption. It also includes differential power analysis (DPA) countermeasures to protect keys. The TRNG collects entropy from a thermal source and includes startup state tests for this source, as required by NIST SP800-90B and AIS-31, as well as online state tests, as required by NIST SP800 -90C. The debug interface, locked when the part is released into the field, has a secure unlock feature that allows authenticated access based on public key cryptography. In terms of hardware, an external tamper detection module (ETAMPDET) allows detecting external tampering, such as unauthorized opening of the cabinet/enclosure. You can generate an interrupt to alert the software and allow system-level action to be taken.
- Extensive set of peripherals: SoCs include hybrid analog-to-digital converters that combine SAR and Delta-Sigma techniques. The 12-bit mode can operate at speeds up to 1 Msps, while the 16-bit converter can operate at 76,9 ksps. The analog comparator module can use internal or external references and can also be used to detect the supply voltage. Supports SPI, USART and I2C serial communication modes. The Real Time Clock and Capture (RTCC) module provides 32-bit timing up to EM3 power modes and can be synchronized with the internal low frequency oscillator. The Low Power Timer (LETIMER) offers 24-bit resolution and can be used for timing and generating outputs when the majority of the device is off, allowing simple tasks to be performed with minimal power consumption. The Peripheral Mirroring System (PRS) is a signal routing network that allows direct communication between peripheral modules without the intervention of the CPU. This reduces software overhead and current consumption.
- Small Footprint Packages: One of the devices in the EFR32BG27 family is the EFR32BG27C320F768GJ39-B. This device comes in a wafer-level chip-scale package (WLCSP) with dimensions of just 2.6 mm x 2.3 mm and can operate in buck or step-up mode. The rest of the family comes in 32mm x 4mm QFN4 or 40mm x 5mm QFN5 packages in specific buck or boost regulator modes.
Conclusion
The EFR32BG27 offers industry-leading low-power processing capability and Bluetooth Low Energy connectivity. These small form factor SoCs, which include various security features, are ideal for IoMT applications.
