Biosensors add ECG measurement for heart monitoring

Optical biometric sensors from Silicon Labs provide advanced heart rate monitoring (HRM) and electrocardiogram (ECG) capabilities for a range of wearable fitness and wellness products.

The Si117x sensor modules combine low power, high sensitivity and exceptional integration, says Silicon Labs, making them suitable for smart watches and wrist-based, patch-type and other wearables requiring long battery life and enhanced HRM accuracy.

To simplify development and speed time to market, Silicon Labs offers a complete, end-to-end sensing solution with the Si117x sensor module, HRM algorithm, Silicon ‘ Labs’ Wireless Gecko SoCs for Bluetooth connectivity, and awrist-based development kit with sample code and example projects.

By tracking the heart rate throughout the day, end users and health-care providers can analyse physiological patterns, detect health issues before they become problems and consider lifestyle adjustments. For power efficiency, the Si117x sensors consume less than 50-micro Amp (sensor and LED combined) while performing continuous heart rate monitoring. A built-in buffer and accelerometer synchronisation save even more system-level power, says Silicon Labs. The sensors’ industry-leading power efficiency enables developers to use smaller batteries in wearable designs without significantly impacting the device’s battery life during continuous monitoring.

The Si117x sensors offer fast sampling speeds, a high signal-to-noise ratio (SNR) above 100dB. They also cancel out ambient noise and erroneous data, resulting in high-quality signals that make it easier to track heart rates despite challenging physiologies, varying skin tones and the presence of tattoos, explains Silicon Labs. A more accurate view of the heart rate waveform enables biometrics beyond traditional monitoring, including heart rate variability (HRV), stress analysis and pulse volume.

The Si117x sensors bring ECG waveform capability to wrist-based wearables in a cost-effective, power-efficient manner, says Silicon Labs. By making measurements in the same device and simultaneously, the Si117x sensors allow developers to combine biometrics with optical photoplethysmogram (PPG) measurements to derive valuable physiological parameters.

The Si117x module’s high level of integration simplifies wearable design and makes it easier to synchronise multiple sensor measurements without adding significant system cost or board area. Each module supports up to four distinct LEDs (all of which can be driven simultaneously). The module’s four LED drivers are independently programmable (from 1.7 to 310mA). Additional built-in features include a photodetector, 24-bit ADC with up to 100dB dynamic range, I²C and SPI digital interfaces, programmable event interrupt engine, synchronisation engine, host communications processor and inputs for two external photodiodes.

The Si117x sensors support Silicon Labs’ proprietary, motion-compensated HRM algorithm optimized for wrist-based sensing and to run on EFM32 Gecko MCUs and EFR32 Wireless Gecko SoCs supporting Bluetooth Low Energy.

Samples and volume quantities of the Si117x sensors are available in a 3.7 x 7.0mm 28-pin LGA module. Silicon Labs also offers Si118x optical biometric sensors with an integrated photodiode in a clear 3.0 x 3.0mm QFN package. To simplify development and performance evaluation, there is a variety of wrist-based ECG and PPG development kits, a Bluetooth-enabled HRM evaluation watch, and an Android-based Triple Heart Application that captures data from multiple devices.

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