The small-footprint Si1144 sensor module integrates an optical sensor, green light-emitting diode (LED), LED drivers supporting up to two external LEDs, analog-to-digital converter (ADC), control logic and an I2C digital interface.

According to Silicon Labs’ market estimates, 100 million units of HRM-enabled devices will be sold per year by 2018, with the majority of those units being wrist-based wearables.

Silicon Labs’ Si1144 HRM solution addresses this large and growing market across a wide range of wearables including activity-tracking fitness bands, pedometers and smart watches, in addition to providing HRM capabilities for gym fitness equipment, bathroom scales and geriatric monitoring devices.

Heart rate monitoring is one of the most sought-after biometric sensing technologies available today for people of all fitness levels, from serious athletes looking to improve athletic performance to people simply seeking a healthier, more active lifestyle. Accurate HRM enables precise calculation of expended calories, making it easier to maintain dieting regimens.

Traditionally, heart rate measurement has been limited to the use of chest straps linked to an external device, such as a specialized fitness watch or a smartphone. These HRM solutions pose unique problems: chest straps are often inconvenient and uncomfortable to wear while smartphones can be difficult to monitor when running or cycling.

Wrist-based HRM technology changes the biometric monitoring game by providing a more convenient, comfortable way to measure heart rate rivaling the accuracy of chest-strap-based designs. The measured results vary widely, and many of these HRM solutions are costly as well as power hungry, reducing battery life. Complex motion artifacts also combine to make wrist-based HRM a complicated design challenge.

Features:

－ Accurate sensing of weak blood flow signals on the wrist with exceptional performance rivaling chest strap HRM designs

－ Choice of two algorithms to support static HRM and optional dynamic (motion-compensated) HRM using data from an external accelerometer

－ HRM solution pairs optical module with a Pearl Gecko MCU containing a DSP-enabled ARM Cortex-M4 core for low-power, high-performance designs or with a Cortex M3-based Jade Gecko MCU for simpler, cost-sensitive designs

－ Fully integrated HRM IC with green LED lens, high-sensitivity photodiode, low-noise ADC, LED drivers, optical blocking and host communications/interrupts

－ Two LED drivers to support up to two external LEDs

－ Ultra-low power consumption for long battery life in wearables: < 500 nA standby current with 1.71 V to 3.6 V supply voltage

－ I2C serial communications with up to 3.4 Mbps data rate

－ 10-lead 4.9 x 2.85 x 1.2 mm LGA module package