ROHM develops sensor IC for high-speed heart rate measurement for determining blood pessure, stress and vascular age


Class-leading detection accuracy and low power consumption - Supports the increasing demand for vital sign sensing

ROHM is offering an optical heart rate sensor for smart bands and watches, which, thanks to its high-speed 1024 Hz sampling, can be used for measuring blood pressure, stress and vascular age. The BH1792GLC is the second pulse wave sensor to be developed by ROHM. It is notable for its high detection accuracy and low power consumption of only 0.44mA during measurement. The 1024Hz sampling rate makes it possible to measure the heart rate up to 32 times faster than conventional solutions.

The BH1792GLC measures just 2.8mm x 2.8mm x 0.9mm (W x D x H). In addition to measuring the heart rate, an infrared sensor makes it possible to detect when the device is being worn. An integrated FIFO (First In First Out) memory helps to reduce the power consumption on the host side (MCU), which in turn decreases the power consumed by the sensor and increases the application drive time. The heart rate sensor works with supply voltages from 2.5V to 3.6V. Its operating temperature range is between -20°C and +85°C. The BH1792GLC is the ideal solution for smart bands, watches, smartphones and other portable devices requiring vital sign sensing. Samples and OEM quantities of the BH1792GLC have been available since December 2017.

An evaluation board (BH1792GLC-EVK-001) for use with the heart rate sensor is available from the online distributors Chip One Stop, Zyco Store (Core Staff) and RS Components, which can be connected via the ROHM sensor shield with open platform MCU boards such as Arduino Uno.

Background information

Recent years have seen a growing demand for wearables that can measure not only heart rate, but vital signs as well such as stress and vascular age in order to monitor and manage patient health. However, measuring complicated vital signs requires an increase in sampling frequency along with the number of measurements per unit of time, which can lead to higher power consumption and decreased battery life.

In response, ROHM has drawn on its wealth of expertise in optical sensors to develop a low-power heart rate sensor that facilitates high accuracy measurement even under strong IR conditions such as direct sunlight or during intense activities. Thanks to its high sampling rate, the new sensor meets the continuously developing needs of the IoT and wearable markets.

Also in future, ROHM will continue to develop solutions that ensure greater safety and convenience in wearables and other portable applications.

Key features

1. Meets the growing demand for vital sign sensing

The high-speed 1024Hz sampling rate makes it possible to measure more complicated vital signs like stress and vascular age. Furthermore, an infrared sensor is built in for sensing when the device is worn, simplifying system configuration by integrating this necessary component.

2. Optical filter achieves high accuracy detection

An optimised optical filter structure with integral infrared-cut and green filters, which only allow light with green wavelengths to pass through, reduces the susceptibility to external noise such as IR and red light by up to 10x compared with conventional solutions. This facilitates high accuracy detection even under noisy IR conditions.

3. Low power consumption contributes to long battery life

When combined with ROHM's green LED (SMLMN2ECT), which has been optimised for the light receiving characteristics of the heart rate sensor, the improved optical design makes it possible to achieve low current consumption of 0.44 mA (during pulse measurement).

In addition, a new FIFO function (First In First Out) function has been incorporated, which reduces the power consumption on the host side (MCU), decreasing the power consumed by the pulse sensor whilst contributing to longer battery life.

4. Optional evaluation board facilitates introduction

A pulse sensor evaluation board (BH1792GLC-EVK-001) is available through online distributors such as Chip One Stop, Zyco Store (Core Staff) and RS Components. This can be connected via ROHM's sensor shield (SensorShield-EVK-001) with open platform MCU boards such as Arduino Uno.