A reference design for heart rate monitoring solution on wearable devices from Taiwanese IC design house Weltrend Semiconductor has been adopted by a major ODM inside its golf smartwatch.

The smartwatch combines golf trainer, activity tracking, built-in green light heart rate sensor, GPS and Bluetooth functions. It is the first golf smartwatch with heart rate measurement, according to the ODM, and is available for sale at online retailers such as Amazon.

The reference design combines Weltrend Semiconductor's WTHRM122 heart rate monitoring MCU with analog front-end (AFE) with New Japan Radio's optical sensor and ROHM's KXTJ2-1009 accelerometer, according to Weltrend.

Weltrend’s WTHRM122 is a heart rate monitoring MCU, using PPG (Photoplethysmographic) technology, for the application of continuous heart rate measurement. It includes CPU, flash memory, SRAM, ADC, filters, amplifiers, LED intensity control circuits, serial interfaces and internal oscillator.

PPG is a non-invasive technique which is especially suitable for wearable technologies/devices. With Weltrend’s automatic motion artifact removal algorithm, WTHRM122 could be used on wearable devices such as smartwatch, sport watch or bracelet to continuously detect, measure, calculate and display heart rate during exercise, walking and running.

ROHM (Kionix)’s KXTJ2-1009 is one of the company’s smallest tri-axis accelerometers, designed for mobile/wearable applications. It offers excellent power performance along with an embedded motion wake-up feature, fast-mode I2C and up to 14-bit resolution. The KXTJ2-1009 is delivered in a 2mm x 2mm x 0.9mm, 12-pin, LGA package with an operating temperature range of -40°C to 85°C.

The KXTJ2-1009 sensor offers improved shock, reflow and temperature performance, and the ASIC has internal voltage regulators that allow operation from 1.8V to 3.6V within the specified product performance.