MEMS acceleration sensors for wearable devices

The new acceleration sensors from Bosch Sensortec include an optimised step counter for wearables integrated directly in the sensor, with no additional external microcontroller required. This helps reduce system cost and power consumption, reduces design complexity and thus speeds up time-to-market.

Typical applications for the BMA456 and BMA423 include step counting in wearables such as fitness bands. The sensors can also be used for advanced gesture recognition, such as tilting of the wrist, and can detect activities like running, walking and standing still.

The BMA456 provides the highest performance and accuracy of the family, with 16-bit resolution, noise of 120μg/√Hz, and a total offset over its lifetime of 20mg. Temperature Coefficient of Offset (TCO) is ±0.3mg/K, ensuring activity tracking remains accurate under all conditions.

The new Bosch acceleration sensors are housed in compact packages measuring 2.0x2.0mm. The BMA456 has a low height of only 0.65mm, which makes this sensor easy to design into space-constrained wearable applications such as fitness trackers, smartwatches, and hearables.

Power consumption of the step counter is low, typically less than 30μA, which helps maximise battery life in portable devices. The sensors can be used to put wearables into sleep mode even during step-counting, thereby helping to reduce overall power consumption.

These new sensors provide a complementary alternative to Bosch’s existing sensors for wearables and smartphones. For example, the BMA455 and BMA422 are ultra-small acceleration sensors with integrated Android features designed for low-power smartphone applications.