IIS2DULPX datasheet(23/106 Pages) STMICROELECTRONICS

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5.2

Activity/inactivity, stationary/motion detection functions

The activity/inactivity function recognizes the device’s sleep state and allows reducing system power

consumption.

When the activity/inactivity function is activated by setting the SLEEP_ON bit in WAKE_UP_THS (1Ch), the

device automatically goes to the inactivity output data rate selected by the INACT_ODR[1:0] bits in register

CTRL4 (13h).

With this feature the system may be efficiently switched from low-power mode to full performance depending on

user-selectable positioning and acceleration events, thus ensuring power saving and flexibility.

The stationary/motion detection function only recognizes the device’s sleep state.

When the stationary/motion detection function is activated by setting to a stationary condition the

INACT_ODR[1:0] bits in register CTRL4 (13h), the device detects acceleration below a fixed threshold but does

not change the ODR after sleep state detection.

The activity/inactivity recognition and stationary/motion detection functions are activated by writing the desired

threshold in the WAKE_UP_THS (1Ch) register. The high-pass filter is automatically enabled.

If the device is in sleep (inactivity/stationary) mode, when at least one of the axes exceeds the threshold in

WAKE_UP_THS (1Ch), the device goes into a sleep-to-wake state (as wake-up).

For the activity/inactivity function, the device, in a wake-up state, returns to the ODR before sleep state detection.

Activity/inactivity, stationary/motion detection threshold and duration can be configured in the following control

registers:

WAKE_UP_THS (1Ch)

WAKE_UP_DUR (1Dh)

IIS2DULPX

Digital main blocks and embedded low-power features

DS14580 - Rev 1

page 23/106

IIS2DULPX Datasheet(PDF) 23 Page - STMicroelectronics