IIS2DLPCTR datasheet(24/69 Pages) STMICROELECTRONICS

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Terminology and functionality

IIS2DLPC

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DocID031788 Rev 4

3.2.3

Self-test

The self-test allows checking the sensor functionality without moving it. The self-test

function is off when the self-test bits (ST) are programmed to ‘00’. When the self-test bits are

changed, an actuation force is applied to the sensor, simulating a definite input acceleration.

In this case the sensor outputs will exhibit a change in their DC levels which are related to

the selected full scale through the device sensitivity. When the self-test is activated, the

device output level is given by the algebraic sum of the signals produced by the acceleration

acting on the sensor and by the electrostatic test-force. If the output signals change within

the amplitude specified in Table 4, then the sensor is working properly and the parameters

of the interface chip are within the defined specifications.

3.2.4

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 INTERRUPTS_ENABLE bit in

CTRL7 (3Fh) and the SLEEP_ON bit in WAKE_UP_THS (34h), the IIS2DLPC automatically

goes to 12.5 Hz ODR in the low-power mode previously selected by the LP_MODE[1:0] bits

in CTRL1 (20h) if the sleep state condition is detected and wakes up as soon as the

interrupt event has been detected, increasing the output data rate and bandwidth.

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 the STATIONARY bit

in WAKE_UP_DUR (35h), the IIS2DLPC detects acceleration below a fixed threshold but

does not change either ODR or operating mode (High-Performance mode or Low-Power

mode) after sleep state detection.

The Activity/Inactivity recognition function can use the high-pass filter or the offset outputs,

this choice can be made through the USR_OFF_ON_OUT bit in CTRL7 (3Fh).

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

the threshold in WAKE_UP_THS (34h), the device goes into a sleep-to-wake state (as

wake-up).

For the activity/inactivity function, the device, in a wake-up state, will return to the operating

mode (HP or LP) and ODR before sleep state detection.

Activity/Inactivity, stationary/motion-detection threshold and duration can be configured in

the following control registers:

WAKE_UP_THS (34h)

WAKE_UP_DUR (35h)

IIS2DLPCTR 数据表(PDF) 24 Page - STMicroelectronics

IIS2DLPCTR 数据表(HTML) 24 Page - STMicroelectronics

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