H3LIS331DL datasheet(15/38 Pages) STMICROELECTRONICS

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H3LIS331DL

Functionality

The H3LIS331DL is a “nano”, low-power, digital output 3-axis linear accelerometer housed

in an LGA package. The complete device includes a sensing element and an IC interface

able to take the information from the sensing element and to provide a signal to the external

world through an I2C/SPI serial interface.

3.1

Sensing element

A proprietary process is used to create a surface micromachined accelerometer. The

technology allows processing suspended silicon structures, which are attached to the

substrate in a few points called anchors and are free to move in the direction of the sensed

acceleration. To be compatible with traditional packaging techniques, a cap is placed on top

of the sensing element to avoid blocking the moving parts during the molding phase of the

plastic encapsulation.

When an acceleration is applied to the sensor, the proof mass displaces from its nominal

position, causing an imbalance in the capacitive half bridge. This imbalance is measured

using charge integration in response to a voltage pulse applied to the capacitor.

At steady-state the nominal value of the capacitors are a few pF and when an acceleration

is applied, the maximum variation of the capacitive load is in the fF range.

3.2

IC interface

The complete measurement chain is composed of a low-noise capacitive amplifier which

converts the capacitive unbalancing of the MEMS sensor into an analog voltage that will be

available to the user through an analog-to-digital converter.

The acceleration data may be accessed through an I2C/SPI interface, making the device

particularly suitable for direct interfacing with a microcontroller.

The H3LIS331DL features a data-ready signal (RDY) which indicates when a new set of

measured acceleration data is available, therefore simplifying data synchronization in the

digital system that uses the device.

3.3

Factory calibration

The IC interface is factory calibrated for sensitivity (So) and zero-g level (TyOff).

The trim values are stored inside the device in non-volatile memory. Any time the device is

turned on, the trim parameters are downloaded into the registers to be used during active

operation. This allows the device to be used without further calibration.

H3LIS331DL Datasheet(PDF) 15 Page - STMicroelectronics