GENERAL DESCRIPTION

The ADXL3121 is a small, thin, low power, 3-axis accelerometer

with high resolution (13-bit) measurement up to ±12 g. Digital

output data is formatted as 16-bit twos complement and is

accessible through either a serial port interface (SPI) (3- or 4-wire)

or I2C digital interface.

The ADXL312 is well suited for car alarm or black box applications.

It measures the static acceleration of gravity in tilt-sensing

applications, as well as dynamic acceleration resulting from motion

or shock. Its high resolution (2.9 mg/LSB) enables resolution of

inclination changes of as little as 0.25°. A built-in FIFO facilitates

using oversampling techniques to improve resolution to as

little as 0.05° of inclination.

Several special sensing functions are provided. Activity and

inactivity sensing detects the presence or absence of motion and

whether the acceleration on any axis exceeds a user-set level.

These functions can be mapped to interrupt output pins. An

integrated 32 level FIFO can be used to store data to minimize

host processor intervention.

Low power modes enable intelligent motion-based power

management with threshold sensing and active acceleration

measurement at extremely low power dissipation.

The ADXL312 is supplied in a small, thin 5 mm × 5 mm ×

1.45 mm, 32-lead, LFCSP package.

FEATURES

Ultralow power: as low as 57 μA in measurement mode and

0.1 μA in standby mode at VS = 3.3 V (typical)

Power consumption scales automatically with bandwidth

User-selectable resolution

Fixed 10-bit resolution

Full resolution, where resolution increases with g range,

up to 13-bit resolution at ±12 g (maintaining 2.9 mg/LSB

scale factor in all g ranges)

Embedded FIFO technology minimizes host processor load

Built-in motion detection functions for activity/inactivity

monitoring

Supply and I/O voltage range: 2.0 V to 3.6 V

SPI (3- and 4-wire) and I2C digital interfaces

Flexible interrupt modes mappable to either interrupt pin

Measurement ranges selectable via serial command

Bandwidth selectable via serial command

Wide temperature range (−40 to +105°C)

10,000 g shock survival

Pb free/RoHS compliant

Small and thin: 5 mm × 5 mm × 1.45 mm LFCSP package

Qualified for automotive applications

APPLICATIONS

Car alarm

Hill start aid (HSA)

Electronic parking brake

Data recorder (black box)