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 I2 C 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.