Datasheet

MMA8451Q

Sensors

12 Freescale Semiconductor, Inc.

5 Functionality

The MMA8451Q is a low-power, digital output 3-axis linear accelerometer with a I

C interface and embedded logic used to

detect events and notify an external microprocessor over interrupt lines. The functionality includes the following:

• 8-bit or 14-bit data, High-Pass Filtered data, 8-bit or 14-bit configurable 32 sample FIFO

• Four different oversampling options for compromising between resolution and current consumption based on application

requirements

• Additional Low Noise mode that functions independently of the Oversampling modes for higher resolution

• Low Power and Auto-WAKE/SLEEP modes for conservation of current consumption

• Single/Double tap with directional information 1 channel

• Motion detection with directional information or Freefall 1 channel

• Transient/Jolt detection based on a high-pass filter and settable threshold for detecting the change in acceleration above

a threshold with directional information 1 channel

• Flexible user configurable portrait landscape detection algorithm addressing many use cases for screen orientation

All functionality is available in 2g, 4g or 8g dynamic ranges. There are many configuration settings for enabling all the different

functions. Separate application notes have been provided to help configure the device for each embedded functionality.

5.1 Device Calibration

The device interface is factory calibrated for sensitivity and Zero-g offset for each axis. The trim values are stored in Non

Volatile Memory (NVM). On power-up, the trim parameters are read from NVM and applied to the circuitry. In normal use, further

calibration in the end application is not necessary. However, the MMA8451Q allows the user to adjust the Zero-g offset for each

axis after power-up, changing the default offset values. The user offset adjustments are stored in 6 volatile registers. For more

information on device calibration, refer to Freescale application note, AN4069.

Table 8. Features of the MMA845xQ devices

Feature List MMA8451 MMA8452 MMA8453

Digital Resolution (Bits) 14 12 10

Digital Sensitivity (Counts/g) 4096 1024 256

Data-Ready Interrupt Yes Yes Yes

Single-Pulse Interrupt Yes Yes Yes

Double-Pulse Interrupt Yes Yes Yes

Directional-Pulse Interrupt Yes Yes Yes

Auto-WAKE Yes Yes Yes

Auto-SLEEP Yes Yes Yes

Freefall Interrupt Yes Yes Yes

32 Level FIFO Yes No No

High-Pass Filter Yes Yes Yes

Low-Pass Filter Yes Yes Yes

Orientation Detection Portrait/Landscape = 30°, Landscape to Portrait = 60°,

and Fixed 45° Threshold

Yes Yes Yes

Programmable Orientation Detection Yes No No

Motion Interrupt with Direction Yes Yes Yes

Transient Detection with High-Pass Filter Yes Yes Yes

Low Power Mode Yes Yes Yes