摘要：  本文介绍了MMA8451Q主要特性， 方框图， 应用框图以及MMA845X 传感器加速度计板LFSTBEB845X电路图和元件布局图.

关键字：  智能，  电脑，  阅读器，  计步器，  传感器，  

 Freescale公司的MMA8451Q是14位/8位智能低功耗三轴数字加速度计，工作电压1.95V-3.6V，接口电压1.6V-3.6V，动态可选择满刻度为±2g/±4g/±8g，输出数据速率(ODR)从1.56 Hz 到800 Hz， 噪音为99 ug/√Hz，14位和8位数字输出，I2C数字输出接口，主要用在电子罗盘，静态方向检测，笔记电脑，电子阅读器，实时方向检测(如3D定位反馈)和实时行为分析(如计步器).本文介绍了MMA8451Q主要特性， 方框图， 应用框图以及MMA845X 传感器加速度计板LFSTBEB845X电路图和元件布局图.

 3-Axis， 14-bit/8-bit Digital Accelerometer

 The MMA8451Q is a smart low-power， three-axis， capacitive micromachined accelerometer with 14 bits of resolution. This accelerometer is packed with embedded functions with flexible user programmable options， configurable to two interrupt pins. Embedded interrupt functions allow for overall power savings relieving the host processor from continuously polling data. There is access to both low pass filtered data as well as high pass filtered data， which minimizes the data analysis required for jolt detection and faster transitions. The device can be configured to generate inertial wake-up interrupt signals from any combination of the configurable embedded functions allowing the MMA8451Q to monitor events and remain in a low power mode during periods of inactivity. The MMA8451Q is available in a 3 mm x 3 mm x 1 mm QFN package.

 MMA8451Q主要特性:

1.95 V to 3.6 V supply voltage

1.6 V to 3.6 V interface voltage

±2g/±4g/±8g dynamically selectable full-scale

Output Data Rates (ODR) from 1.56 Hz to 800 Hz

99 ug/√Hz noise

14-bit and 8-bit digital output

I2C digital output interface (operates to 2.25 MHz with 4.7 k ohm pull-up)

2 programmable interrupt pins for 7 interrupt sources

3 embedded channels of motion detection

– Freefall or Motion Detection: 1 channel

– Pulse Detection: 1 channel

– Jolt Detection: 1 channel

Orientation (Portrait/Landscape) detection with programmable hysteresis

Automatic ODR change for Auto-WAKE and return to SLEEP

32 sample FIFO

High Pass Filter Data available per sample and through the FIFO

Self-Test

RoHS compliant

Current Consumption: 6 uA–165uA

MMA8451Q典型应用:

E-Compass applications

Static orientation detection (Portrait/Landscape， Up/Down， Left/Right， Back/Front position identification)

Notebook， E-Reader and Laptop Tumble and Freefall Detection

Real-time orientation detection (virtual reality and gaming 3D user position feedback)

Real-time activity analysis (pedometer step counting， freefall drop detection for HDD， dead-reckoning GPS backup)

Motion detection for portable product power saving (Auto-SLEEP and Auto-WAKE for cell phone， PDA， GPS， gaming)

Shock and vibration monitoring (mechatronic compensation， shipping and warranty usage logging)

User interface (menu scrolling by orientation change， tap detection for button replacement)

图9. MMA8453Q电路图