原标题：Freescale MMA845X三轴14位数字加速度计解决方案

　　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1.MMA8451Q方框图

　　图2.MMA8451Q应用框图

　　LFSTBEB845X: MMA845X 传感器加速度计板

　　The LFSTBEB845X is an evaluation board for the Freescale MMA845X family of 3-axis high performance, high functionality low-g accelerometers. The LFSTBEB845X kit includes daughter boards for each of the three devices in this family: MMA8451Q, MMA8452Q, and MMA8453Q. For customers already familiar with the Sensor Toolbox Platform, the LFSTBEB845X is designed to work with the LFSTBBAT9 for power or LFSTBUSB for communication to a PC.

　　The development kit RDMMA845X comes with both the LFSTBEB845X and the LFSTBUSB boards together for evaluating all of the embedded MMA845X functionality.

　　LFSTBEB845X 包括:

　　One Accelerometer Development Board

　　One MMA8451 Daughter Board

　　One MMA8452 Daughter Board

　　One MMA8453 Daughter Board

　　USB Cable

　　Quick Start Guide

　　图3.LFSTBEB845X传感器加速度计板外形图

　　图7. MMA8451Q电路图

　　图8. MMA8452Q电路图

　　图9. MMA8453Q电路图