Freescale MMA8451Q智能低功耗三轴加速度计解决方案

发布时间：2012-6-19 12:17 发布者：1770309616

Freescale 公司的MMA8451Q是智能低功耗三轴容性微机械数字加速度计,具有14位分辨率,3x3x1mmQFN封装,电源电压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 μg/√Hz ,定流消耗6 μA – 165 μA,主要用在电子罗盘,静态位置检测,笔记本电脑,电子书,实时位置检测,手持产品运动检测,震动和振动监测,用户接口等.本文介绍了MMA8451Q主要特性,框图,应用框图以及MMA845X系列传感器加速计工具箱LFSTBEB845X主要特性,电路图以及MMA8451/2/3Q电路图与PCB布局图.

MMA8451Q是一个智能低功耗，3轴，14位分辨率的，电容式微机械加速计。该加速度计具有很多灵活的，用户可编程选项，配置有两个中断引脚。其嵌入式中断功能可降低整体功耗，减轻主机处理器处理数据的负担。其接口可连接低通滤波数据，以及高通滤波数据，大限度地减少了颠簸检测和快速转换所需的数据分析。该设备可以配置为惯性唤醒，用以中断可配置嵌入式功能组合产生的信号，使得MMA8451Q在闲置期间进行监控，并保持在低功耗模式。MMA8451Q为3mm×3mm×1mm QFN封装。

图1 MMA8451Q方框图

图2 MMA8451Q应用框图

MMA8451Q主要特性

•1.95V~3.6V的电源电压

•1.6V~3.6V的接口电压

•±2G/±4G/±8全范围动态选择

•输出数据速率（ODR），从1.56Hz~800Hz

• 99μg/Hz噪声

• 14位和8位数字输出

• I2C数字输出接口（4.7kΩ上拉，2.25 MHz运作）

• 7个中断源的两个可编程中断引脚

•三通道嵌入式运动检测

•自由落体运动检测：1通道

•脉冲检测：1通道

•颠簸检测：1通道

•方向（纵向/横向）检测，可编程迟滞

•自动唤醒，并返回到睡眠的，自动ODR变化

• 32采样FIFO

•每个样品，通过FIFO，高通筛选数据

•自检

•符合RoHS标准

•电耗：6μA~165μA

MMA8451Q典型应用

• eCompass应用

•静态定位检测（人像/风景，上/下，左/右，后退/前位置识别）

•笔记本电脑，电子阅读器和笔记本电脑翻滚和自由落体检测

•实时定位检测（虚拟现实和游戏的3D用户位置反馈）

•实时活动分析（计步器步计数，为硬盘的自由落体跌落检测，航位推算GPS备份）

•便携式产品节电运动检测（手机自动休眠和自动唤醒，PDA，全球定位系统，游戏）

•冲击和振动监测（机电补偿，航运和保修使用率日志记录）

•用户界面（菜单滚动的方向变化，轻触按钮更换检测）

图3 LFSTBEB845x电路图(1)

图4 LFSTBEB845x电路图(2)

MMA845xQ 传感器工具箱

飞思卡尔MMA845xQ传感器工具箱加速计套件，为MMA845xQ加速计系列，提供了开发和示范的硬件和软件。

MMA845xQ 传感器工具箱包括:

• MMA845xQ评估板

• MMA8451Q加速度计子板

• MMA8452Q加速度计子板

• MMA8453Q加速度计子板

该套件需要LFSTBUSB USB接口板，以连接到个人电脑。如果您已经有了MMA8450Q加速计的RD3924MM450Q传感器工具箱，该USB板就在套件里。MMA845xQ套件的型号是LFSTBEB845x，USB接口板的型号是LFSTBUSB。

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 wakeup 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 by 3 mm by 1 mm QFN package.

MMA8451Q主要特性:

• 1.95V to 3.6V supply voltage

• 1.6V to 3.6V interface voltage

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

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

• 99 μg/√Hz noise

• 14-bit and 8-bit digital output

• I2C digital output interface (operates to 2.25 MHz with 4.7 kΩ pullup)

• Two programmable interrupt pins for seven interrupt sources

• Three 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 μA – 165 μA

MMA8451Q典型应用:

• eCompass applications

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

• Notebook, eReader 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系列传感器加速计工具箱

MMA845xQ 传感器工具箱

The Freescale MMA845xQ sensor toolbox accelerometer kit provides hardware and software for development and demonstration of the MMA845xQ family of accelerometers.

MMA845xQ 传感器工具箱包括:

• MMA845xQ evaluation board

• MMA8451Q accelerometer daughter board

• MMA8452Q accelerometer daughter board

• MMA8453Q accelerometer daughter board

The kit requires the LFSTBUSB USB-interface board to attach the kit to a personal computer. If you already have the RD3924MM450Q Sensor Toolbox, for the MMA8450Q accelerometer, the USB board is in that kit.

The MMA845xQ kit’s part number is LFSTBEB845x and the USB-interface board’s part number is LFSTBUSB.