The document discusses several low-g accelerometers from Freescale for measuring acceleration: - The MMA7260Q is an analog output accelerometer with selectable sensitivities of 1.5g, 2g, 4g, or 6g and low power consumption. - The MMA73xxL family also has analog outputs and includes models with sensitivities of 1.5g/6g, 3g/11g, and 4g/12g. - The MMA745xL has a digital I2C or SPI output, selectable sensitivities of 2g, 4g, or 8g, and interrupts for free fall detection. - Example applications discussed include adjusting sensitivity

1. Low-g Accelerometer Part 2 - Accelerometer Products and Applications Source: Freescale

2. Introduction Purpose This training module introduces some key products within low-g accelerometers, overview their features and connection with an MCU. Outline Overview of MMA7260Q Overview of MMA73xxL Overview of MMA745xL Contents 18 pages Duration 15 Minutes

3. MMA7260Q: Analog Output Three axes of sensitivity: XYZ Selectable Sensitivity:1.5g / 2g / 4g / 6g Low current consumption: 500 µA Sleep mode: 3 µA Low voltage operation: 2.2V to 3.6V High Sensitivity (800 mV/g @ 1.5g) Fast Turn On Time

4. g-Select Solutions Determine optimal sensitivity The MCU reads the accelerometer output. If a 1.5g setting is railed for 2 ms then the MCU can adjust the g-range to 2g and sample data again. Run multiple accelerometer applications The MCU can toggle between a freefall detection algorithm with a 1.5g setting and a vibration algorithm at the 6g setting .

5. MMA7260Q Basic Connection with an MCU

6. MMA73xxL: Analog Output Features 3-axis analog output with g-select MMA736xL: 1.5g, 6g MMA7341L: 3g, 11g MMA733xL: 4g, 12g Low current consumption: 400 µA Sleep mode: 3 µA Low voltage operation: 2.2V to 3.6V 0g-Detect for freefall protection Self test for freefall function check

7. MMA73xxL Basic Connection with an MCU

8. MMA745xL: Digital Output Features I 2 C or SPI digital output Selectable sensitivity: 2g / 4g / 8g Low voltage operation: 2.4V to 3.6V Self test for Z-axis Low current consumption: 400 µA Sleep mode: 5 µA Programmable threshold interrupt output Free fall interrupt output Low external component count

9. Connecting MMA745xL to an MCU using I 2 C I 2 C Connectivity I 2 C SCL and SDA 2 Interrupts

10. Connecting MMA745xL to an MCU using SPI SPI Connectivity SPI SCK, MISO, MOSI, CS 2 Interrupts

11. Basic Start-up Procedure for MMA745xL Set-up the microcontroller hardware for SPI or I 2 C communication. Configure the clock speed and all the pins required Write simple single byte Read and Write command to communicate to the device. Write to the MMA745xL Register $16, sending in a value of 0x05 to set up the device for measurement mode with ±2g dynamic range. Read the Control Register $16 to ensure that the value is correct (0x05). Read the X, Y and Z registers and watch the outputs change.

12. Design Support Evaluation board Demo board Software available Connectors CD-ROM

13. KIT3468MMA745xL: Accelerometer Evaluation Board The accelerometer with all pins mapped out to a 14 pin header

14. ZSTAR3 Development Tool Multiple wireless sensing triple-axis reference design Sensing acceleration in 3-axes Support for digital and analog sensors Wireless communication with sensors through the 2.4 GHz band RF protocol supports 16 sensors on one USB stick (receiver) Configurable Sensor Data rate of 30, 60 or 120 Hz Virtual serial port - interface for GUI and serial port terminal Current consumption: In normal run mode: 1.8 - 3.9 mA, depending on the actual data rate In sleep mode: less than 900 nA Smart Power consumption: power cycling is dependent on the sensor's motion detection. At a standstill, the board transmits only every 10th packet

15. Sensor Placement The MEMS sensor is very sensitive to stress. Not place the sensor near an edge where it may be knocked around or touched by people’s hands. Avoid bending the PCB as the PCB stress is transferred to the accelerometer. Avoid placing the sensor close to components that may have large temperature variations or that are constantly very hot. Place the sensor away from the center of the device

16. Human Fall Detection System A person's fall is usually an indicator of an emergency, especially in some groups (elderly people, firemen, policemen). Requirements of the system Small Battery powered Good accuracy

17. Hardware Architecture

18. Additional Resource For ordering the low-g accelerators, please click the part list or Call our sales hotline For additional inquires contact our technical service hotline For more product information go to http://www.freescale.com/webapp/sps/site/taxonomy.jsp?nodeId=01126911184209 Newark Farnell