Freescale MMA7455L User Manual

Freescale Semiconductor

123456

7

8 9 10 11 12 13

14

AVDD

GND

DVDD_IO

SCL/SPCCS

INT1/DRDY

INT2

N/C

SDO

SDA/SDI/SDO

N/C

IADDR0

N/C

GND

Technical Data

±2g/±4g/±8g Three Axis Low-g

Document Number: MMA7455L

Rev 4, 08/2008

Digital Output Accelerometer

The MMA7455L is a Digital Output (I2C/SPI), low power, low profile
capacitive micromachined accelerometer featuring signal conditioning, a low
pass filter, temperature compensation, self-test, configurable to detect 0g
through interrupt pins (INT1 or INT2), and pulse detect for quick motion
detection. 0g offset and sensitivity are factory set and require no external
devices. The 0g offset can be customer calibrated using assigned 0g registers
and g-Select which allows for command selection for 3 acceleration ranges
(2g/4g/8g). The MMA7455L includes a Standby Mode that makes it ideal for
handheld battery powered electronics.

Features

2

• Digital Output (I

• 3mm x 5mm x 1mm LGA-14 Package

• Low Current Consumption

• Self-Test for Z-Axis

• Low Voltage Operation: 2.4 V – 3.6 V

• User Assigned Registers for Offset Calibration

• Programmable Threshold Interrupt Output

• Level Detection for Motion Recognition (Shock, Vibration, Freefall)

• Pulse Detection for Single or Double Pulse Recognition

• Sensitivity (64 LSB/g @ 2g and @ 8g in 10-Bit Mode)

• Selectable Sensitivity (±2g, ±4g, ±8g) for 8-bit Mode

• Robust Design, High Shocks Survivability (5,000g)

• RoHS Compliant

• Environmentally Preferred Product

• Low Cost

C/SPI)

MMA7455L

MMA7455L: XYZ-AXIS

ACCELEROMETER

±2G/±4G/±8G

Bottom View

14 LEAD

LGA

CASE 1977-01

Top View

Typical Applications

• Cell Phone/PMP/PDA: Image Stability, Text Scroll, Motion Dialing, Tap to

Mute

• HDD: Freefall Detection

• Laptop PC: Freefall Detection, Anti-Theft

• Pedometer

• Motion Sensing, Event Recorder

ORDERING INFORMATION

Part Number Temperature Range Package Shipping

MMA7455LT

MMA7455LR1

MMA7455LR2

This document contains certain information on a new product.
Specifications and information herein are subject to change without notice.

© Freescale Semiconductor, Inc., 2007, 2008. All rights reserved.

–40 to +85°C LGA-14 Tray

–40 to +85°C LGA-14 7” Tape & Reel

–40 to +85°C LGA-14 13” Tape & Reel

Figure 1. Pin Connections

Contents

ELECTRO STATIC DISCHARGE (ESD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

PRINCIPLE OF OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

FEATURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

Self-Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

g-Select . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

Standby Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

Measurement Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

LEVEL DETECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

$18: Control 1 (Read/Write) Setting the Detection Axes for X, Y and Z . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

$19: Control 2 (Read/Write) Motion Detection (OR Condition) or Freefall Detection (AND Condition) . . . . . . . . . . . .10

$18: Control 1 (Read/Write): Setting the threshold to be an integer value or an absolute value . . . . . . . . . . . . . . . . .10

$1A: Level Detection Threshold Limit Value (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

THRESHOLD DETECTION FOR MOTION AND FREEFALL CONDITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

CASE 1: Motion Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

CASE 2: Motion Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

CASE 3: Freefall Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

CASE 4: Freefall Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

PULSE DETECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

$18: Control 1 (Read/Write): Disable X, Y or Z for pulse detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

$19: Control 2 (Read/Write): Motion Detection (OR condition) or Freefall Detection (AND condition) . . . . . . . . . . . . .12

CASE 1: Single Pulse Motion Detection: X or Y or Z > Pulse Threshold for Time < Pulse Duration . . . . . . . . . . . . . .12

CASE 2: Freefall Detection: X and Y and Z < Pulse Threshold for Time > Latency Time . . . . . . . . . . . . . . . . . . . . . .13

CASE 3: Double Pulse Detection: X OR Y OR Z > Threshold for Pulse Duration1 < PDTime1, Latency Time, AND .14

ASSIGNING, CLEARING & DETECTING INTERRUPTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

Clearing the Interrupt Pins: Register $17 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

Detecting Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

DIGITAL INTERFACE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

BASIC CONNECTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

REGISTER DEFINITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

SOLDERING AND MOUNTING GUIDELINES FOR THE LGA ACCELEROMETER SENSOR TO A PC BOARD . . . . . . . . . .29

2

C Slave Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

I

SPI Slave Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

Pin Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

Recommended PCB Layout for Interfacing Accelerometer to Microcontroller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

MMA7455L

Sensors

2 Freescale Semiconductor

List of Figures

Pin Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Simplified Accelerometer Functional Block Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

Simplified Transducer Physical Model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Single Pulse Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Freefall Detection in Pulse Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Double Pulse Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Single Byte Read - The Master is reading one address from the MMA7455L . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Multiple Bytes Read - The Master is reading multiple sequential registers from the MMA7455L . . . . . . . . . . . . . . . . . . . . . . . . 17

Single Byte Write - The Master (MCU) is writing to a single register of the MMA7455L . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Multiple Byte Writes - The Master (MCU) is writing to multiple sequential registers of the MMA7455L . . . . . . . . . . . . . . . . . . . 17

SPI Timing Diagram for 8-Bit Register Read (4 Wire Mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

SPI Timing Diagram for 8-Bit Register Read (3 Wire Mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

SPI timing Diagram for 8-Bit Register Write (3 Wire Mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Pinout Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2

C Connection to MCU. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

I

SPI Connection to MCU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Sensing Direction and Output Response at 2g Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Recommended PCB Land Pattern for the 5 x 3 mm LGA Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Incorrect PCB Top Metal Pattern Under

Package. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Correct PCB Top Metal Pattern Under Package. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

Recommended PCB Land Pad, Solder Mask, and Signal Trace Near Package Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

Stencil Design Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

MMA7455L

Sensors
Freescale Semiconductor 3

List of Tables

Pin Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

Maximum Ratings

(Maximum ratings are the limits to which the device can be exposed without causing permanent damage.) . . . . . . . . . . . . . . .6

Operating Characteristics

Unless otherwise noted: –40°C < TA < 85°C, 2.4 V < AVDD < 3.6 V, Acceleration = 0g, Loaded output. . . . . . . . . . . . . . . . . . .7

Function Parameters for Detection

–40°C < TA < 85°C, 2.4 V < AVDD < 3.6 V, unless otherwise specified . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

$16: Mode Control Register (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

Configuring the g-Select for 8-bit output using Register $16 with GLVL[1:0] bits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

Configuring the Mode using Register $16 with MODE[1:0] bits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

THOPT = 0 Absolute; THOPT = 1 Positive Negative . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

$1B: Pulse Detection Threshold Limit Value (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

$1C: Pulse Duration Value (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

$1B: Pulse Detection Threshold Limit Value (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

$1D: Latency Time Value (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

$1B: Pulse Detection Threshold Limit Value (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

$1C: Pulse Duration Value (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

$1D: Latency Time Value (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

$1E: Time Window for 2nd Pulse Value (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

$18 Control 1 Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

Configuring the Interrupt settings using Register $18 with INTREG[1:0] bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

$17: Interrupt Latch Reset (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

$0A: Detection Source Register (Read only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

Pin Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

User Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

$00: 10bits Output Value X LSB (Read only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

$01: 10bits Output Value X MSB (Read only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

$02: 10bits Output Value Y LSB (Read only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

$03: 10bits Output Value Y MSB (Read only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

$05: 10bits Output Value X MSB (Read only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

$06: 8bits Output Value X (Read only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

$07: 8bits Output Value Y (Read only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

$08: 8bits Output Value Z (Read only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

$09: Status Register (Read only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

$0A: Detection Source Register (Read only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

$0D: I2C Device Address (Bit 6-0: Read only, Bit 7: Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

$0E: User Information (Read Only: Optional) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

$0F: “Who Am I” Value (Read only: Optional) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

$10: Offset Drift X LSB (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

$11: Offset Drift X MSB (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

$12: Offset Drift Y LSB (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

$13: Offset Drift Y MSB (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

$14: Offset Drift Z LSB (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

$15: Offset Drift Z MSB (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

$16: Mode Control Register (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

Configuring the g-Select for 8-bit output using Register $16 with GLVL[1:0] bits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

$17: Interrupt Latch Reset (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26

$18 Control 1 (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26

Configuring the Interrupt settings using Register $18 with INTREG[1:0] bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26

$1A: Level Detection Threshold Limit Value (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

$1B: Pulse Detection Threshold Limit Value (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

$1C: Pulse Duration Value (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

$1D: Latency Time Value (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

$1E: Time Window for 2nd Pulse Value (Read/Write) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

Acceleration vs. Output (8-bit data) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

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Table 1. Pin Descriptions

Pin # Pin Name Description Pin Status

1 DVDD_IO Digital Power for I/O pads Input

2 GND Ground Input

3 N/C No internal connection. Leave unconnected or connect to Ground. Input

4 IADDR0

2

C Address Bit 0 (optional)*

I

5 GND Ground Input

6 AVDD Analog Power Input

7CS

SPI Enable (0), I

2

C Enable (1)

8 INT1/DRDY Interrupt 1/ Data Ready Output

9 INT2 Interrupt 2 Output

10 N/C No internal connection. Leave unconnected or connect to Ground. Input

11 N/C Leave unconnected or connect to Ground. Input

12 SDO SPI Serial Data Output Output

13 SDA/SDI/SDO

14 SCL/SPC

2

C Serial Data (SDA), SPI Serial Data Input (SDI), 3-wire interface Serial Data Output (SDO)

I

2

C Serial Clock (SCL), SPI Serial Clock (SPC)

I

Open Drain/Input/Output

*This address selection capability is not enabled at the default state. If the user wants to use it, factory programming is required. If activated (pin4
on the device is active).

<$1D= 0001 1101> bit 0 is V

on pin 4

DD

<$1C=0001 1100> bit 0 is GND on pin 4. If the pin is programmed it cannot be left NC.

Input

Input

Input

Figure 1. Simplified Accelerometer Functional Block Diagram

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Freescale Semiconductor 5

Table 2. Maximum Ratings

(Maximum ratings are the limits to which the device can be exposed without causing permanent damage.)

Rating Symbol Value Unit

Maximum Acceleration (all axes) g

Analog Supply Voltage AV

Digital I/O pins Supply Voltage DV

Drop Test D

Storage Temperature Range T

max

DD

DD_IO

drop

stg

5000 g

-0.3 to +3.6 V

-0.3 to +3.6 V

1.8 m

-40 to +125 °C

ELECTRO STATIC DISCHARGE (ESD)

WARNING: This device is sensitive to electrostatic discharge.

Although the Freescale accelerometer contains internal 2000V ESD protection circuitry, extra precaution must be taken by the
user to protect the chip from ESD. A charge of over 2000 volts can accumulate on the human body or associated test equipment.
A charge of this magnitude can alter the performance or cause failure of the chip. When handling the accelerometer, proper ESD
precautions should be followed to avoid exposing the device to discharges which may be detrimental to its performance.

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6 Freescale Semiconductor

Table 3. Operating Characteristics

Unless otherwise noted: –40°C <

Analog Supply Voltage

Standby/Operation Mode

Enable Bus Mode

Digital I/O Pins Supply Voltage

Standby/Operation Mode

Enable Bus Mode

Supply Current Drain

Operation Mode

Pulse Detect Function Mode

Standby Mode (except data loading and I

Operating Temperature Range T

0g Output Signal (T

±2g range (25°C) 8bit GLVL[1:0]= 0 1
±4g range (25°C) 8bit GLVL[1:0]= 1 0
±8g range (25°C) 8bit GLVL[1:0]= 0 0
±8g range (25°C) 10bit

Sensitivity (T

±2g range (25°C) 8bit
±4g range (25°C) 8bit
±8g range (25°C) 8bit
±8g range (25°C) 10bit

Self-Test Output Response

Zout ΔST

Input High Voltage
Input Low Voltage

Internal Clock Frequency (T

SPI Frequency

DD_IO

DD_IO

< 2.4 V
> 2.4 V

DV

DV

Bandwidth for Data Measurement (User Selectable)

DFBW 0

DFBW 1

Output Data Rate

Output Data Rate is 125 Hz when 62.5 bandwidth is selected.

Output Data rate is 250 Hz when 125Hz bandwidth is selected.

Control Timing

Wait Time for I

Turn On Response Time (Standby to Normal Mode)

Turn Off Response Time (Normal to Standby Mode)

Self-Test Response Time

Sensing Element Resonant Frequency

XY
Z

Nonlinearity (2 g range) -1 — +1 %FS

Cross Axis Sensitivity -5 — +5 %

=25°C, AVDD = 2.8 V

A

=25°C, AV

A

2

DD

C/SPI ready after power on

TA < 85°C, 2.4 V < AVDD < 3.6 V, Acceleration = 0g, Loaded output.

Characteristic Symbol Min Typ Max Unit

2

C/SPI communication period)

= 2.8 V)

= 25°C, AVDD = 2.8 V) t

A

AV

DD

AV

DD

DV

DD_IO

DV

DD_IO

I

DD

I

DD

I

DD

A

V

IH

V

IL

CLK

t

su

t

ru

t

rd

t

st

f

GCELLXY

f

GCELLZ

Z

2.4

2.8

3.6

0

1.71

1.71

—
—
—

1.8

1.8

400
400

2.5

AV

DD

3.6

490
490

10

-40 25 85 °C

-21
—
—

-21

58
—
—
58

64
32
16
64

0
0
0
0

21
—
—
21

70
—
—
70

+48 +64 +80 count

0.7 x DVDD
—

—
—

—

0.35 x DVDD

140 150 160 kHz

—
—

—
—

—
—

—
—
—
—

—
—

4
8

62.5
125

125
250

1
—
—
—

6.0

3.4

—
—

—
—

—
—

—
20
20
20

—
—

count/g
count/g
count/g
count/g

V
V

V
V

μA
μA
μA

count
count
count
count

V
V

MHz
MHz

Hz
Hz

Hz
Hz

ms
ms
ms
ms

kHz
kHz

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Table 4. Function Parameters for Detection

–40°C <

Note: The response time is between 10% of full scale VDD input voltage and 90% of the final operating output voltage.
*The bandwidth for detecting interrupts in level and pulse is 600Hz which is changed from measurement mode.

TA < 85°C, 2.4 V < AVDD < 3.6 V, unless otherwise specified

Characteristic Symbol Min Typ Max Unit

Level Detection

Detection Threshold Range 0 — FS g

Pulse Detection

Pulse detection range (Adjustable range)
Time step for pulse detection
Threshold range for pulses
Detection levels for threshold
Latency timer (Adjustable range)
Time Window (Adjustable range)
Bandwidth for detecting interrupt*
Time step for latency timer and time window

0.5
—

0

—

1

1
—
—

—

0.5
—

127

—
—

600

1

127

—

FS

—
150
250

—

—

ms
ms

g

Counts

ms
ms
Hz
ms

PRINCIPLE OF OPERATION

The Freescale accelerometer is a surface-micromachined integrated-circuit accelerometer. The device consists of a surface mi­cromachined capacitive sensing cell (g-cell) and a signal conditioning ASIC contained in a single package. The sensing element
is sealed hermetically at the wafer level using a bulk micromachined cap wafer. The g-cell is a mechanical structure formed from
semiconductor materials (polysilicon) using semiconductor processes (masking and etching). It can be modeled as a set of
beams attached to a movable central mass that move between fixed beams. The movable beams can be deflected from their
rest position by subjecting the system to an acceleration (Figure 2).

As the beams attached to the central mass move, the distance from them to the fixed beams on one side will increase by the
same amount that the distance to the fixed beams on the other side decreases. The change in distance is a measure of accel­eration. The g-cell beams form two back-to-back capacitors (Figure 2). As the center beam moves with acceleration, the distance
between the beams changes and each capacitor's value will change, (C = A
electric constant, and D is the distance between the beams.

The ASIC uses switched capacitor techniques to measure the g-cell capacitors and extract the acceleration data from the differ­ence between the two capacitors. The ASIC also signal conditions and filters (switched capacitor) the signal, providing a digital
output that is proportional to acceleration.

ε/D). Where A is the area of the beam, ε is the di-

Acceleration

Figure 2. Simplified Transducer Physical Model

FEATURES

Self-Test

The sensor provides a self-test feature that allows the verification of the mechanical and electrical integrity of the accelerometer
at any time before or after installation. This feature is critical in applications such as hard disk drive protection where system in­tegrity must be ensured over the life of the product. When the self-test function is initiated through the mode control register ($16),
accessing the “self-test” bit, an electrostatic force is applied to each axis to cause it to deflect. The Z-axis is trimmed to deflect
1g. This procedure assures that both the mechanical (g-cell) and electronic sections of the accelerometer are functioning.

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g-Select

The g-Select feature enables the selection between 3 acceleration ranges for measurement. Depending on the values in the
Mode control register ($16), the MMA7455L’s internal gain will be changed allowing it to function with a 2g, 4g or 8g measurement
sensitivity. This feature is ideal when a product has applications requiring two or more acceleration ranges for optimum perfor­mance and for enabling multiple functions. The sensitivity can be changed during the operation by modifying the two GLVL bits
located in the mode control register.

$16: Mode Control Register (Read/Write)

D7 D6 D5 D4 D3 D2 D1 D0 Bit

-- DRPD SPI3W STON GLVL[1] GLVL[0] MODE[1] MODE[0] Function

0 0 0 0 0 0 0 0 Default

Table 5. Configuring the g-Select for 8-bit output using Register $16 with GLVL[1:0] bits.

GLVL [1:0] g-Range Sensitivity

00 8g 16 LSB/g

01 2g 64 LSB/g

10 4g 32 LSB/g

Standby Mode

This digital output 3-axis accelerometer provides a standby mode that is ideal for battery operated products. When standby mode
is active, the device outputs are turned off, providing significant reduction of operating current. When the device is in standby
mode the current will be reduced to 2.5 µA typical. In standby mode the device can read and write to the registers with the I

2

C/
SPI available, but no new measurements can be taken in this mode as all current consuming parts are off. The mode of the device
is controlled through the mode control register by accessing the two mode bits as shown in Table 6.

Table 6. Configuring the Mode using Register $16 with MODE[1:0] bits.

MODE [1:0] Function

00 Standby Mode

01 Measurement Mode

10 Level Detection Mode

11 Pulse Detection Mode

Measurement Mode

During measurement mode, continuous measurements on all three axes enabled. The g-range for 2g, 4g, or 8g are selectable
with 8-bit data and the g-range of 8g is selectable with 10-bit data. The sample rate during measurement mode is 125 Hz with

62.5 BW filter selected. The sample rate is 250 Hz with the 125 Hz filter selected. Therefore, when a conversion is complete
(signaled by the DRDY flag), the next measurement will be ready.

When measurements on all three axes are completed, a logic high level is output to the DRDY pin, indicating “measurement data
is ready.” The DRDY status can be monitored by the DRDY bit in Status Register (Address: $09). The DRDY pin is kept high until
one of the three Output Value Registers are read. If the next measurement data is written before the previous data is read, the
DOVR bit in the Status Register will be set. Also note that in measurement mode, level detection mode and pulse detection mode
are not available.

By default all three axes are enabled. X and/or Y and/or Z can be disabled. There is a choice between detecting an absolute
signal or a positive or negative only signal on the enabled axes. There is also a choice between doing a detection for motion
where X or Y or Z > Threshold vs. doing a detection for freefall where X & Y & Z < Threshold.

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LEVEL DETECTION

When in Level or Pulse detection mode, it is not advisable to read the XYZ measurements because this can conflict with timing.
The interrupts for level and pulse detection are at 600 Hz, while measurement mode is at 125 Hz. It is best to exit the pulse/level
mode before taking a measurement on the XYZ.

Both the Level Detection and Pulse Detection modes can trigger an interrupt. Typically one interrupt is assigned to either pulse
detection or level detection. To detect both at the same time 2 interrupts are required. The level detection mechanism has no
timers associated with it. Once a set acceleration level is reached the interrupt pin will go high and remain high until the interrupt
pin is cleared (See Assigning, Clearing & Detecting Interrupts).

By default all three axes are enabled and the detection range is 8g only. X and/or Y and/or Z can be disabled. There is a choice
between detecting an Absolute signal or a Positive or Negative only signal on the enabled axes. There is also a choice between
doing a detection for Motion where X or Y or Z > Threshold vs. doing a detection for Freefall where X& Y & Z < Threshold.

$18: Control 1 (Read/Write) Setting the Detection Axes for X, Y and Z

This allows the user to define how many axes to use for detection. All axes are enabled by default. To disable write 1.

XDA: Disable X

YDA: Disable Y

ZDA: Disable Z

D7 D6 D5 D4 D3 D2 D1 D0 Reg $18

DFBW THOPT ZDA YDA XDA INTREG[1] INTREG[0] INTPIN Function

00000000Default

$19: Control 2 (Read/Write) Motion Detection (OR Condition) or Freefall Detection (AND Condition

)

LDPL = 0: Level detection polarity is positive and detecting condition is OR for all 3 axes.

X or Y or Z > Threshold
||X|| or ||Y|| or ||Z|| > Threshold
LDPL = 1: Level detection polarity is negative detecting condition is AND for all 3 axes.
X and Y and Z < Threshold
||X|| and ||Y|| and ||Z|| < Threshold

D7 D6 D5 D4 D3 D2 D1 D0 Reg $19

-- -- -- -- -- DRVO PDPL LDPL Function
00000000Default

$18: Control 1 (Read/Write): Setting the threshold to be an integer value or an absolute value

This allows the user to set the threshold to be absolute, or to be based on the threshold value as positive or negative.

THOPT = 0 Absolute; THOPT = 1 Positive Negative

D7 D6 D5 D4 D3 D2 D1 D0 Reg $18

DFBW THOPT ZDA YDA XDA INTREG[1] INTREG[0] INTPIN Function

00000000Default

$1A: Level Detection Threshold Limit Value (Read/Write)

When an event is detected the interrupt pin (either INT1 or INT2) will go high. The interrupt pin assignment is set up in Register
$18, discussed in the Assigning, Clearing & Detecting Interrupts section. The detection status is monitored by the Detection
Source Register $0A.

D7 D6 D5 D4 D3 D2 D1 D0 Reg $1A

LDTH[7] LDTH[6] LDTH[5] LDTH[4] LDTH[3] LDTH[2] LDTH[1] LDTH[0] Function

00000000Default

LDTH[7:0]: Level detection threshold value. If THOPT bit in Detection Control Register is “0”, it is unsigned 7 bits value and
LDTH[7] should be “0”. If THOPT bit is “1”, it is signed 8 bits value.

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THRESHOLD DETECTION FOR MOTION AND FREEFALL CONDITIONS

CASE 1: Motion Detection

Integer Value: X >Threshold OR Y >Threshold OR Z > Threshold

Reg $18 THOPT=1; Reg 19 LDPL=0, Set Threshold to 3g, which is 47 counts (16 counts/g). Set register $1A LDTH = $2F.

TH = $2F

CASE 2: Motion Detection

Absolute: ||X|| > Threshold OR ||Y|| >Threshold OR ||Z|| > Threshold

Reg $18 THOPT=0; Reg 19 LDPL=0, Set Threshold to 3g, which is 47 counts (16 counts/g). Set register $1A LDTH = $2F.

TH = $2F

TH = $D1

CASE 3: Freefall Detection

Integer Value: X < Threshold AND Y < Threshold AND Z <Threshold

Reg $18 THOPT=1; Reg 19 LDPL=1, Set Threshold to 0.5g, which is 7 counts (16 counts/g). Set register $1A LDTH = $07

TH = $07

CASE 4: Freefall Detection

Absolute: ||X|| <Threshold AND ||Y|| < Threshold AND ||Z||< Threshold

Reg $18 THOPT=0; Reg 19 LDPL=1, Set Threshold to +/-0.5g, which is 7 counts (16 counts/g). Set register $1A LDTH = $07.

TH = $07

TH = $F9

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