MMA7455LR2 - Freescale Semiconductor

Document Number: MMA7455L

Rev 10, 12/2009

Freescale Semiconductor

Technical Data

This document contains certain information on a new product.

Specifications and information herein are subject to change without notice.

±2g/±4g/±8g Three Axis Low-g

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

• Digital Output (I2C/SPI)

• 3mm x 5mm x 1mm LGA-14 Package

• 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 Reco gnition

• 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

Typical Applications

• Cell Phone/PMP/PDA: Image Stability, Text Scroll, Motion Dialin g,

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 –40 to +85°C LGA-14 Tray

MMA7455LR1 –40 to +85°C LGA-14 7” Tape & Reel

MMA7455LR2 –40 to +85°C LGA-14 13” Tape & Reel

MMA7455L

MMA7455L: XYZ-AXIS

ACCELEROMETER

±2g/±4g/±8g

14 LEAD

LGA

CASE 1977-01

Bottom View

Figure 1. Pin Connectio ns

Top View

8913

10 11

165432

AVDD

GND

DVDD_IO

SCL/SPCCS

INT1/DRDY

INT2

N/C

SDO

SDA/SDI/SDO

N/C

IADDR0 N/C

GND

Sensors

Freescale Semiconductor 2

MMA7455L

Contents

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

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

FEATURES ..................................................................................................................................................................................9

Self-Test .........................................................................................................................................................................9

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 Conditio n) or Freefall Detection (AND Condition) ........................10

$18: Control 1 (Read/Write): Setting the th reshold 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, .........14

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

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

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

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

I2C Slave Interface ........................................... .. ... .............. ... ... .............. ... .. .............. ... ... ............................................16

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

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

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

Recommended PCB Layout for Interfa c ing Accelerometer to Microcontroller .............................................................19

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

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

Sensors

Freescale Semiconductor 3

MMA7455L

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 writi ng 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

I2C Connection to MCU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

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, Solde r Mask, and Signal Tra ce Near Pa ckage Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

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

Temperature Coefficient of Offset (TCO) and Temperature Coefficient of Sensitivity (TCS) Distribution Charts . . . . . . . . . . .32

MMA7455L Current Distribution Charts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

Sensors

Freescale Semiconductor 4

MMA7455L

List of Tables

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

Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Operating Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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 Inte rrupt 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) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

$0E: User Information (Read Only: Optional) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

$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) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

$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

Configuring the Mode using Register $16 with MODE[1:0] bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

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

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

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

$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

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

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

Sensors

Freescale Semiconductor 5

MMA7455L

Table 1. Pin Descriptions

*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 VDD on pin 4

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

Figure 2. Simplified Accelerometer Functional Block Diagram

Pin # Pin Name Description Pin Status

1 DVDD_IO Digital Power for I/O pads Input

2GND

Ground Input

3N/C

No internal connection. Leave unconnected or connect to Ground. Input

4 IADDR0 I2C Address Bit 0 (optional)* Input

5GND

Ground Input

6 AVDD Analog Power Input

7CS

SPI Enable (0), I2C Enable (1) Input

8 INT1/DRDY Interrupt 1/ Data Ready Output

9INT2

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 I2C Serial Data (SDA), SPI Serial Data Input (SDI), 3-wire interface Serial Data Output (SDO) Open Drain/Input/Output

14 SCL/SPC I2C Serial Clock (SCL), SPI Serial Clock (SPC) Input

Sensors

6Freescale Semiconductor

MMA7455L

ELECTRO STAT IC DISC HARGE (ESD)

WARNING: This device is se ns itive to electrostatic disch ar ge .

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.

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) gmax 5000 g

Analog Supply Voltage AVDD -0.3 to +3.6 V

Digital I/O pins Supply Voltage DVDD_IO -0.3 to +3.6 V

Drop Test Ddrop 1.8 m

Storage Temperature Range Tstg -40 to +125 °C

Sensors

Freescale Semiconductor 7

MMA7455L

Table 3. Operating Characteristics

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

Characteristic Symbol Min Typ Max Unit

Analog Supply Voltage

Standby/Operation Mode

Enable Bus Mode

Digital I/O Pins Supply Voltage(1)

Standby/Operation Mode

Enable Bus Mode

AVDD

DVDD_IO

2.4

2.8

3.6

Supply Current Drain

Operation Mode

Pulse Detect Function Mode

Standby Mode (except data loading and I2C/SPI communication period)

IDD

—

400

2.5

490

μA

Operating Temperature Range TA-40 25 85 °C

0g Output Signal (TA=25°C, AVDD = 2.8 V)

±2g range (25°C) 8-bit GLVL[1:0]= 0 1

±4g range (25°C) 8-bit GLVL[1:0]= 1 0

±8g range (25°C) 8-bit GLVL[1:0]= 0 0

±8g range (25°C) 10-bit

-18

-10

-5

-18

count

Sensitivity (TA=25°C, AVDD = 2.8 V)

±2g range (25°C) 8-bit

±4g range (25°C) 8-bit

±8g range (25°C) 8-bit

±8g range (25°C) 10-bit

14.5

17.5

count/g

Self-Test Output Response

Zout ΔSTZ32 64 83 count

Temperature Compensation for Offset TCO ±3.5 ±0.5 +3.5 mg/°C

Temperature Sensitivity for Offset TCS ±0.026 ±0.01 +0.026 mg/°C

Input High Voltage

Input Low Voltage VIH

VIL

0.7 x DVDD

——

0.35 x DVDD V

Internal Clock Frequency (TA = 25°C, AVDD = 2.8 V) tCLK 140 150 160 kHz

SPI Frequency

DVDD_IO < 2.4 V

DVDD_IO > 2.4 V —

—4

8—

—MHz

MHz

Bandwidth for Data Measurement (User Selectable)

DFBW 0

DFBW 1 —

—62.5

125 —

—Hz

Output Data Rate

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

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

—125

250 —

—Hz

Control Timing

Wait Time for I2C/SPI ready after power on

Turn On Response Time (Standby to Normal Mode)

Turn Off Response Time (Normal to Standby Mode)

Self-Test Response Time

Sensing Element Resonant Frequency

tsu

tru

trd

tst

fGCELLXY

fGCELLZ

—

6.0

3.4

—

kHz

Nonlinearity (2 g range) -1 — +1 %FS

Cross Axis Sensitivity -5 — +5 %

1. It is recommended to tie the analog and digital supply voltages together.

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8Freescale Semiconductor

MMA7455L

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.

PRINCIPLE OF OPERATION

The Freescale accelerometer is a surface-micromachined integrated-circuit accelerometer. The device consists of a surface mi-

cromachined 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 (po lysilicon) 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 3).

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 accel-

eration. The g-cell beams form two back-to-back capacitors (Figure 3). As the center beam moves with acceleration, the distance

between the beams changes and each capacitor's value will change, (C = Aε/D). Where A is the area of the beam, ε is the di-

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 differ-

ence between the two capacitors. The ASIC also signal conditions and filters (switched capacitor) the signal, providing a digital

output that is proportional to acceleration.

Figure 3. Sim plified Tran sducer Physical Model

Table 4. Function Parameters for Detection

–40°C < 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 interrup t *

Time step for latency timer and time window

0.5

—

0.5

—

127

—

600

127

—

150

250

—

Counts

Acceleration

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Freescale Semiconductor 9

MMA7455L

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 in-

tegrity 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.

g-Select

The g-Select feature enables the selection between 3 acceleration rang es 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 applica tions requiring two or more acceleration ranges for optimum perfor-

mance 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.

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 I2C/

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.

Measurement Mode

The device can read XYZ measurements in this mode. The pulse and threshold interrupts are not active. 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 st atus can be monitored by the DRDY bit in St atus 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 avai lable.

By default all three axes are enabled . X and/or Y and/or Z can be disable d. There is a choi ce between detecting an absolute

signal or a positive or negative only signal on the enabled axes. There is also a choice between doing a dete ction for motion

where X or Y or Z > Threshold vs. doing a detection for freefall where X & Y & Z < Threshold.

$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

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

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10 Freescale Semiconductor

MMA7455L

LEVEL DETECTION

The user can access XYZ measurements and can use the level interrupt only. The level detection mechanism has no timers as-

sociated 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

$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 cond ition is AND for all 3 axes.

X and Y and Z < Threshold

||X|| and ||Y|| and ||Z|| < Threshold

$18: Control 1 (Read/Write): Setting the threshold to be an intege r 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

$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.

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.

D7 D6 D5 D4 D3 D2 D1 D0 Reg $18

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

00000000Default

D7 D6 D5 D4 D3 D2 D1 D0 Reg $19

-- -- -- -- -- DRVO PDPL LDPL Function

00000000Default

D7 D6 D5 D4 D3 D2 D1 D0 Reg $18

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

00000000Default

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

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Freescale Semiconductor 11

MMA7455L

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.

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.

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

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, whi c h is 7 counts (16 counts/g). Set register $1A LDTH = $07.

TH = $2F

TH = $D1

TH = $07

TH = $F9

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12 Freescale Semiconductor

MMA7455L

PULSE DETECTION

In Pulse Mode, all functions can be active including measurements, level detections and pulse detection. There are two interrupt

pins available for detection of level and pulse conditions. The pulse detection has several timing windows associated with it. A

single pulse and a double pulse can be detected. Also freefall can be detected. The interrupt pins can be assigned to detect the

first pulse on one interrupt and the second pulse on the other interrupt. This is explained on Page 15, under the Assigning, Clear-

ing & Detecting Interrupts section.

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 doing a detectio n for Motion detection vs. doing a detection for Freefall.

$18: Control 1 (Read/Write): Disable X, Y or Z for Pulse Detection

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.

$19: Control 2 (Read/Write): Motion Detection (OR conditio n) or Fr eefall Detection (AND condition)

PDPL

0: Pulse detection polarity is positive and detecting condition is OR 3 axes.

1: Pulse detection polar ity is negative and detecting condition is AND 3 axes.

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

For motion detection with single pulse the device must be in pulse mode. PDPL in Registe r $19 =0 for “OR” motion condition.

The Pulse threshold must be set in Register $1B and the pulse duration time window must also be set using Register $1C. The

pulse must be detected before the time windo w closes for the interrupt to trigger.

D7 D6 D5 D4 D3 D2 D1 D0 Reg $18

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

00000000Default

D7 D6 D5 D4 D3 D2 D1 D0 Reg $19

-- -- -- -- -- DRVO PDPL LDPL Function

00000000Default

$1B: Pulse Detection Threshold Li mit Value (Read/Write)

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

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

00000000Default

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

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

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

00000001Default

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Freescale Semiconductor 13

MMA7455L

Figure 4. Single Pulse Detection

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

For freefall detection, set in pulse mode. PDPL in Register $19 =1 for “AND” freefall condition. The Pulse threshold must be set

in Register $1B and the pulse latency time window must also be set using Register $1D. All three axes must remain below the

threshold longer than the time window for the interrupt to trigger.

Figure 5. Freefall Detection in Pulse Mode

$1B: Pulse Detection Threshold Li mit Value (Read/Write)

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

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

00000000Default

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

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

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

00000001Default

Puls e D etec tion

T ime d uratio n

Gth

INT p in

Time

Single Pulse Detection ($19 PD P L =0 indicating motion detection)

Time Window for 2nd pulse $1E TW=0 indicating single pulse

*Note there is up to

1.6ms de lay on the

interrupt signal

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14 Freescale Semiconductor

MMA7455L

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

X OR Y OR Z > Threshold for Pulse Duration2 < PDTime2

For motion detection with double pulse the device must be in pulse mode. PDPL in Register $19 =0 for “OR” motion condition.

The Pulse Threshold must be set in Register $1B and the Pulse Duration Time Window must also be set using Register $1C.

Then the Latency Time (time between pulses) must be set in Register $1D and then the Second Time Window must be set in

Register $1E for the time window of the second pulse. The pulse must be detected before the time window closes for the interrupt

to trigger.

When any of the events are 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 on Page 15. The detection status is

monitored by the detection source register $0A.

Figure 6. Double Pulse Detecti on

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

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

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

00000000Default

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

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

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

00000001Default

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

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

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

00000001Default

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

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

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

00000000Default

Pulse Detection

Time Window

Gth

D etec tion Source

Latency Time Window

(2nd pulse ignored here)

Puls e Detection Time Window for

2nd pulse

Time

PDX or PDY or PD Z bit in Detect ion

sourc e register is s et.

T ime Window >0 for 2 pulse detec t

INT Time

Time

Double Pulse Detection ($19 PDPL=0 indicating motion detection)

Time Window for 2nd pul se $1E TW>0 indicating double pulse

* Note there is up to 1.6ms

delay on the interrupt signal

* Note there is up to 1.6m s

delay on the interrupt signal

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Freescale Semiconductor 15

MMA7455L

ASSIGNING, CLEARING & DETECTING INTERRUPTS

Assigning the interrupt pins is done in Register $18. There are 3 combinations for the interrupt pins to be assigned which are

outlined below in the table for INTREG[1:0].

Table 7. Configuring the Interrupt settings using Register $18 with INTREG[1:0] bits

00: INT1 Register is detecting Level while INT2 is detecting Pulse.

01: INT1 Register is detecting Pulse while INT2 is detecting Level.

10: INT1 Register is detecting a Single Pulse and INT2 is detecting Single Pulse (if 2nd T ime Window = 0) or if there is a latency

time window and second time window > 0 then INT2 will detect the doubl e pulse only.

INTPIN: INT1 pin is routed to INT1 bit in Detection Source Register ($0A) and INT2 pin is routed to INT2 bit in Detection Source

INTPIN: INT2 pin is routed to INT1 bit in Detection Source Register ($0A) and INT1 pin is routed to INT2 bit in Detection Source

Note: When INTREG[1:0] =10 for the conditi on to detect single pulse on INT1 and either sing le or double pulse on INT2, INT1

register bit can no longer be cleared by setting CLR_INT1 bit. It is cleared by setting CLR_INT2 bit. In this case, setting CLR_INT2

clears both INT1 and INT2 register bits and resets the detection operation. Foll ow the example given for clearing th e interrupts.

Clearing the Interrupt Pins: Register $1 7

CLR_INT1

1: Clear “INT1”

0: Do not clear “INT1”

CLR_INT2

1: Clear “INT2”

0: Do not clear “INT2”

After interrupt has triggered due to a detection, the interrupt pin (INT1 or INT2) need to be cleared by writing a logic 1. Then the

interrupt pin should be enabled to trigger the next detection by setting it to a logic 0.

This example is to show how to reset the interrupt fl ags

void ClearIntLatch(void)

{

IIC_ByteWrite(INTRST, 0x03);

IIC_ByteWrite(INTRST, 0x00);

}

$18 Control 1 Register

D7 D6 D5 D4 D3 D 2 D1 D0 Reg $18

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

00000000Default

INTREG[1:0] “INT1” Register Bit “INT2” Register Bit

00 Level detection Pulse Detection

01 Pulse Detection Level Detection

10 Single Pulse detection Single or Double Pulse Detection

$17: Interrupt Latch Reset (Read/Write)

D7 D6 D5 D4 D3 D 2 D1 D0 Reg $17

-- -- -- -- -- -- CLR_INT2 CLR_INT1 Function

00000000Default

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16 Freescale Semiconductor

MMA7455L

Detecting Interrupts

LDX

1: Level detection event is detected on X-axis

0: Level detection event is not detected on X-axis

LDY

1: Level detection event is detected on Y-axis

0: Level detection event is not detected on Y- axis

LDZ

1: Level detection event is detected on Z-axis

0: Level detection event is not detected on Z-axis

PDX

1: 1st pulse is detected on X-axis

0: 1st pulse is detected on X-axis

PDY

1: 1st pulse is detected on Y-axis

0: 1st pulse is detected on Y-axis

PDZ

1: 1st pulse is detected on Z-axis

0: 1st pulse is detected on Z-axis

INT1

1: Interrupt assigned by INTRG[1:0] bits in Control 1

0: Interrupt assigned by INTRG[1:0] bits in Control 1

INT2

1: Interrupt assigned by INTRG[1:0] bits in Control 1

0: Interrupt assigned by INTRG[1:0] bits in Control 1

DIGITA L INTERFACE

The MMA7455L has both an I2C and SPI digital output available for a communication interface. CS pin is used for selecting the

mode of communication. When CS is low, SPI communication is selected. When CS is high, I2C communication is selected.

Note: It is recommended to disable I2C during SPI communication to avoid communication errors between devices using a dif-

ferent SPI communication protocol. To disable I2C, set the I2CDIS bit in I2C Device Address register using SPI.

I2C Slave Interface

I2C is a synchronous serial communication between a master device and one or more slave devices. The master is typically a

microcontroller, which provides the serial clock signal and addresses the slave device(s) on the bus. The MMA7455L communi-

cates only in slave operation where the device address is $1D. Multiple read and write modes are available. The protocol supports

slave only operation. It does not supp ort Hs mode, “ 10-bit addressing”, “general call” and: ”START byte”.

SINGLE BYTE READ

The MMA7455L has an 10-bit ADC that can sample, convert and return sensor data on request. The transmission of an 8-bit

command begins on the falling edge of SCL. After the eight clock cycles are us ed to send the command, note that the data re-

turned is sent with the MSB first once the data is received. Figure 7 shows the ti ming diagram for the accelerometer 8-bit I2C

read operation. The Master (or MCU) transmits a start condition (ST) to the MMA7455L, slave address ($1D), with the R/W bit

set to “0” for a write, and the MMA7455L sends an acknowledgement. Then the Master (or MCU) transmits the 8-bit address of

the register to read and the MMA7455L sends an acknowledgement. The Master (or MCU) transmits a repeated start condition

(SR) and then addresses the MMA7455L ($1D) with the R/W bit set to “1” for a read from the previously selected register. The

Slave then acknowledges and transmits the data from the requested register. The Master does not acknowledge (NAK) it re-

ceived the transmi tted data, but transmits a stop condition to end the data transfer.

MULTIPLE BYTES READ

The MMA7455L automatically increments the received register address commands after a read command is received. Therefore,

after following the steps of a single byte read, multiple bytes of data can be read from sequential registers after each MMA7455L

acknowledgment (AK) is received until a NACK is received from the Master followed by a stop condition (SP) signalling an end

of transmission. See Figure 8.

$0A: Detection Source Register (Read only)

D7 D6 D5 D4 D3 D2 D1 D0 Reg $0A

LDX LDY LDZ PDX PDY PDZ INT2 INT1 Function

00000000Default

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Freescale Semiconductor 17

MMA7455L

SINGLE BYTE WRITE

To start a write command, the Master transmits a start condition (ST) to the MMA7455L, slave address ($1D) with the R/W bit set

to “0” for a write, the MMA7455L sends an acknowledgement. Then the Master (MCU) transmits the 8-bit address of the register

to write to, and the MMA7455L sends an acknowledgement. Th en the Master (or MCU) transmits the 8-bit data to write to the

designated register and the MMA7455L sends an acknowledgement that it has received the data. Since this transmission is com-

plete, the Master transmits a stop condition (SP) to the data transfer. The data sent to the MMA7455L is now stored in the ap-

propriate register. See Figure 9.

Figure 7. Single Byte Rea d - The Mast er is reading one address from the MMA745 5L

Figure 8. Multiple Bytes Read - The Master is reading multiple sequen tial registers from the MMA7455L

Figure 9. Single Byte Write - The Master (MCU) is writing to a single register of the MMA7455L

MULTIPLE BYTES WRITE

The MMA7455L automatically increments the received register address commands after a write command is received. Therefore,

after following the steps of a single byte write, multiple bytes of data can be written to sequential registers after each MMA7455L

acknowledgment (ACK) is received. See Figure 10.

Figure 10. Multiple Byte Writes - The Master (MCU) is writing to multiple sequential registers of the MMA7455L

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18 Freescale Semiconductor

MMA7455L

SPI Slave Interface

The MMA7455L also uses serial peripheral interface communication as a digital communication. The SPI communication is pri-

marily used for synchronous serial communication between a master device and one or more slave devices. See Figure 16 for

an example of how to configure one master with one MMA745xL device. The MMA7455L is always operated as a slave device.

Typically, th e master device would be a microcontroll er which would drive the clock (SPC) and chip select (CS) signals.

The SPI interface consists of two control lines and two data lines: CS, SPC, SDI, and SDO. The CS, also known as Chip Select,

is the slave device enable which is controlled by the SPI master . CS is driven low at the start of a transmission. CS is then driven

high at the end of a transmission. SPC is the Serial Port Clock which is also controlled by the SPI master. SDI and SDO are the

Serial Port Data Input and the Serial Port Data Output. The SDI and SDO data lines are driven at the falling edge of the SPC and

should be captured at the rising edge of the SPC.

Read and write register commands are completed in 16 clock pulses or in multiples of 8, in the case of a multiple byte read/write.

SPI Read Operation

A SPI read transfer consists of a 1-bit Read/Write signal, a 6-bit address, and 1-bit don’t care bit. (1-bit R/W=0 + 6-bits address

+ 1-bit don’t care). The data to read is sent by the SPI interface during the next transfer. See Figure 11 and Figure 12 for the

timing diagram for an 8-bit read in 4 wire and 3 wire modes, respec tively.

SPI Write Operation

In order to write to one of the 8-bit registers, an 8-bit write command must be sent to the MMA7455L. The write command consists

of an MSB (0=read, 1=write) to indicate writing to the MMA7455L register, followed by a 6-bit address and 1 don’t care bit.

The command should then be followed th e 8-bit data transfe r. See Figure 13 for the timing diagram for an 8-bit data write.

Figure 11. SPI Timing Diagram for 8-Bit Register Read (4 Wire Mode)

Figure 12. SPI Timing Diagram for 8-Bit Register Read (3 Wire Mode)

Figure 13. SPI Timing Diagram for 8-Bit Register Write (3 Wire Mode)

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BASIC CONNECTIONS

Pin Descriptions

Figure 14. Pinout Description

Table 8. Pin Descriptions

Recommended PCB Layout for Interfacing Accelerometer to Microcontroller

Figure 15. I2C Connection to MCU

8913

10 11

165432

AVDD

GND

DVDD_IO

SCL/SPCCS

INT1/DRDY

INT2

N/C

SDO

SDA/SDI/SDO

N/C

IADDR0 N/C

GND

Top View 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 I2C Address Bit 0 Input

5 GND Ground Input

6 AVDD Analog Power Input

7CS

SPI Enable (0), I2C Enable (1) Input

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 No internal connection. Leave

unconnected or connect to Ground. Input

12 SDO SPI Serial Data Output Output

13 SDA/SDI/SDO I2C Serial Data (SDA), SPI Serial

Data Input (SDI), 3-wire interface

Serial Data Output (SDO)

Open

Drain/

Input/

Output

14 SCL/SPC I2C Serial Clock (SCL), SPI Serial

Clock (SPC)

Input

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Figure 16. SPI Connection to MCU

NOTES:

1. Us e a 0 . 1 μF and a 10 μF capacitor on AVDD to and DVDD to decouple the power source.

2. Physical coupling distance of the accelerometer to the microcontroller shoul d be minimal.

3. PCB layout of power and ground should not couple power supply noise.

4. Accelerometer and microcontroller should not be a high current path.

5. Any external power supply switching frequency should be selected such that they do not interfere with the internal

accelerometer sampling frequency (sampling frequency). This will prevent aliasing errors.

6. Physical distance of the two GND pins (Pin 2 and Pin 5) tied together should be at the shortest distance.

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Freescale Semiconductor 21

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Signed byte data (2’s complement): 0g = 10’h000

Reading low byte XOUTL latches high byte XOUTH to allow 10-bit reads.

XOUTH should be read directly following XOUTL read.

Table 9. User Register Summary

Address Name Definition Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

$00 XOUTL 10 bits output value X LSB XOUT[7] XOUT[6] XOUT[5] XOUT[4] XOUT[3] XOUT[2] XOUT[1] XOUT[0]

$01 XOUTH 10 bits output value X MSB -- -- -- -- -- -- XOUT[9] XOUT[8]

$02 YOUTL 10 bits output value Y LSB YOUT[7] YOUT[6] YOUT[5] YOUT[4] YOUT[3] YOUT[2] YOUT[1] YOUT[0]

$03 YOUTH 10 bits output value Y MSB -- -- -- -- -- -- YOUT[9] YOUT[8]

$04 ZOUTL 10 bits output value Z LSB ZOUT[7] ZOUT[6] ZOUT[5] ZOUT[4] ZOUT[3] ZOUT[2] ZOUT[1] ZOUT[0]

$05 ZOUTH 10 bits output value Z MSB -- -- -- -- -- -- ZOUT[9] ZOUT[8]

$06 XOUT8 8 bits output value X XOUT[7] XOUT[6] XOUT[5] XOUT[4] XOUT[3] XOUT[2] XOUT[1] XOUT[0]

$07 YOUT8 8 bits output value Y YOUT[7] YOUT[6] YOUT[5] YOUT[4] YOUT[3] YOUT[2] YOUT[1] YOUT[0]

$08 ZOUT8 8 bits output value Z ZOUT[7] ZOUT[6] ZOUT[5] ZOUT[4] ZOUT[3] ZOUT[2] ZOUT[1] ZOUT[0]

$09 STATUS Status registers -- -- -- -- -- PERR DOVR DRDY

$0A DETSRC Detection source regist ers LDX LDY LDZ PDX PDY PDZ INT2 INT1

$0B TOUT “Temperature output value” (Optional) TMP[7] TMP[6] TMP[5] TMP[4] TMP[3] TMP[2] TMP[1] TMP[0]

$0C (Reserved) -- -- -- -- -- -- -- --

$0D I2CAD I2C device address I2CDIS DAD[6] DAD[5] DAD[4] DAD[3] DAD[2] DAD[1] DAD[0]

$0E USRINF User information (Optional) UI[7] UI[6] UI[5] UI[4] UI[3] UI[2] UI[1] UI[0]

$0F WHOAMI “Who am I” value (Optional) ID[7] ID[6] ID[5] ID[4] ID[3] ID[2] ID[1] ID[0]

$10 XOFFL Offset drift X value (LSB) XOFF[7] XOFF[6] XOFF[5] XOFF[4] XOFF[3] XOFF[2] XOFF[1] XOFF[0]

$11 XOFFH Offset drift X value (MSB) -- -- -- -- -- XOFF[10] XOFF[9] XOFF[8]

$12 YOFFL Offset drift Y value (LSB) YOFF[7] YOFF[6] YOFF[5] YOFF[4] YOFF[3] YOFF[2] YOFF[1] YOFF[0]

$13 YOFFH Offset drift Y value (MSB) -- -- -- -- -- YOFF[10] YOFF[9] YOFF[8]

$14 ZOFFL Offset drift Z value (L S B) ZOFF[7] ZOFF[6] ZOFF[5] ZOFF[4] ZOFF[3] ZOFF[2] ZOFF[1] ZOFF[0]

$15 ZOFFH Offset drift Z value (MSB) -- -- -- -- -- ZOFF[10] ZOFF[9] ZOFF[8]

$16 MCTL Mode control -- DRPD SPI3W STON GLVL[1] GLVL[0] MOD[1] MOD[0]

$17 INTRST Interrupt latch reset -- -- -- -- -- -- CLRINT2 CLRINT1

$18 CTL1 Control 1 DFBW THOPT ZDA YDA XDA INTRG[1] INTRG[0] INTPIN

$19 CTL2 Control 2 -- -- -- -- -- DRVO PDPL LDPL

$1A LDTH Level detection threshold limit value LDTH[7] LDTH[6] LDTH[5] LDTH[4] LDTH[3] LDTH[2] LDTH[1] LDTH[0]

$1B PDTH Pulse detection threshold limit value PDTH[7] PDTH[6] PDTH[5] PDTH[4] PDTH[3] PDTH[2] PDTH[1] PDTH[0]

$1C PW Pulse duration value PD[7] PD[6] PD[5] PD[4] PD[3] PD[2] PD[1] PD[0]

$1D LT Latency time value LT[7] LT[6] LT[5] LT[4] LT[3] LT[2] LT[1] LT[0]

$1E TW Time window for 2nd pulse value TW[7] TW[6] TW[5] TW[4] TW[3] TW[2] TW[1] TW[0]

$1F (Reserved) -- -- -- -- -- -- -- --

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

D7 D6 D5 D4 D3 D2 D1 D0 Bit

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

00000000Default

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Signed byte data (2’s complement): 0g = 10’h000

Reading low byte XOUTL latches high byte XOUTH to allow 10-bit reads.

XOUTH should be read directly following XOUTL read.

Signed byte data (2’s complement): 0g = 10’h000

Reading low byte YOUTL latches hi gh byte YOUTH to allow coherent 10-bit reads.

YOUTH should be read directly following YOUTL.

Signed byte data (2’s complement): 0g = 10’h000

Reading low byte ZOUTL latches high byte ZOUTH to allow coherent 10-bit reads.

ZOUTH should be read directly following ZOUTL.

Signed byte data (2’s complement): 0g = 10’h000

Reading low byte ZOUTL latches high byte ZOUTH to allow coherent 10-bit reads.

ZOUTH should be read directly following ZOUTL.

Signed byte data (2’s complement): 0g = 8’h00

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

D7 D6 D5 D4 D3 D2 D1 D0 Bit

-- -- -- -- -- -- XOUT [9] XOUT[8] Function

00000000Default

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

D7 D6 D5 D4 D3 D2 D1 D0 Bit

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

00000000Default

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

D7 D6 D5 D4 D3 D2 D1 D0 Bit

-- -- -- -- -- -- YOUT [9] YOUT[8] Function

0 0 0 0 0 0 0 0 Default

$04: 10bits Output Value Z LSB (Read only)

D7 D6 D5 D4 D3 D2 D1 D0 Bit

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

00000000Default

$05: 10bits Output Value Z MSB (Read only)

D7 D6 D5 D4 D3 D2 D1 D0 Bit

-- -- -- -- -- -- ZOUT [9] ZOUT[8] Function

00000000Default

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

D7 D6 D5 D4 D3 D2 D1 D0 Bit

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

00000000Default

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

D7 D6 D5 D4 D3 D2 D1 D0 Bit

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

00000000Default

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Signed byte data (2’s complement): 0g = 8’h00

DRDY

1: Data is ready

0: Data is not ready

DOVR

1: Data is over written

0: Data is not over written

PERR

1: Parity error is detected in trim data. Then, self-test is dis-

abled

0: Parity error is not detected in trim data

LDX

1: Level detection detected on X-a xis

0: Level detection not detected on X-axis

LDY

1: Level detection detected on Y-axis

0: Level detection not detected on Y-axis

LDZ

1: Level detection detected on Z-axis

0: Level detection not detected on Z-axis

PDX *Note

1: Pulse is detected on X-axis at single pulse detection

0: Pulse is not detected on X-axis at single pulse detection

PDY *Note

1: Pulse is detected on Y-axis at single pulse detection

0: Pulse is not detected on Y- axis at single pulse detection

PDZ *Note

1: Pulse is detected on Z-axis at single pulse detection

0: Pulse is not detected on Z-axis at single pulse detection

Note: This bit value is not valid at double pulse detection

INT1

1: Interrupt assigned by INTRG[1:0] bits in Control 1

0: Interrupt assigned by INTRG[1:0] bits in Control 1

INT2

1: Interrupt assigned by INTRG[1:0] bits in Control 1

0: Interrupt assigned by INTRG[1:0] bits in Control 1

*Note: Must define DRDY to be an output to either INT1 or

not. This is done through bit DRPD located in Register $16.

I2CDIS

0: I2C and SPI are available.

1: I2C is disabled.

DVAD[6:0]: I2C device address

UI2[7:0]: User information

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

D7 D6 D5 D4 D3 D2 D1 D0 Bit

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

00000000Default

$09: Status Register (Read on ly)

D7 D6 D5 D4 D3 D2 D1 D0 Bit

-- -- -- -- -- PERR DOVR DRDY Function

0 0 0 0 0 0 0 0 Default

$0A: Detection Source Register (Read on ly)

D7 D6 D5 D4 D3 D2 D1 D0 Bit

LDX LDY LDZ PDX PDY PDZ INT2 INT1 Function

00000000Default

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

D7 D6 D5 D4 D3 D2 D1 D0 Bit

I2CDIS DVAD[6] DVAD[5] DVAD[4] DVAD[3] DVAD[2] DVAD[1] DVAD[0] Function

00011101Default

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

D7 D6 D5 D4 D3 D2 D1 D0 Bit

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

0/OTP 0/OTP 0/OTP 0/OTP 0/OTP 0/OTP 0/OTP 0/OTP Default

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Signed byte data (2’s complement): User level offset trim value for X-axis

*Bit weight is for 8g 10-bit data output. Typical value for reference only. Variation is specified in “Electrical Characteristics” section.

Signed byte data (2’s complement): User level offset trim value for X-axis

Signed byte data (2’s complement): User level offset trim value for Y-axis

*Bit weight is for 2g 8-bit data output. Typical value for reference only. Variation is specified in “Electrical Characteristics” section.

Signed byte data (2’s complement): User level offset trim value for Y-axis

*Bit weight is for 2g 8-bit data output. Typical value for reference only. Variation is specified in “Electrical Characteristics” section.

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

D7 D6 D5 D4 D3 D2 D1 D0 Bit

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

0/OTP 0/OTP 0/OTP 0/OTP 0/OTP 0/OTP 0/OTP 0/OTP Default

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

The following Offset Drift Registers are used for setting and storing the offset calibrations to eliminate the 0g offset. Please refer

to Freescale application note AN3745 for detailed instructions on the process to set and store the calibration values.

D7 D6 D5 D4 D3 D2 D1 D0 Bit

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

00000000Default

Bit XOFF[7] XOFF[6] XOFF[5] XOFF[4] XOFF[3] XOFF[2] XOFF[1] XOFF[0]

Weight* 64 LSB 32 LSB 16 LSB 8 LSB 4 LSB 2 LSB 1 LSB 0.5 LSB

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

D7 D6 D5 D4 D3 D2 D1 D0 Bit

-- -- -- -- -- XOFF [10] XOFF [9] XOFF [8] Function

00000000Default

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

D7 D6 D5 D4 D3 D2 D1 D0 Bit

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

00000000Default

Bit YOFF[7] YOFF[6] YOFF[5] YOFF[4] YOFF[3] YOFF[2] YOFF[1] YOFF[0]

Weight* 64 LSB 32 LSB 16 LSB 8 LSB 4 LSB 2 LSB 1 LSB 0.5 LSB

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

D7 D6 D5 D4 D3 D2 D1 D0 Bit

-- -- -- -- -- YOFF [10] YOFF [9] YOFF [8] Function

00000000Default

Bit YOFF[10] YOFF[9] YOFF[8]

Weight* Polarity 256 LSB 128 LSB

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Signed byte data (2’s complement): User level offset trim value for Z-axis

*Bit weight is for 2g 8-bit data output. Typical value for reference only. Variation is specified in “Electrical Characteristics” section.

Signed byte data (2’s complement): User level offset trim value for Z-axis

*Bit weight is for 2g 8-bit data output. Typical value for reference only. Variation is specified in “Electrical Characteristics” section.

GLVL [1:0]

00: 8g is selected for measurement range.

10: 4g is selected for measurement range.

01: 2g is selected for measurement range.

STON

0: Self-test is not enabled

1: Self-test is enabled

MODE [1:0]

00: Standby Mode

01: Measurement Mode

10: Level Dete cti o n Mo de

11: Pulse Detection Mode

SPI3W

0: SPI is 4 wire mode

1: SPI is 3 wire mode

DRPD

0: Data ready status is output to INT1/DRDY PIN

1: Data ready status is not output to INT1/DRDY PIN

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

D7 D6 D5 D4 D3 D2 D1 D0 Bit

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

00000000Default

Bit ZOFF[7] ZOFF[6] ZOFF[5] ZOFF[4] ZOFF[3] ZOFF[2] ZOFF[1] ZOFF[0]

Weight* 64 LSB 32 LSB 16 LSB 8 LSB 4 LSB 2 LSB 1 LSB 0.5 LSB

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

D7 D6 D5 D4 D3 D2 D1 D0 Bit

-- -- -- -- -- ZOFF[10] ZOFF[9] ZOFF[8] Function

00000000Default

Bit ZOFF[10] ZOFF[9] ZOFF[8]

Weight* Polarity 256 LSB 128 LSB

$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

00000000Default

Table 10. 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

Table 11. Configuring the Mode us in g Reg ist er $16 with MODE[1:0] bits

MODE [1:0] Function

00 Standby Mode

01 Measurement Mode

10 Level Detection Mode

11 Pulse Detection Mode

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CLR_INT1

1: Clear “INT1” and LDX/LDY/LDZ or PDX/PDY/PDZ bits in Detection Source Register ($0A) depending on

Control1($18) INTREG[1:0] setting.

0: Do not clear “INT1” LDX/LDY/LDZ or PDX/PDY/PDZ bits in Detection Source Register ($0A)

CLR_INT2

1: Clear “INT2” and LDX/LDY/LDZ or PDX/PDY/PDZ bits in Detection Source Register ($0A) depending on

Control1($18) INTREG[1:0] setting.

0: Do not clear “INT2” and LDX/LDY/LDZ or PDX/PDY/PDZ bits in Detection Source Register ($0A).

00: INT1 Register is detecting Level while INT2 is detecting Pulse.

01: INT1 Register is detecting Pulse while INT2 is detecting Level.

10: INT1 Register is detecting a Single Pulse and INT2 is detecting Single Pulse (if 2nd T ime Window = 0) or if there is a latency

time window and second time window > 0 then INT2 will detect the doubl e pulse only.

INTPIN: INT1 pin is routed to INT1 bit in Detection Source Register ($0A) and INT2 pin is routed to INT2 bit in Detection Source

INTPIN: INT2 pin is routed to INT1 bit in Detection Source Register ($0A) and INT1 pin is routed to INT2 bit in Detection Source

XDA

1: X-axis is disabled for detection.

0: X-axis is enabled for detection.

YDA

1: Y-axis is disabled for detection.

0: Y-axis is enabled for detection.

ZDA

1: Z-axis is disabled for detection.

0: Z-axis is enabled for detection.

THOPT (This bit is valid for level detecti on only , no t valid

for pulse detection)

0: Threshold value is absolute only

1: Integer value is available.

DFBW

0: Digital filter band width is 62.5 Hz

1: Digital filter band width is 125 Hz

LDPL

0: Level detection polarity is positive and detecting condition

is OR 3 axes.

1: Level detection polarity is negative detecting condition is

AND 3 axes.

PDPL

0: Pulse detection polarity is positive and detecting condition

is OR 3 axes.

1: Pulse detection polarity is negative and detecting condition

is AND 3 axes.

DRVO

0: Standard drive strength on SDA/SDO pin

1: Stro ng drive strength on SDA/SDO pin

$17: Interrupt Latch Reset (Read/Write)

D7 D6 D5 D4 D3 D2 D1 D0 Bit

-- -- -- -- -- -- CLR_INT2 CLR_INT1 Function

00000000Default

$18 Control 1 (Read/Write)

D7 D6 D5 D4 D3 D2 D1 D0 Bit

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

00000000Default

Table 12. Configuring the Interrupt setti ngs using Register $18 with INTREG[1:0] bits

INTREG[1:0] “INT1” Register Bit “INT2” Register Bit

00 Level detection Pulse Detection

01 Pulse Detection Level Detection

10 Single Pulse detection Single or Double Pulse Detection

$19: Control 2 (Read/Write)

D7 D6 D5 D4 D3 D2 D1 D0 Bit

DRVO PDPL LDPL Function

00000000Default

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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.

PDTH[6:0]: Pulse detection th reshold value (unsigned 7 bits).

XPDTH: This bit should be “0”.

Min: PD[7:0] = 4’h 0 1 = 0. 5 ms

Max: PD[7:0] = 4’hFF = 127 ms

1 LSB = 0.5 ms

Min: LT[7:0] = 8’h01 = 1 ms

Max: LT[7:0] = 8’hFF = 255 ms

1 LSB = 1 ms

Min: TW[7:0] = 8’ h01 = 1 ms (Single pulse detection)

Max: TW[7:0] = 8’hFF = 255 ms

1 LSB = 1 ms

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

D7 D6 D5 D4 D3 D2 D1 D0 Bit

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

00000000Default

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

D7 D6 D5 D4 D3 D2 D1 D0 Bit

XPDTH PDTH[6] PDTH[5] PDTH[4] PDTH[3] PDTH[2] PDTH[1] PDTH[0] Function

00000000Default

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

D7 D6 D5 D4 D3 D2 D1 D0 Bit

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

00000000Default

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

D7 D6 D5 D4 D3 D2 D1 D0 Bit

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

00000000Default

$1E: Time Window for 2n d Pulse Value (Read/Write )

D7 D6 D5 D4 D3 D2 D1 D0 Bit

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

00000000Default

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SENSING DIRECTION AND OUTPUT RESPONSE

The following figure shows sensing direction and the output response for 2g mode.

Figure 17. Sensing Direc tio n and Output Respon se at 2g Mode

Table 1 3. Acceleration vs. Output (8-bit data)

FS Mode Acceleration Output

2g Mode -2g $80

-1g $C1

0g $00

+1g $3F

+2g $7F

4g Mode -4g $80

-1g $E1

0g $00

+1g $1F

+4g $7F

8g Mode -8g $80

-1g $F1

0g $00

+1g $0F

+8g $7F

Side View

XOUT @0g=$00

YOUT @ +1g = $3F

ZOUT @0g=$00

XOUT @ +1g = $3F

YOUT @0g=$00

ZOUT @0g=$00

XOUT @ -1g = $C1

YOUT @0g=$00

ZOUT @ 0g = $00

165432

1312111098

147

XOUT @0g=$00

YOUT @ -1g = $C1

ZOUT @0g=$00

Direction of Earth's gravity field.*

Top View

XOUT @0g=$00

YOUT @0g=$00

ZOUT @ -1g = $C1

XOUT @0g=$00

YOUT @0g=$00

ZOUT @ +1g = $3F

165432

1312111098

147

165432

13 12 11 10 9 8

14 7

165432

1312111098

147

Top

Bottom

* When positioned as shown, the Earth’s gravity will result in a positive 1g output.

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Freescale Semiconductor 29

MMA7455L

MINIMUM RECOMMENDED FOOTPRINT FOR SURFACE MOUNTED APPLICATIONS

Surface mount board layout is a critical portion of the to tal design. The footprint for the surface mount packages must be the

correct size to ensure proper solder connection interface between the board and the package.

With the correct footprint, the packages will self-align when subjected to a solder reflow process. It is always recommended to

design boards with a solder mask layer to avoid bridging and shorting between solder pads.

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

These guideline are for soldering and mounting the LGA package inertial sensors to printed circuit boards (PCBs). The purpose

is to minimize the stress on the package after board mounting. The MMA7455L digital output accelerometer uses the Land Grid

Array (LGA) package platform. This section describes suggested methods of soldering these devices to the PC board for con-

sumer applications. Figure 18 shows the recommended PCB land pattern for the package.

Figure 18. Recommended PCB Land Pattern for the 5 x 3 mm LGA Package

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OVERVIEW OF SOLDERING CONSIDERATIONS

Information provided here is based on experiments executed on LGA devices. They do not represe nt exact conditions present

at a customer site. Hence, information herein should be used as a guidance only and process and design optimizations are

recommended to develop an application specific solution. It should be noted that with the proper PCB footprint and solder stencil

designs the package will self-align during the solder reflow process.

The following are the recommended guidelines to follow for mounting LGA sensors for consumer applications.

PCB MOUNTING RECOMMENDATIONS

1. The PCB land should be designed with Non Solder Mask Defined (NSMD) as shown in Figure 21.

2. No additional metal pattern underneath package as shown in Figure 20.

3. PCB land pad is 0.9 mm x 0.6 mm which is the size of the package pad plus 0.1 mm as shown in Figure 21.

4. The solder mask opening is equal to the size of the PCB land pad plus an extra 0.1 mm as shown in Figure 21.

5. The stencil aperture size is equal to the PCB land pad – 0.025mm.

Figure 19. Incorrect PCB Top Metal Pattern Under

Package Figure 20. Correct PCB Top Metal Pattern Under Package

Figure 21. Recommended PCB Land Pad, Solder Mask, and Signal Trace Near Package Design

Exam

le of 2 la

er PCB

Top metal pattern

under package area

Via structure under

LGA

acka

e w/ solder

PCB top metal layer

Top metal pattern

under package area Via structure under

package area

0.8 mm

0.5 mm

PCB land pattern - NSMD

SM opening = P CB land pad + 0.1mm

= 1.0 x 0.7mm sq.

Cu: 0.9 x 0. 6 mm sq.

Signal trace near

package: 0.1mm width

and min. 0.5m m length

are recommended.

Wider trace can be

continued after these.

Wider trace

Pad Dimension by Package

Sensors

Freescale Semiconductor 31

MMA7455L

Figure 22. Stencil Design Guidelines

6. Do not place any components or vias at a distance less than 2 mm from the package land area. This may cause additional

package stress if it is too close to the package land area.

7. Signal traces connected to pads should be as symmetric as possible. Put dummy traces on NC pads in order to have same

length of exposed trace for all pads. Signal traces with 0.1 mm width and min. 0.5 mm length for all PCB land pads near the

package are recommended as shown in Figure 21 and Figure 22. Wider trace can be continued after the 0.5 mm zone.

8. Use a standard pick and place process and equipment. Do not us a hand so ldering process.

9. It is recommended to use a cleanable solder paste with an additional cleaning step after SMT mount.

10. Do not use a screw down or stacking to fix the PCB into an enclosure because this could bend the PCB putting stress on

the pack ag e.

11. The PCB should be rated for the multiple lead-free reflow condition with max 260°C temperature.

Please cross reference with the device data sheet for mounting guidelines specific to the exact device used.

Freescale LGA sensors are compliant with Restrictions on Hazardous Substances (RoHS), having halide free molding compound

(green) and lead-free terminations. These terminations are compatible with tin-lead (Sn-Pb) as well as tin-silver-copper

(Sn-Ag-Cu) solder paste soldering processes. Reflow profiles applicable to those processes can be used successfully for solder-

ing the devices.

14x0.575mm

Stencil opening = PCB landing

pad -0.025mm

= 0.575mmx0 ,8 75m m

Package

footprint

Signal trace near

package

10x0.8mm

14x0.875mm

Sensors

32 Freescale Semiconductor

MMA7455L

Figure 23. MMA7455L Temperature Coefficient of Offset (TCO) and

Temperature Coefficient of Sensitivity (TCS) Distributio n Ch arts

Figure 24. MMA7455L Current Distribution Charts

LSL USLTarget

-0.02 -0.01 00.01 0.02

Ysens_%/DegreeC_-40to85

LSL USLTarget

-0.03 -0.02 -0.01 00.01 0.02 0.03

Zsens_%/DegreeC_-40to85

LSL USLTarget

-3 -2 -1 0 1 2 3

Zoff_mg/degreeC_-40to85

LSL USLTarget

-3 -2 -1 0 1 2 3

Yoff_mg/degreeC_-40to85

LSL USLTarget

-0.02 -0.01 00.01 0.02

Xsens_%/DegreeC_-40to85

LSL USLTarget

-3 -2 -1 0 1 2 3

Xoff_mg/degreeC_-40to85

Sensors

Freescale Semiconductor 33

MMA7455L

PACKAGE DIMENSIONS

CASE 1977-01

ISSUE A

14-LEAD LGA

Sensors

34 Freescale Semiconductor

MMA7455L

PACKAGE DIMENSIONS

CASE 1977-01

ISSUE A

14-LEAD LGA

MMA7455L

Rev. 10

12/2009

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