Freescale Semiconductor Energy Efficient Solutions Xtrinsic MMA8452Q Data Sheet: Technical Data
MMA8452Q
16 PIN QFN
3 mm x 3 mm x 1 mm
CASE 2077-02
Top and Bottom View
Top View
Pin Connections
1
2
3
4
59
10
11
12
13
141516
876
NC
VDD
NC
VDDIO
BYP
DNC
SCL
GND
NC
GND
INT1
GND
INT2
SA0
NC
SDA
Freescale Semiconductor Document Number: MMA8452Q
Data Sheet: Technical Data Rev. 9, 07/2014
An Energy Efficient Solution by Freescale
Xtrinsic MMA8452Q 3-Axis,
12-bit/8-bit Digital Accelerometer
The MMA8452Q is a smart, low-power, three-axis, capacitive, micromachined
accelerometer with 12 bits of resolution. This accelerometer is packed with
embedded functions with flexible user programmable options, configurable to two
interrupt pins. Embedded interrupt functions allow for overall power savings
relieving the host processor from continuously polling data.
The MMA8452Q has user selectable full scales of ±2g/±4g/±8g with high-pass
filter filtered data as well as non-filtered data available real-time. The device can
be configured to generate inertial wakeup interrupt signals from any combination
of the configurable embedded functions allowing the MMA8452Q to monitor
events and remain in a low power mode during periods of inactivity. The
MMA8452Q is available in a 3 mm x 3 mm x 1 mm QFN package.
Features
• 1.95V to 3.6V supply voltage
• 1.6V to 3.6V interface voltage
• ±2g/±4g/±8g dynamically selectable full-scale
• Output Data Rates (ODR) from 1.56 Hz to 800 Hz
• 99 μg/√Hz noise
• 12-bit and 8-bit digital output
2
C
•I
• Two progr ammable interrupt pins for six interrupt sources
• Three embedded channels of motion detection
Typical Applications
• E-Compass applications
• Static orientation detection (Portrait/Landscape, Up/Down, Left/Right, Back/
• Notebook, e-reader, and Laptop Tumble and Freefall Detection
• Real-time orientation detection (virtual reality and gaming 3D user position feedback)
• Real-time activity analysis (pedometer step counting, freefall drop detection for HDD, dead-reckoning GPS backup)
• Motion detection for portable product power saving (Auto-SLEEP and Auto-WAKE for cell phone, PDA, GPS, gaming)
• Shock and vibration monitoring (mechatronic compensation, shipping and warranty usage logging)
•
digital output interface
— Freefall or Motion Detection: 1 channel
— Pulse Detection: 1 channel
— Transient Detection: 1 channel
– Orientation (Portrait/Landscape) detection with set hysteresis
– Automatic ODR change for Auto-WAKE and return to SLEEP
– High-Pass Filter Data available real-time
–Self-Test
– RoHS compliant
– Current Consumption: 6 μA to 165 μA
Front position identification)
User interface (menu scrolling by orientation change, pulse detection for button replacement
Part Number Temperature Range Package Description Shipping
MMA8452QT -40°C to +85°C QFN-16 Tray
MMA8452QR1 -40°C to +85°C QFN-16 Tape and Reel
ORDERING INFORMATION
)
© 2010-2014 Freescale Semiconductor, Inc. All rights reserved.
Contents
1 Block Diagram and Pin Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Soldering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 Mechanical and Electrical Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1 Mechanical Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.2 Electrical Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.3 I2C interface characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.4 Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1 Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2 Zero-g Offset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.3 Self-Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4 System Modes (SYSMOD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5 Functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.1 Device Calibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.2 8-bit or 12-bit Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.3 Low-Power Modes vs. High-Resolution Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.4 Auto-WAKE/SLEEP Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.5 Freefall and Motion Detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.6 Transient Detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.7 Pulse Detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.8 Orientation Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.9 Interrupt Register Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.10 Serial I
6 Register Descriptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6.1 Data Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
6.2 Portrait/ Landscape Embedded Function Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
6.3 Motion and Freefall Embedded Function Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
6.4 Transient (HPF) Acceleration Detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
6.5 Single, Double and Directional Pulse-Detection Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
6.6 Auto-WAKE/SLEEP Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
6.7 Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
6.8 User Offset Correction Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
7 Printed Circuit Board Layout and Device Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
7.1 Printed Circuit Board Layout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
7.2 Overview of Soldering Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
7.3 Halogen Content. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
8 Package Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
8.1 Product identification markings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
8.2 Tape and reel information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
8.3 Package Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
9 Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
2
C Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Related Documentation
The MMA8452Q device features and operations are described in a variety of reference manuals, user guides, and application
notes. To find the most-current versions of these documents:
1. Go to the Freescale homepage at:
http://www.freescale.com/
2. In the Keyword search box at the top of the page, enter the device number MMA8452Q.
3. In the Refine Your Result pane on the left, click on the Documentation link.
MMA8452Q
Sensors
2 Freescale Semiconductor, Inc.
1 Block Diagram and Pin Description
12-bit
SDA
SCL
I2C
Embedded
DSP
Functions
C to V
Internal
OSC
Clock
GEN
ADC
Converter
VDDIO
VSS
X-axis
Transducer
Y-axis
Transducer
Z-axis
Transducer
Freefall
and Motion
Detection
Transient
Detection
(i.e., fast motion,
transient)
Orientation with
Set Hysteresis
and Z-lockout
Shake Detection
through
Motion
Threshold
Auto-WAKE/Auto-SLEEP Configurable with debounce counter and multiple motion interrupts for control
Auto-WAKE/SLEEP
ACTIVE Mode
SLEEP
VDD
INT1
INT2
ACTIVE Mode
WAKE
Single, Double
and Directional
Tap Detection
MODE Options
Low Power
Low Noise + Low Power
High Resolution
Normal
MODE Options
Low Power
Low Noise + Low Power
High Resolution
Normal
1
DIRECTION OF THE
DETECTABLE ACCELERATIONS
(BOTTOM VIEW)
5
9
13
X
Y
Z
1
(TOP VIEW)
Earth Gravity
Figure 1. Block Diagram
Figure 2. Direction of the Detectable Accelerations
Sensors
Freescale Semiconductor, Inc. 3
MMA8452Q
Figure 3 shows the device configuration in the six different orientation modes. These orientations are defined as the following:
Top View
PU
Earth Gravity
Pin 1
Xout @ 0g
Yout @ -1g
Zout @ 0g
Xout @ 1g
Yout @ 0g
Zout @ 0g
Xout @ 0g
Yout @ 1g
Zout @ 0g
Xout @ -1g
Yout @ 0g
Zout @ 0g
LL
PD
LR
Side View
FRONT
Xout @ 0g
Yout @ 0g
Zout @ 1g
BACK
Xout @ 0g
Yout @ 0g
Zout @ -1g
0.1μF
1.6V-3.6V
VDDIO
VDDIO
VDDIO
4.7kΩ 4.7kΩ
1
GND
VDDIO
SCL
NC
INT2
INT1
GND
GND
SDA
SA0
VDD
NC
NC
NC
BYP
NC
MMA8452Q
2
16
12
13
1415
11
10
3
4
5
6
7
8
9
4.7μF
INT1
INT2
SA0
0.1μF
1.95V - 3.6V
VDD
SCL
SDA
DNC
PU = Portrait Up, LR = Landscape Right, PD = Portrait Down, LL = Landscape Left, BACK and FRONT side views. There are
several registers to configure the orientation detection and are described in detail in the register setting section.
Figure 3. Landscape/Portrait Orientation
Figure 4. Application Diagram
MMA8452Q
4 Freescale Semiconductor, Inc.
Sensors
Table 1. Pin Descriptions
Pin # Pin Name Description
1 VDDIO Internal Power Supply (1.62V - 3.6V)
2 BYP Bypass capacitor (0.1 μF)
3 DNC Do not connect to anything, leave pin isolated and floating.
4SCL
5 GND Connect to Ground
6SDA
7SA0
8 NC Internally not connected
9 INT2 Inertial Interrupt 2, output pin
10 GND Connect to Ground
11 INT1 Inertial Interrupt 1, output pin
12 GND Connect to Ground
13 NC Internally not connected
14 VDD Power Supply (1.95 V to 3.6 V)
15 NC Internally not connected
16 NC Internally not connected (can be GND or VDD)
2
C Serial Clock, open drain
I
2
C Serial Data
I
2
I
C Least Significant Bit of the Device I2C Address, I2C 7-bit address = 0x1C (SA0=0), 0x1D (SA0=1).
The device power is supplied through VDD line. Power supply decoupling capacitors (100 nF ceramic plus 4.7 µF bulk, or a
single 4.7 µF ceramic) should be placed as near as possible to the pins 1 and 14 of the device.
The control signals SCL, SDA, and SA0 are not tolerant of voltages more than VDDIO + 0.3V . If VDDIO is removed, the control
signals SCL, SDA, and SA0 will clamp any logic signals with their internal ESD protection diodes.
The functions, the threshold and the timing of the two interrupt pins (INT1 and INT2) are user programmable through the I
2
interface. The SDA and SCL I2C connections are open drain and therefore require a pullup resistor as shown in the application
diagram in Figure 4.
C
1.1 Soldering Information
The QFN package is compliant with the RoHS standard. Please refer to AN4077.
MMA8452Q
Sensors
Freescale Semiconductor, Inc. 5
2 Mechanical and Electrical Specifications
2.1 Mechanical Characteristics
Table 2. Mechanical Characteristics @ VDD = 2.5V, VDDIO = 1.8V, T = 25°C unless ot herwise noted.
Parameter Test Conditions Symbol Min Typ Max Unit
FS[1:0] set to 00
2g Mode
Measurement Range
Sensitivity
Sensitivity Accuracy
Sensitivity Change vs. Temperature
Zero-g Level Offset Accuracy
Zero-g Level Offset Accuracy Post Board Mount
Zero-g Level Change vs. Temperature -40°C to 85°C TCOff ±0.15 mg/°C
Self-Test Output Change
X
Y
Z
ODR Accuracy
2 MHz Clock ±2
Output Data Bandwidth BW ODR/3 ODR/2 Hz
Output Noise Normal Mode ODR = 400 Hz Noise 126 µg/√Hz
Output Noise Low-Noise Mode
Operating Temperature Range Top -40 +85 °C
(1)
(2)
(3)
(4)
(5)
(1)
FS[1:0] set to 01
4g Mode
FS[1:0] set to 10
8g Mode
FS[1:0] set to 00
2g Mode
FS[1:0] set to 01
4g Mode
FS[1:0] set to 10
8g Mode
FS[1:0] set to 00
2g Mode
FS[1:0] set to 01
4g Mode
FS[1:0] set to 10
8g Mode
FS[1:0] 2g, 4g, 8g TyOff ±17 mg
FS[1:0] 2g, 4g, 8g TyOffPBM ±20 mg
FS[1:0] set to 0
4g Mode
Normal Mode ODR = 400 Hz Noise 99 µg/√Hz
FS
So
Soa ±2.64 %
TCSo ±0.008 %/°C
Vst
±2
±4
±8
1024
512
256
+44
+61
+392
counts/g
LSB
g
%
1. Dynamic Range is limited to 4g when the Low-Noise bit in Register 0x2A, bit 2 is set.
2. Sensitivity remains in spec as stated, but changing Oversampling mode to Low Power causes 3% sensitivity shift. This behavior is also seen
when changing from 800 Hz to any other data rate in the Normal, Low Noise + Low Power or High Resolution mode.
3. Before board mount.
4. Post Board Mount Offset Specifications are based on an 8 Layer PCB, relative to 25°C.
5. Self-Test is one direction only.
MMA8452Q
Sensors
6 Freescale Semiconductor, Inc.
2.2 Electrical Characteristics
Table 3. Electrical Characteristics @ VDD = 2.5V, VDDIO = 1.8V, T = 25°C unless otherwise noted.
Parameter Test Conditions Symbol Min Typ Max Unit
Supply Voltage VDD
(1)
Interface Supply Voltage VDDIO
ODR = 1.56 Hz
ODR = 6.25 Hz
ODR = 12.5 Hz 6
Low-Power Mode
ODR = 50 Hz 14
ODR = 100 Hz 24
LP
I
dd
ODR = 200 Hz 44
ODR = 400 Hz 85
ODR = 800 Hz 165
ODR = 1.56 Hz
ODR = 6.25 Hz
ODR = 12.5 Hz 24
Normal Mode
ODR = 50 Hz 24
ODR = 100 Hz 44
I
dd
ODR = 200 Hz 85
ODR = 400 Hz 165
ODR = 800 Hz 165
Current during Boot Sequence, 0.5 mSec max
duration using recommended Bypass Cap
VDD = 2.5V Idd Boot
Value of Capacitor on BYP Pin -40°C 85°C Cap
STANDBY Mode Current @ 25°C
VDD = 2.5V, VDDIO = 1.8V
STANDBY Mode
I
Stby 1.8 5 μA
dd
Digital High Level Input Voltage
SCL, SDA, SA0 VIH 0.7*VDDIO
Digital Low-Level Input Voltage
SCL, SDA, SA0 VIL 0.3*VDDIO
High Level Output Voltage
INT1, INT2 I
= 500 μA VOH 0.9*VDDIO
O
Low-Level Output Voltage
INT1, INT2 I
= 500 μA VOL 0.1*VDDIO
O
Low-Level Output Voltage
SDA I
= 500 μA VOLS 0.1*VDDIO
O
Power on Ramp Time 0.001 1000 ms
Time from VDDIO on and
Boot time
VDD > VDD min until I
2
C is ready
Tbt 350 500 µs
for operation, Cbyp = 100 nF
Turn-on time
Turn-on time
(2)
Time to obtain valid data from
STANDBY mode to ACTIVE mode.
Time to obtain valid data from valid
voltage applied.
Ton1
Ton2 2/ODR + 2 ms
Operating Temperature Range Top -40 +85 °C
1.95 2.5 3.6 V
(1)
1.62 1.8 3.6 V
6
6
24
24
75 100 470 nF
2/ODR + 1 ms
1mA
μA
μA
V
V
V
V
V
s
1. There is no requirement for power supply sequencing. The VDDIO input voltage can be higher than the VDD input voltage.
2. Note the first sample is typically not very precise. Depending on ODR/MODS setting, a minimum of three samples is recommended for full
precision.
MMA8452Q
Sensors
Freescale Semiconductor, Inc. 7
2.3 I2C interface characteristics
VIL = 0.3V
DD
VIH = 0.7V
DD
Table 4. I
2
C slave timing values
SCL clock frequency f
Bus-free time between STOP and START condition t
(Repeated) START hold time t
Repeated START setup time t
STOP condition setup time t
SDA data hold time t
SDA setup time t
SCL clock low time t
SCL clock high time t
SDA and SCL rise time t
SDA and SCL fall time t
SDA valid time
(4)
SDA valid acknowledge time
Pulse width of spikes on SDA and SCL that must be suppressed by
internal input filter
(1)
Parameter Symbol
(5)
SCL
BUF
HD;STA
SU;STA
SU;STO
HD;DAT
SU;DAT
LOW
HIGH
r
f
t
VD;DAT
t
VD;ACK
t
SP
2
C Fast Mode
I
Min Max
0 400 kHz
1.3 μs
0.6 μs
0.6 μs
0.6 μs
0.05 0.9
(2)
100 ns
1.3 μs
0.6 μs
20 + 0.1 C
20 + 0.1 C
(3)
b
(3)
b
300 ns
300 ns
(2)
0.9
(2)
0.9
050ns
Capacitive load for each bus line Cb 400 pF
Unit
μs
μs
μs
1.All values referred to V
2.This device does not stretch the LOW period (t
(0.3VDD) and V
IH(min)
3.Cb = total capacitance of one bus line in pF.
4.t
5.t
= time for data signal from SCL LOW to SDA output (HIGH or LOW, depending on which one is worse).
VD;DAT
= time for Acknowledgement signal from SCL LOW to SDA output (HIGH or LOW, depending on which one is worse).
VD;ACK
(0.7VDD) levels.
IL(max)
) of the SCL signal.
LOW
Figure 5. I2C slave timing diagram
MMA8452Q
Sensors
8 Freescale Semiconductor, Inc.
2.4 Absolute Maximum Ratings
This device is sensitive to mechanical shock. Improper handling can cause permanent damage of the part or
cause the part to otherwise fail.
This device is sensitive to ESD, improper handling can cause permanent damage to the part.
Stresses above those listed as “absolute maximum ratings” may cause permanent damage to the device. Exposure to
maximum rating conditions for extended periods may affect device reliability.
Table 5. Maximum Ratings
Rating Symbol Value Unit
Maximum Acceleration (all axes, 100 μs) g
Supply Voltage VDD -0.3 to + 3.6 V
Input voltage on any control pin (SA0, SCL, SDA) Vin -0.3 to VDDIO + 0.3 V
Drop Test D
Operating Temperature Range T
Storage Temperature Range T
max
drop
OP
STG
Table 6. ESD and Latchup Protection Characteristics
Rating Symbol Value Unit
Human Body Model HBM ±2000 V
Machine Model MM ±200 V
Charge Device Model CDM ±500 V
Latchup Current at T = 85°C
— ±100 mA
5,000 g
1.8 m
-40 to +85 °C
-40 to +125 °C
3 Terminology
3.1 Sensitivity
The sensitivity is represented in counts/g. In 2g mode the sensitivity is 1024 counts/g. In 4g mode the sensitivity is
512 counts/g and in 8g mode the sensitivity is 256 counts/g.
3.2 Zero-g Offset
Zero-g Offset (TyOff) describes th e deviation of an actual output signal from the ideal output signal if the sensor is stationary. A
sensor stationary on a horizontal surface will measure 0g in X-axis and 0g in Y-axis whereas the Z-axis will measure 1g. The output
is ideally in the middle of the dynamic range of the sensor (content of OUT Registers 0x00, data expressed as 2's complement
number). A deviation from ideal value in this case is called Zero-g offset. Offset is to some ex tent a result of stress on the MEMS
sensor and therefore the offset can slightly change aft er mo un ting the sensor onto a printed circuit board or exposin g it to
extensive mechanical stress.
3.3 Self-Test
Self-Test checks the transducer functionality without external mechanical stimulus. When Self-Test is activated, an electrostatic
actuation force is applied to the sensor, simulating a small acceleration. In this case, the sensor outputs will exhibit a change in
their DC levels which are related to the selected full scale through the device sensitivity . When Self-Test is activated, the device
output level is given by the algebraic sum of th e signals produced by the acceleration acting on the se nsor and by the electrostatic
test-force.
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Freescale Semiconductor, Inc. 9
MMA8452Q
4 System Modes (SYSMOD)
OFF
WAKESTANDBY
OFF
ACTIVE
SYSMOD = 00
SYSMOD = 10
SYSMOD = 01
Auto SLEEP/WAKE
Condition
VDD > 1.8 V
VDD < 1.8 V
CTRL_REG1
Active bit = 1
CTRL_REG1
Active bit = 0
CTRL_REG1
Active bit = 0
Figure 6. MMA8451Q Mode Transition Diagram
Table 7. Mode of Operation Description
Mode
OFF
STANDBY
ACTIVE
(WAKE/SLEEP)
Powered Down
I2C communication is possible
I2C communication is possible
2
I
C Bus State
VDDIO Can be > VDD
VDD Function Description
<1.8V
>1.8V
>1.8V
• The device is powered off.
• All analog and digital blocks are shutdown.
2
C bus inhibited.
•I
• Only digital blocks are enabled.
Analog subsystem is disabled.
• Internal clocks disabled.
• Registers accessible for Read/Write.
• Device is configured in STANDBY mode.
• All blocks are enabled (digital, analog).
All register contents are preserved when transitioning from ACTIVE to STANDBY mode. Some registers are reset when
transitioning from STANDBY to ACTIVE. These are all noted in the device memory map register table. The SLEEP and WAKE
modes are ACTIVE modes. For more information on how to use the SLEEP and WAKE modes and how to transition between
these modes, please refer to the functionality section of this document.
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10 Freescale Semiconductor, Inc.
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5 Functionality
The MMA8452Q is a low-power , digital output 3-axis linear accelerometer wit h a I2C interface and embedded logic used to
detect events and notify an external microprocessor over interrupt lines. The functionality includes the following:
• 8-bit or 12-bit data which includes High-Pass Filtered data
• 4 different oversampling options for compromising between resolution and current consumption based on application
requirements
• Additional Low-Noise mode that functions independently of the Oversampling modes for higher resolution
• L ow Power and Auto-WAKE/SLEEP modes for conservation of current consumption
• Single-/Double-pulse with directional information 1 channel
• Motion detection with directional information or Freefall 1 channel
• Transient detection based on a high-pass filter and settable threshold for detecting the change in acceleration above a
threshold with directional information 1 channel
• Portrait/Landscape detection with trip points fixed at 30° and 60° for smooth transitions between orientations.
All functionality is available in 2g, 4g or 8g dynamic ra nges. There are many configuration settings for enabling all the different
functions. Separate application notes have been provided to help configure the device for each embedd ed functionality.
Table 8. Features of the MMA845xQ devices
Feature List MMA8451 MMA8452 MMA8453
Digital Resolution (Bits)
Digital Sensitivity (Counts/g)
Data-Ready Interrupt
Single-Pulse Interrupt
Double-Pulse Interrupt
Directional-Pulse Interrupt
Auto-WAKE
Auto-SLEEP
Freefall Interrupt
32 Level FIFO
High-Pass Filter
Low-Pass Filter
Orientation Detection Portrait/Landscape = 30°, Landscape to Portrait = 60°,
and Fixed 45° Threshold
Programmable Orientation Detection
Motion Interrupt with Direction
Transient Detection with High-Pass Filter
Low Power Mode
14 12 10
4096 1024 256
Yes Yes Yes
Yes Yes Yes
Yes Yes Yes
Yes Yes Yes
Yes Yes Yes
Yes Yes Yes
Yes Yes Yes
Yes No No
Yes Yes Yes
Yes Yes Yes
Yes Yes Yes
Yes No No
Yes Yes Yes
Yes Yes Yes
Yes Yes Yes
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5.1 Device Calibration
The device interface is factory calibrated for sensitivity and Zero-g offset for each axi s . The trim values are stored in Non
Volatile Memory (NVM). On power-up, the trim parameters are read from NVM and applied to the circuitry. In normal use, further
calibration in the end application is not necessary. However, the MMA8452Q allows the user to adjust the Zero-g offset for each
axis after power-up, changing the default offs et values. The user offset adjustments are stored in 6 volatile registers. For more
information on device calibration, refer to Freescale application note, AN4069.
5.2 8-bit or 12-bit Data
The measured acceleration data is stored in the OUT_X_MSB, OUT_X_LSB, OUT_Y_MSB, OUT_Y_LSB, OUT_Z_MSB, and
OUT_Z_LSB registers as 2’s complement 12-bit numbers. The most significant 8-bits of each axis are stored in OUT_X (Y,
Z)_MSB, so applications needing only 8-bit results can use these 3 registers and ignore OUT_X,Y, Z_LSB. To do this, the
F_READ bit in CTRL_REG1 must be set. When the F_READ bit is cleared, the fast read mode is disabled.
When the full-scale is set to 2g, the measurement range is -2g to +1.999g, and each count corresponds to 1g/1024
(1 mg) at 12-bits resolution. When the full-scale is set to 8g, the measu rement range is -8g to +7.996g, and each count
corresponds to 1g/256 (3.9 mg) at 12-bits resolu tion. The resolutio n is reduced by a factor of 16 if only the 8-bit result s are used.
For more information on the data manipulation between data formats and modes, refer to Freescale application note, AN4076.
There is a device driver available that can be used with the Sensor Toolbox demo board (LFSTBEB8451, 2, 3Q).
5.3 Low-Power Modes vs. High-Resolution Modes
The MMA8452Q can be optimized for lower power modes or for higher resolution of the output data. High resolution is
achieved by setting the LNOISE bit in Register 0x2A. This improves the resolution but be aware that the dynamic range is limited
to 4g when this bit is set. This will affect all internal functions and reduce noise. Another method for improving the resolution of
the data is by oversampling. One of the oversampling schemes of the data can activated when MODS = 10 in Register 0x2B
which will improve the resolution of the output data only. The highest resolution is achieved at 1.56 Hz.
There is a trade-off between low power and high resolution. Low Power can be achieved when the oversampling rate is
reduced. The lowest power is achieved when MODS = 11 or when the sample rate is set to 1.56 Hz. For more information on
how to configure the MMA8452Q in Low-Power mode or High-Resolution mode and to realize the benefits
application note, AN4075.
, refer to Freescale
5.4 Auto-WAKE/SLEEP Mode
The MMA8452Q can be configured to transition between sample rates (with their respective current consumption) based on
four of the interrupt functions of the device. The advantage of using the Auto-WAKE/SLEEP is that the system can automatically
transition to a higher sample rate (higher current consumption) when needed but spends the majority of the time in the SLEEP
mode (lower current) when the device does not require higher sampling rates. Auto-WAKE refers to the device being triggered by
one of the interrupt functions to transition to a higher sample rate. This may also interrupt the processor to transition from a SLEEP
mode to a higher power mode.
SLEEP mode occurs after the accelerometer has not detected an interrupt for longer than the user definable time-out period.
The device will transition to the specified lower sample rate. It may also alert the processor to go into a lower power mode to save
on current during this period of inactivity.
The Interrupts that can WAKE the device from SLEEP are the following: P ul s e Detection, Orientation Detection, Motion/Freefall,
and Transient Detection. Refer to AN4074, for more detailed information for configuring the Auto-WAKE/SLEEP.
5.5 Freefall and Motion Detection
MMA8452Q has flexible interrupt architecture for detecting either a Freefall or a Motion. Freefall can be enabled where the set
threshold must be less than the configured threshold, or motion can be enabled where the set threshold must be greater than
the threshold. The motion configuration has the option of enabling or disabling a high-pass filter to eliminate tilt data (static offset).
The freefall does not use the high-pass filter. For details on the Freefall and Motion detection with specific application examples
and recommended configuration settings, refer to Freescale application note, AN4070.
5.5.1 Freefall Detection
The detection of “Freefall” involves the monitoring of the X, Y, and Z axes for the condition where the acceleration magnitude
is below a user specified threshold for a user definable amou nt of time. Norma lly, the usable th re sho ld ran ges are be tw een
±100 mg and ±500 mg.
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12 Freescale Semiconductor, Inc.
5.5.2 Motion Detection
Motion is often used to simply alert the main processor that the device is currently in use. When the acceleration exceeds a
set threshold the motion interrupt is asserted. A motion can be a fast moving shake or a slow moving tilt. This will depend on the
threshold and timing values configured for the ev en t. The motion detection function can analyze static acceleration changes or
faster jolts. For example, to detect that an object is spinning, all three axes would be enabled with a threshold detection of > 2g.
This condition would need to occur for a minimum of 100 ms to ensure that the event wasn't just noise. The timing value is set
by a configurable debounce counter. The debounce counter acts like a filter to determine whether the condition exists for
configurable set of time (i.e., 100 ms or longer). There is also directional data available in the source register to detect the
direction of the motion. This is useful for applications such as directional shake or flick, which assists with the algorithm for various
gesture detections.
5.6 Transient Detection
The MMA8452Q has a built-in high-pass filter. Acceleration data goes through the high-pass filter, eliminating the offset (DC)
and low frequencies. The high-pass filter cutoff frequency can be set by the user to four different frequen ci es w hi c h a re
dependent on the Output Dat a Rate (ODR). A higher cutoff frequency ensures the D C dat a or slower moving da ta will be filtered
out, allowing only the higher frequencies to pass. The embedded Transient Detection function uses the high-pass filtered data
allowing the user to set the threshold and debounce counter. The Transient detection feature can be used in the same manner
as the motion detection by bypassing the high-pass filter. There is an option in the configuration register to do this. This adds
more flexibility to cover various customer use cases.
Many applications use the accelerometer’s static acceleration readings (i.e., tilt) which measure the change in acceleration
due to gravity only. These functions benefit from acceleration dat a being filt ered with a low -p ass filter w here high-freque ncy data
is considered noise. However, there are many functions where the accelerometer must analyze dynamic acceleration. Functions
such as tap, flick, shake and step counting are based on the analysis of the change in the acceleration. It is simpler to interpret
these functions dependent on dynamic acceleration data when the static component has been removed. The Transient Detection
function can be routed to either interrupt pin through bit 5 in CTRL_REG5 register (0x2E). Registers 0x1D – 0x20 are the
dedicated Transient Detection configuration registers. The source register contains directional data to determine the direction of
the acceleration, either positive or negative. For details on the benefits of the embedded Transient Detection function along with
specific application examples and recommended configuration settings, please refer to Freescale application note, AN4071.
5.7 Pulse Detection
The MMA8452Q has embedded single/double and directional pulse detection. This function has various customizing timers
for setting the pulse time width and the latency time between pulses. There are programmable thresholds for all three axes. The
pulse detection can be configured to run through the high-pass filter and also through a low-pass filter, which provides more
customizing and tunable pulse-detection schemes. The status register provides updates on the axes where the event was
detected and the direction of the tap. For more information on how to configure the device for pulse detection, please refer to
Freescale application note, AN4072.
5.8 Orientation Detection
The MMA8452Q has an orientation detection algorithm with the ability to detect all 6 orientations. The transition from portrait
to landscape is fixed with a 45° threshold angle and a ±14° hysteresis angle. This allows the for a smooth transition from portrait
to landscape at approximately 30° and then from landscape to portrait at approximately 60°.
The angle at which the dev ice no longer detect s the o rient ation change is r eferred to as the “Z-Lockout angle”. The device
operates down to 29° from the flat position. All angles are accurate to ±2°.
For further information on the orientation detection function refer to Freescale application note, AN4068.
Figure 8 shows the definitions of the trip angles going from Landscape to Portrait (A) and then also from Portrait to
Landscape (B).
MMA8452Q
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Freescale Semiconductor, Inc. 13
Figure 7. Landscape/Portrait Orientation
Top View
PU
Earth Gravity
Pin 1
Xout @ 0g
Yout @ -1g
Zout @ 0g
Xout @ 1g
Yout @ 0g
Zout @ 0g
Xout @ 0g
Yout @ 1g
Zout @ 0g
Xout @ -1g
Yout @ 0g
Zout @ 0g
LL
PD
LR
Side View
FRONT
Xout @ 0g
Yout @ 0g
Zout @ 1g
BACK
Xout @ 0g
Yout @ 0g
Zout @ -1g
Portrait
Landscape to Portrait
90°
Trip Angle = 60°
0° Landscape
Portrait
Portrait to Landscape
90°
Trip Angle = 30°
0° Landscape
(A) (B)
Upright
NORMAL
90°
Z-LOCK = 29°
0° Flat
DETECTION
REGION
LOCKOUT
REGION
Figure 8. Illustration of Landscape to Portrait Transition (A) and Portrait to Landscape Transition (B)
Figure 9 illustrates the Z-angle lockout region. When lifting the device upright from the flat position it will be active for
orientation detection as low as 29° from flat. .
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14 Freescale Semiconductor, Inc.
Figure 9. Illustration of Z-Tilt Angle Lockout Transition
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5.9 Interrupt Register Configurations
INTERRUPT
CONTROLLER
Data Ready
Motion/Freefall
Pulse
Orientation
Transient
Auto-SLEEP
INT ENABLE INT CFG
INT1
INT2
66
There are six configurable interrupts in the MMA8452Q: Data Ready, Motion/Freefall, Pulse, Orientation, Transient, and AutoSLEEP events. These six interrupt sources can be routed to one of two interrupt pins. The interrupt source must be enabled and
configured. If the event flag is asserted because the event condition is detected, the corresponding interrupt pin, INT1 or INT2,
will assert.
Figure 10. System Interrupt Generation Block Diagram
5.10 Serial I2C Interface
Acceleration data may be accessed through an I2C interface thus making the device particularly suit abl e for direct interfaci ng
with a microcontroller. The MMA8452Q features an interrupt signal which indicates when a new set of measured acceleration
data is available thus simplifying data synchronization in the digital system that uses the device. The MMA8452Q may also be
configured to generate other interrupt signals accordingly to the programmable embedded functions of the device for Motion,
Freefall, Transient, Orient a tion, and Pulse.
2
The registers embedded inside the MMA8452Q are accessed through the I
interface, VDDIO line must be tied high (i.e., to the interface supply voltage). If VDD is not present and VDDIO is present, the
MMA8452Q is in off mode and communications on the I2C interface are ignored. The I2C interface may be used for
communications between other I
2
C devices and the MMA8452Q does not affect the I2C bus.
Table 9. Serial Interface Pin Description
Pin Name Pin Description
SCL I
SDA I
SA0 I
There are two signals associated with the I
2
C Serial Clock
2
C Serial Data
2
C least significant bit of the device address
2
C bus; the Serial Clock Line (SCL) and the Serial Data line (SDA). The latter is a
bidirectional line used for sending and receiving the data to/from the interface. External pullup resistor s connected to VDDIO are
expected for SDA and SCL. When the bus is free both the lines are high. The I
and Normal mode (100 kHz) I
2
C standards (Table 5).
C serial interface (Table 9). To en able the I2C
2
C interface is compliant with fast mode (400 kHz),
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