MMA7331LCR1 [FREESCALE]
±4g, ±9g Three Axis Low-g Micromachined Accelerometer; ± 4G， ± 9克三轴低g加速度计微机械
| 型号： | MMA7331LCR1 |
| 厂家： | 
Freescale |
| 描述： | ±4g, ±9g Three Axis Low-g Micromachined Accelerometer |
| 文件： | 总11页 (文件大小：173K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Document Number: MMA7331LC
Rev 2, 6/2011
Freescale Semiconductor
Data Sheet: Technical Data
±4g, ±9g Three Axis Low-g
Micromachined Accelerometer
MMA7331LC
The MMA7331LC is a low power, low profile capacitive micromachined
accelerometer featuring signal conditioning, a 1-pole low pass filter,
temperature compensation, self test, and g-Select which allows for the
selection between 2 sensitivities. Zero-g offset and sensitivity are factory set
and require no external devices. The MMA7331LC includes a Sleep Mode in
which the device consumes extremely low current. This makes it ideal for
handheld battery powered electronics.
MMA7331LC: XYZ AXIS
ACCELEROMETER
4g, 9g
Features
•
•
•
•
•
•
•
•
•
•
•
•
3mm x 5mm x 1.0mm LGA-14 Package
Low Current Consumption: 400 μA
Sleep Mode: 3 μA
Low Voltage Operation: 2.2 V – 3.6 V
Selectable Sensitivity (±4g, ±9g)
Fast Turn On Time (0.5 ms Enable Response Time)
Self Test for Freefall Detect Diagnosis
Signal Conditioning with Low Pass Filter
Robust Design, High Shocks Survivability
RoHS Compliant
Bottom View
Environmentally Preferred Product
Low Cost
14 LEAD
LGA
CASE 1977-01
Typical Applications
•
•
•
•
•
•
•
•
3D Gaming: Tilt and Motion Sensing, Event Recorder
HDD MP3 Player: Freefall Detection
Top View
Laptop PC: Freefall Detection, Anti-Theft
Cell Phone: Image Stability, Text Scroll, Motion Dialing, E-Compass
Pedometer: Motion Sensing
N/C
PDA: Text Scroll
N/C
Self Test
N/C
Navigation and Dead Reckoning: E-Compass Tilt Compensation
Robotics: Motion Sensing
XOUT
YOUT
ZOUT
N/C
g-Select
ORDERING INFORMATION
VSS
VDD
N/C
N/C
Temperature
Range
Package
Drawing
Part Number
Package
Shipping
MMA7331LCT
MMA7331LCR1
MMA7331LCR2
-40 to +85°C
-40 to +85°C
-40 to +85°C
1977-01
1977-01
1977-01
LGA-14
LGA-14
LGA-14
Tray
7” Tape & Reel
13” Tape & Reel
Sleep
Figure 1. Pin Connections
© Freescale Semiconductor, Inc., 2011. All rights reserved.
VDD
g-Select
CLOCK
GEN
X-TEMP
COMP
OSCILLATOR
XOUT
YOUT
ZOUT
GAIN
+
FILTER
G-CELL
SENSOR
C to V
CONVERTER
Y-TEMP
COMP
Sleep
CONTROL LOGIC
NVM TRIM
Z-TEMP
COMP
SELFTEST
CIRCUITS
Self Test
VSS
Figure 2. Simplified Accelerometer Functional Block Diagram
Table 1. Maximum Ratings
(Maximum ratings are the limits to which the device can be exposed without causing permanent damage.)
Rating
Maximum Acceleration (all axis)
Symbol
Value
Unit
gmax
±5000
g
V
VDD
Ddrop
Tstg
–0.3 to +3.6
1.8
Supply Voltage
Drop Test(1)
m
°C
–40 to +125
Storage Temperature Range
1. Dropped onto concrete surface from any axis.
ELECTRO STATIC DISCHARGE (ESD)
WARNING: This device is sensitive to electrostatic
discharge.
Although the Freescale accelerometer contains internal
2000 V 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.
MMA7331LC
Sensors
2
Freescale Semiconductor
Table 2. Operating Characteristics
Unless otherwise noted: -40°C < TA < 85°C, 2.2 V < VDD < 3.6 V, Acceleration = 0g, Loaded output(1)
Characteristic
Symbol
Min
Typ
Max
Unit
Operating Range(2)
Supply Voltage(3)
Supply Current(4)
Supply Current at Sleep Mode(4)
Operating Temperature Range
Acceleration Range, X-Axis, Y-Axis, Z-Axis
g-Select: 0
VDD
IDD
IDD
TA
2.2
—
2.8
400
3
3.6
600
10
V
μA
μA
°C
—
-40
—
+85
gFS
gFS
—
—
±4
±9
—
—
g
g
g-Select: 1
Output Signal
Zero g (TA = 25°C, VDD = 2.8 V)(5), (6)
XY
VOFF
VOFF
1.316
1.45
-2
1.4
1.4
±0.5
-6.4
-0.9
0
1.484
1.484
2
V
Z
V
Zero g Temperature Coefficient(7)
TCO4g
TCO9g
TCO9g
TCO9g
mg/°C
mg/°C
mg/°C
mg/°C
X
-12
-0.6
5.2
Y
-7.9
-8.4
Z
8.5
Sensitivity (TA = 25°C, VDD = 2.8 V)
4g
S4g
S9g
289.5
75.2
308
83.6
326.5
91.9
mV/g
mV/g
%/°C
9g
Sensitivity(4)
S,TA
-0.0075
±0.002
+0.0075
Bandwidth Response
XY
f-3dBXY
f-3dBZ
ZO
—
—
24
400
300
32
—
—
40
Hz
Hz
kΩ
Z
Output Impedance
Self Test
Output Response
XOUT, YOUT
ZOUT
ΔgSTXY
ΔgSTZ
VIL
+0.05
+0.5
-0.1
+1.0
—
—
+1.2
g
g
Input Low
Input High
VSS
0.3 VDD
VDD
V
V
VIH
0.7 VDD
—
Noise
Power Spectral Density RMS (0.1 Hz – 1 kHz)(4)
nPSD
—
350
—
μg/
Hz
Control Timing
Power-Up Response Time(8)
Enable Response Time(9)
Self Test Response Time(10)
Sensing Element Resonant Frequency
XY
tRESPONSE
tENABLE
tST
—
—
—
1.0
0.5
2.0
2.0
2.0
5.0
ms
ms
ms
fGCELLXY
fGCELLZ
fCLK
—
—
—
6.0
3.4
11
—
—
—
kHz
kHz
kHz
Z
Internal Sampling Frequency
Output Stage Performance
Full-Scale Output Range (IOUT = 3 µA)
VFSO
VSS+0.1
-1.0
—
—
VDD–0.1
+1.0
V
Nonlinearity, XOUT, YOUT, ZOUT
Cross-Axis Sensitivity(11)
NLOUT
%FSO
VXY, XZ, YZ
-5.0
—
+5.0
%
1. For a loaded output, the measurements are observed after an RC filter consisting of an internal 32 kΩ resistor and an external 3.3 nF capacitor
(recommended as a minimum to filter clock noise) on the analog output for each axis and a 0.1 μF capacitor on V - GND. The output sensor
DD
3
bandwidth is determined by the Capacitor added on the output. f = 1/2π * (32 x 10 ) * C. C = 3.3 nF corresponds to BW = 1507 Hz, which is the minimum
to filter out internal clock noise.
2. These limits define the range of operation for which the part will meet specification.
3. Within the supply range of 2.2 and 3.6 V, the device operates as a fully calibrated linear accelerometer. Beyond these supply limits the device may
operate as a linear device but is not guaranteed to be in calibration.
4. This value is measured with g-Select in 4g mode.
5. The device can measure both + and – acceleration. With no input acceleration the output is at midsupply. For positive acceleration the output will
increase above V /2. For negative acceleration, the output will decrease below V /2.
DD
DD
6. For optimal 0g offset performance, adhere to AN3484 and AN3447.
7. X, Y, Z = 0g
8. The response time between 10% of full scale V input voltage and 90% of the final operating output voltage.
DD
9. The response time between 10% of full scale Sleep Mode input voltage and 90% of the final operating output voltage.
10. The response time between 10% of the full scale self test input voltage and 90% of the self test output voltage.
11. A measure of the device’s ability to reject an acceleration applied 90° from the true axis of sensitivity.
MMA7331LC
Sensors
Freescale Semiconductor
3
PRINCIPLE OF OPERATION
The Freescale accelerometer is a surface-micromachined g-Select
The g-Select feature allows for the selection between two
integrated-circuit accelerometer.
The device consists of a surface micromachined
capacitive sensing cell (g-cell) and a signal conditioning ASIC
contained in a single package. The sensing element is sealed
hermetically at the wafer level using a bulk micromachined
cap wafer.
The g-cell is a mechanical structure formed from
semiconductor materials (polysilicon) using semiconductor
processes (masking and etching). It can be modeled as a set
of beams attached to a movable central mass that move
between fixed beams. The movable beams can be deflected
from their rest position by subjecting the system to an
acceleration (Figure 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 acceleration.
sensitivities. Depending on the logic input placed on pin 10,
the device internal gain will be changed allowing it to function
with a 4g or 9g sensitivity (Table 3). This feature is ideal when
a product has applications requiring two different sensitivities
for optimum performance. The sensitivity can be changed at
anytime during the operation of the product. The g-Select pin
can be left unconnected for applications requiring only a 4g
sensitivity as the device has an internal pull-down to keep it
at that sensitivity (308 mV/g).
Table 3. g-Select Pin Description
g-Select
g-Range
Sensitivity
308 mV/g
83.6 mV/g
0
1
4g
9g
Sleep Mode
The 3-axis accelerometer provides a Sleep Mode that is
ideal for battery operated products. When Sleep Mode is
active, the device outputs are turned off, providing significant
reduction of operating current. A low input signal on pin 7
(Sleep Mode) will place the device in this mode and reduce
the current to 3 μA typ. For lower power consumption, it is
recommended to set g-Select to 4g mode. By placing a high
input signal on pin 7, the device will resume to normal mode
of operation.
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 dielectric constant, and D is the distance
between the beams.
The ASIC uses switched capacitor techniques to measure
the g-cell capacitors and extract the acceleration data from
the difference between the two capacitors. The ASIC also
signal conditions and filters (switched capacitor) the signal,
providing a high level output voltage that is ratiometric and
proportional to acceleration.
Filtering
The 3-axis accelerometer contains an onboard single-pole
switched capacitor filter. Because the filter is realized using
switched capacitor techniques, there is no requirement for
external passive components (resistors and capacitors) to set
the cut-off frequency.
Acceleration
Ratiometricity
Ratiometricity simply means the output offset voltage and
sensitivity will scale linearly with applied supply voltage. That
is, as supply voltage is increased, the sensitivity and offset
increase linearly; as supply voltage decreases, offset and
sensitivity decrease linearly. This is a key feature when
interfacing to a microcontroller or an A/D converter because
it provides system level cancellation of supply induced errors
in the analog to digital conversion process.
Figure 3. Simplified Transducer Physical Model
SPECIAL FEATURES
Self Test
The sensor provides a self test feature that allows the
verification of the mechanical and electrical integrity of the
accelerometer at any time before or after installation. This
feature is critical in applications such as hard disk drive
protection where system integrity must be ensured over the
life of the product. Customers can use self test to verify the
solderability to confirm that the part was mounted to the PCB
correctly. When the self test function is initiated, an
electrostatic force is applied to each axis to cause it to deflect.
The X- and Y-axis are deflected slightly while 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.
MMA7331LC
Sensors
4
Freescale Semiconductor
BASIC CONNECTIONS
PCB Layout
Pin Descriptions
Top View
POWER SUPPLY
N/C
VDD
N/C
Self Test
N/C
VRH
P0
VDD
VSS
C
C
VSS
C
XOUT
YOUT
ZOUT
Sleep
N/C
g-Select
Self Test
XOUT
P1
P2
g-Select
VSS
VDD
N/C
N/C
A/DIN
A/DIN
A/DIN
C
C
C
YOUT
ZOUT
Sleep
Figure 4. Pinout Description
Table 4. Pin Descriptions
Figure 6. Recommended PCB Layout for Interfacing
Accelerometer to Microcontroller
Pin No. Pin Name
Description
1
N/C
No internal connection
Leave unconnected
2
3
4
5
6
7
8
XOUT
YOUT
ZOUT
VSS
NOTES:
X direction output voltage
Y direction output voltage
Z direction output voltage
Power Supply Ground
1. Use 0.1 µF capacitor on VDD to decouple the power
source.
2. Physical coupling distance of the accelerometer to
the microcontroller should be minimal.
VDD
Power Supply Input
3. Place a ground plane beneath the accelerometer to
reduce noise, the ground plane should be attached to
all of the open ended terminals shown in Figure 6.
Logic input pin to enable product or Sleep Mode
Sleep
N/C
No internal connection
Leave unconnected
4. Use a 3.3 nF capacitor on the outputs of the
accelerometer to minimize clock noise (from the
switched capacitor filter circuit).
9
N/C
No internal connection
Leave unconnected
10
11
g-Select
N/C
Logic input pin to select g level
5. PCB layout of power and ground should not couple
power supply noise.
Unused for factory trim
Leave unconnected
12
N/C
6. Accelerometer and microcontroller should not be a
high current path.
Unused for factory trim
Leave unconnected
13
14
Self Test
N/C
Input pin to initiate Self Test
7. A/D sampling rate and any external power supply
switching frequency should be selected such that
they do not interfere with the internal accelerometer
sampling frequency (11 kHz for the sampling
frequency). This will prevent aliasing errors.
Unused for factory trim
Leave unconnected
10
Logic
Input
g-Select
8. 10 MΩ or higher is recommended on XOUT, YOUT and
2
X
ZOUT to prevent loss due to the voltage divider
OUT
13
Logic
Input
relationship between the internal 32 kΩ resistor and
the measurement input impedance.
Self Test
3.3 nF
3.3 nF
3.3 nF
V
DD
MMA7331LC
3
4
Y
6
OUT
V
V
DD
0.1 μF
5
7
SS
Z
OUT
Logic
Input
Sleep
Figure 5. Accelerometer with Recommended
Connection Diagram
MMA7331LC
Sensors
Freescale Semiconductor
5
DYNAMIC ACCELERATION
Top View
+Y
2
Side View
6
8
5
9
4
3
1
-X
+X
+Z
-Z
7
14
10 11 12 13
-Y
: Arrow indicates direction of package movement.
14-Pin LGA Package
STATIC ACCELERATION
Direction of Earth's gravity field.*
Top View
6
8
5
9
4
3
2
1
7
14
Side View
Top
10 11 12 13
X
Y
Z
@ 0g = 1.4 V
@ +1g = 1.708 V
@ 0g = 1.4 V
OUT
OUT
Bottom
X
Y
Z
@ 0g = 1.4 V
@ 0g = 1.4 V
@ +1g = 1.708 V
OUT
OUT
OUT
OUT
Bottom
13 12 11 10
9
5
8
6
Top
X
Y
Z
@ +1g = 1.708 V
@ 0g = 1.4 V
@ 0g = 1.4 V
X
Y
Z
@ -1g = 1.092 V
@ 0g = 1.4 V
@ 0g = 1.4 V
OUT
OUT
OUT
OUT
X
@ 0g = 1.4 V
@ 0g = 1.4 V
@ -1g = 1.708 V
OUT
OUT
14
7
Y
Z
OUT
OUT
OUT
1
2
3
4
X
Y
Z
@ 0g = 1.4 V
OUT
OUT
@ -1g = 1.092 V
@ 0g = 1.4 V
OUT
* When positioned as shown, the Earth’s gravity will result in a positive 1g output.
MMA7331LC
Sensors
Freescale Semiconductor
6
X-TCO mg/degC
X-TCS %/degC
LSL
Target
USL
LSL
Target
USL
USL
USL
-2
-1
0
1
1
1
2
-0.01
-0.005
0
.005
.005
.005
.01
.01
.01
Y-TCO mg/degC
Y-TCS %/degC
LSL
Target
USL
LSL
Target
-2
-1
0
2
-0.01
-0.005
0
Z-TCO mg/degC
Z-TCS %/degC
LSL
Target
USL
LSL
Target
-2
-1
0
2
-0.01
-0.005
0
Figure 7. MMA7331LC (4g only) Temperature Coefficient of Offset (TCO) and
Temperature Coefficient of Sensitivity (TCS) Distribution Charts
MMA7331LC
Sensors
Freescale Semiconductor
7
MINIMUM RECOMMENDED FOOTPRINT FOR SURFACE MOUNTED APPLICATIONS
PCB Mounting Recommendations
MEMS based sensors are sensitive to Printed Circuit
Board (PCB) reflow processes. For optimal zero-g offset after
PCB mounting, care must be taken to PCB layout and reflow
conditions. Reference application note AN3484 for best
practices to minimize the zero-g offset shift after PCB
mounting.
13
1
Surface mount board layout is a critical portion of the total
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.
10x0.8
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.
6x2
6
8
14x0.6
14x0.9
12x1
Figure 8. LGA 14-Lead, 5 x 3 mm Die Sensor
MMA7331LC
Sensors
Freescale Semiconductor
8
PACKAGE DIMENSIONS
CASE 1977-01
ISSUE A
14-LEAD LGA
MMA7331LC
Sensors
Freescale Semiconductor
9
PACKAGE DIMENSIONS
CASE 1977-01
ISSUE A
14-LEAD LGA
MMA7331LC
Sensors
10
Freescale Semiconductor
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MMA7331LC
Rev. 2
6/2011
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