MMA2301D [FREESCALE]
Surface Mount Micromachined Accelerometer; 表面贴装微机械加速度计
| 型号： | MMA2301D |
| 厂家： | 
Freescale |
| 描述： | Surface Mount Micromachined Accelerometer |
| 文件： | 总10页 (文件大小：273K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MMA2301D
Rev 4, 03/2006
Freescale Semiconductor
Technical Data
Surface Mount
Micromachined Accelerometer
MMA2301
The MMA series of silicon capacitive, micromachined accelerometers feature
signal conditioning, a 4-pole low pass filter and temperature compensation.
Zero-g offset full scale span and filter cut-off are factory set and require no
external devices. A full system self-test capability verifies system functionality.
MMA2301D: X-AXIS SENSITIVITY
MICROMACHINED
ACCELEROMETER
±200G
Features
•
•
•
•
•
•
•
•
Integral Signal Conditioning
Linear Output
Ratiometric Performance
4th Order Bessel Filter Preserves Pulse Shape Integrity
Calibrated Self-test
Low Voltage Detect, Clock Monitor, and EPROM Parity Check Status
Transducer Hermetically Sealed at Wafer Level for Superior Reliability
Robust Design, High Shocks Survivability
Typical Applications
•
•
Vibration Monitoring and Recording
Impact Monitoring
D SUFFIX
EG SUFFIX (Pb-FREE)
16-LEAD SOIC
CASE 475-01
ORDERING INFORMATION
Device Name
MMA2301D
Temperature Range
–40° to 125°C
Case No.
475-01
475-01
475-01
475-01
Package
SOIC-16
MMA2301DR2
MMA2301EG
MMA2301EGR2
–40° to 125°C
SOIC16, Tape & Reel
SOIC-16
–40° to 125°C
–40° to 125°C
SOIC16, Tape & Reel
VDD
G-Cell
Sensor
Temp
VOUT
N/C
N/C
N/C
ST
16
15
14
13
12
11
10
9
N/C
N/C
N/C
N/C
N/C
N/C
N/C
N/C
Integrator
Gain
Filter
1
2
3
4
5
6
7
8
ST
Control Logic and
EPROM Trim Circuits
VOUT
Clock
Generator
Oscillator
Self-Test
STATUS
VSS
VSS
VDD
STATUS
Figure 2. Pin Connections
Figure 1. Simplified Accelerometer Functional Block Diagram
© Freescale Semiconductor, Inc., 2006. All rights reserved.
Table 1. Maximum Ratings
(Maximum ratings are the limits to which the device can be exposed without causing permanent damage.)
Rating
Powered Acceleration (all axes)
Symbol
Gpd
Value
1500
Unit
g
Unpowered Acceleration (all axes)
Supply Voltage
Gupd
VDD
2000
g
–0.3 to +7.0
1.2
V
Drop Test(1)
Ddrop
Tstg
m
Storage Temperature Range
1. Dropped onto concrete surface from any axis.
–40 to +125
°C
ELECTRO STATIC DISCHARGE (ESD)
WARNING: This device is sensitive to electrostatic
discharge.
Although the accelerometers contain internal 2 kV 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.
MMA2301D
Sensors
2
Freescale Semiconductor
Table 2. Operating Characteristics
(Unless otherwise noted: -40°C ≤ TA ≤ +105°C, 4.75 ≤ VDD ≤ 5.25, Acceleration = 0g, Loaded output)(1)
Characteristic
Symbol
Min
Typ
Max
Unit
Operating Range(2)
Supply Voltage(3)
Supply Current
VDD
IDD
TA
4.75
3.0
-40
—
5.0
—
—
5.25
6.0
+125
—
V
mA
°C
g
Operating Temperature Range
Acceleration Range
gFS
225
Output Signal
Zero g (TA = 25°C, VDD = 5.0 V)(4)
Zero g
VOFF
VOFF,V
S
SV
f-3dB
NLOUT
2.4
0.46 VDD
9.5
1.86
360
2.5
0.50 VDD
10.0
2.0
400
—
2.6
0.54 VDD
10.5
2.14
440
V
V
Sensitivity (TA = 25°C, VDD = 5.0 V)(5)
Sensitivity
mV/g
mV/g/V
Hz
Bandwidth Response
Nonlinearity
-1.0
1.0
% FSO
Noise
RMS (.01-1 kHz)
Power Spectral Density
Clock Noise (without RC load on output)(6)
nRMS
nPSD
nCLK
—
—
—
—
110
2.0
2.8
—
—
mVrms
µV/(Hz1/2
mVpk
)
Self-Test
Output Response
Input Low
gST
VIL
VIH
IIN
24
VSS
0.7 x VDD
-30
30
—
—
-100
2.0
36
0.3 x VDD
VDD
-260
10
g
V
V
µA
ms
Input High
Input Loading(7)
Response Time(8)
tST
—
Status(9) (10)
Output Low (Iload = 100 µA)
Output High (Iload = 100 µA)
VOL
VOH
—
DD -0.8
—
—
0.4
—
V
V
V
Minimum Supply Voltage (LVD Trip)
Clock Monitor Fail Detection Frequency
VLVD
fmin
2.7
3.25
—
4.0
V
50
260
kHz
Output Stage Performance
Electrical Saturation Recovery Time(11)
Full Scale Output Range (IOUT = 200 µA)
Capacitive Load Drive(12)
tDELAY
VFSO
CL
—
0.25
—
0.2
—
—
—
DD -0.25
100
ms
V
pF
Ω
V
Output Impedance
ZO
—
300
—
Mechanical Characteristics
Transverse Sensitivity(13)
Package Resonance
VXZ,YZ
fPKG
—
—
—
10
5.0
—
% FSO
kHz
1. For a loaded output the measurements are observed after an RC filter consisting of a 1 kΩ resistor and a 0.01 µF capacitor to ground.
2. These limits define the range of operation for which the part will meet specification.
3. Within the supply range of 4.75 and 5.25 volts, 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. The device can measure both + and - acceleration. With no input acceleration the output is at midsupply. For positive acceleration the output
will increase above VDD/2 and for negative acceleration the output will decrease below VDD/2.
5. The device is calibrated at 35g.
6. At clock frequency ≅ 70 kHz.
7. The digital input pin has an internal pull-down current source to prevent inadvertent self test initiation due to external board level leakages.
8. Time for the output to reach 90% of its final value after a self-test is initiated.
9. The Status pin output is not valid following power-up until at least one rising edge has been applied to the self-test pin. The Status pin is
high whenever the self-test input is high, as a means to check the connectivity of the self-test and Status pins in the application.
10. The Status pin output latches high if a Low Voltage Detection or Clock Frequency failure occurs, or the EPROM parity changes to odd. The
Status pin can be reset low if the self-test pin is pulsed with a high input for at least 100 us, unless a fault condition continues to exist.
11. Time for amplifiers to recover after an acceleration signal causing them to saturate.
12. Preserves phase margin (60°) to guarantee output amplifier stability.
13. A measure of the device's ability to reject an acceleration applied 90° from the true axis of sensitivity.
MMA2301D
Sensors
Freescale Semiconductor
3
PRINCIPLE OF OPERATION
The Freescale Semiconductor, Inc. accelerometer is a
facing side of the beam, ε is the dielectric constant, D is the
distance between the beams, and N is the number of beams.
The CMOS 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.
surface-micromachined integrated-circuit accelerometer.
The device consists of a surface micromachined
capacitive sensing cell (g-cell) and a CMOS signal
conditioning ASIC contained in a single integrated circuit
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).
Acceleration
As the beams attached to the central mass move, the
distance from them to the fixed beams on one side will
increase by the same amount that the distance to the fixed
beams on the other side decreases. The change in distance
is a measure of acceleration.
The g-cell plates form two back-to-back capacitors
(Figure 3). As the central mass moves with acceleration, the
distance between the beams change and each capacitor's
value will change, (C = NAε/D). Where A is the area of the
Figure 3. Simplified Transducer Physical Model versus
Transducer Physical Model
SPECIAL FEATURES
Filtering
Ratiometricity
The accelerometers contain an onboard 4-pole switched
capacitor filter. A Bessel implementation is used because it
provides a maximally flat delay response (linear phase) thus
preserving pulse shape integrity. 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.
Ratiometricity simply means that the output offset voltage
and sensitivity will scale linearly with applied supply voltage.
That is, as you increase supply voltage 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.
Self-Test
Status
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 automotive airbag
systems where system integrity must be ensured over the life
of the vehicle. A fourth plate is used in the g-cell as a self-test
plate. When the user applies a logic high input to the self-test
pin, a calibrated potential is applied across the self-test plate
and the moveable plate. The resulting electrostatic force
(Fe = 1/2 AV2/d2) causes the center plate to deflect. The
resultant deflection is measured by the accelerometer's
control ASIC and a proportional output voltage results. This
procedure assures that both the mechanical (g-cell) and
electronic sections of the accelerometer are functioning.
Freescale accelerometers include fault detection circuitry
and a fault latch. The Status pin is an output from the fault
latch, OR'd with self-test, and is set high whenever one (or
more) of the following events occur:
•
•
•
Supply voltage falls below the Low Voltage Detect (LVD)
voltage threshold
Clock oscillator falls below the clock monitor minimum
frequency
Parity of the EPROM bits becomes odd in number.
The fault latch can be reset by a rising edge on the self-test
input pin, unless one (or more) of the fault conditions
continues to exist.
MMA2301D
Sensors
Freescale Semiconductor
4
BASIC CONNECTIONS
PINOUT DESCRIPTION
PCB Layout
STATUS
16
15
14
13
12
11
10
9
N/C
N/C
N/C
N/C
N/C
N/C
N/C
N/C
N/C
N/C
N/C
ST
1
2
3
4
5
6
7
P1
ST
P0
VOUT
VSS
VOUT
VSS
A/D In
R
STATUS
VSS
0.1 µF
C
C
0.01 µF
0.1 µF
1 kΩ
0.1 µF
VDD
VDD
8
C
VDD
VRH
C
Table 3. Pin Descriptions
Pin No.
1 thru 3
4
Pin Name
N/C
Description
Leave unconnected.
Power Supply
ST
Logic input pin used to initiate self-
test.
Figure 5. Recommend PCB Layout for Interfacing
Accelerometer to Microcontroller
5
VOUT
Output voltage of the accelerometer.
NOTES:
•
•
•
Use a 0.1 µF capacitor on VDD to decouple the power
source.
6
STATUS Logic output pin to indicate fault.
7
8
VSS
VDD
The power supply ground.
The power supply input.
Physical coupling distance of the accelerometer to the
microcontroller should be minimal.
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 5
9 thru 13
Trim pins Used for factory trim. Leave
unconnected.
14 thru 16
—
No internal connection. Leave
unconnected.
•
Use an RC filter of 1 kΩ and 0.01 µF on the output of the
accelerometer to minimize clock noise (from the switched
capacitor filter circuit).
•
•
PCB layout of power and ground should not couple power
supply noise.
6
Accelerometer and microcontroller should not be a high
current path.
MMA2301D
VDD
Status
Logic
Input
4
8
ST
VDD
R1
1 kΩ
A/D sampling rate and any external power supply
5
Output
Signal
VOUT
switching frequency should be selected such that they do not
interfere with the internal accelerometer sampling frequency.
This will prevent aliasing errors.
C1
0.1 µF
C2
0.01 µF
7
VSS
Figure 4. SOIC Accelerometer with Recommended
Connection Diagram
MMA2301D
Sensors
Freescale Semiconductor
5
Dynamic Acceleration Sensing Direction
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
Acceleration of the package
in the +X direction (center
plate moves in the -X
direction) will result in an
increase in the output.
Activation of Self Test
moves the center plate in
the −X direction, resulting in
an increase in the output.
+x
−x
16-Pin SOIC Package
N/C pins are recommended to be left FLOATING
Top View
Static Acceleration Sensing Direction
8
7
6
5
4
3
2 1
Direction of Earth's gravity field.*
9
10 11 12 13 14 15 16
Front View
Side View
* When positioned as shown, the Earth's gravity will result in a positive 1g output.
MMA2301D
Sensors
6
Freescale Semiconductor
MINIMUM RECOMMENDED FOOTPRINT FOR SURFACE MOUNTED APPLICATIONS
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. 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.
0.050 in.
1.27 mm
0.380 in.
9.65 mm
0.024 in.
0.610 mm
0.080 in.
2.03 mm
Figure 6. Footprint SOIC-16 (Case 475-01)
MMA2301D
Sensors
Freescale Semiconductor
7
PACKAGE DIMENSIONS
PAGE 1 OF 2
CASE 475-01
ISSUE C
16-LEAD SOIC
MMA2301D
Sensors
Freescale Semiconductor
8
PACKAGE DIMENSIONS
PAGE 2 OF 2
CASE 475-01
ISSUE C
16-LEAD SOIC
MMA2301D
Sensors
Freescale Semiconductor
9
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MMA2301D
Rev. 4
03/2006
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