MMA2301KEG
Rev 1, 11/2012
Freescale Semiconductor
Data Sheet: Technical Data
© 2009, 2012 Freescale Semiconductor, Inc. All rights reserved.
Surface Mount
Micromachined Accelerometer
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.
Features
• Integral Signal Conditioning
• Linear Output
• Ratiometric Performance
• 4th Order Bessel Filter Preserves Pulse Shape Integrity
• Calibrated Self-test
• Low Volt age Detect, Clock Monitor, and EPROM Parity Check Status
• Transducer Hermetically Sealed at Wafer Level for Superior Reliabi lity
• Robust Design, High Shocks Survivability
• Robust Design, High Shock Survivability
• Qualified AEC-Q100, Rev. F Grade 2 (-40C/ +105C)
Typical Applicat ions
• Vibration Monitoring and Recording
• Impact Monitoring
ORDERING INFORMATION
Device Name Temperature Range Case No. Package
MMA2301EG –40to 125C475-01 SOIC-16
MMA2301EGR2 –40to 125C475-01 SOIC-16, Tape & Reel
MMA2301KEG* –40to 125C475-01 SOIC-16
MMA2301KEGR2* –40to 125C475-01 SOIC-16, Ta pe & Reel
*Part number sourced from a different facility.
MMA2301KEG
MMA2301KEG: X-AXIS SENSITIVITY
MICROMACHINED
ACCELEROMETER
±200g
KEG SUFFIX (Pb-FREE)
16-LEAD SOIC
CASE 475-01
G-Cell
Sensor Integrator Gain Filter Temp
Self-Test Control Logic and
EPROM Trim Circuits Clock
Generator
Oscillator
VDD
VOUT
VSS
ST
STATUS
Figure 1. Simplified Accelerometer Functional Block Diagram
N/C
N/C
N/C
ST
VOUT
STATUS
VSS
VDD
N/C
N/C
N/C
N/C
N/C
N/C
N/C
N/C
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
Figure 2. Pin Connections
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MMA2301KEG
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.
Table 1. Maximum Ratings
(Maximum ratings are the limits to which the device can be exposed without causing permanent damage.)
Rating Symbol Value Unit
Powered Acceleration (all axes) Gpd 1500 g
Unpowered Acceleration (all axes) Gupd 2000 g
Supply Voltage VDD –0.3 to +7.0 V
Drop Test(1)
1. Dropped onto concrete surface from any axis.
Ddrop 1.2 m
Storage Temperature Range Tstg –40 to +125 °C
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Table 2. Operating Characteristics
(Unless otherwise noted: -40C TA +105C, 4.75 VDD 5.25, Acceleration = 0g, Loaded output)(1)
1. For a loaded out put the measur ements are observed after an RC filter consisting of a 1 k resistor and a 0.01 F capacitor to ground.
Characteristic Symbol Min Typ Max Unit
Operating Range(2)
Supply Voltage(3)
Supply Current
Operating Temperature Range
Acceleration Range
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.
VDD
IDD
TA
gFS
4.75
3.0
-40
—
5.0
—
—
225
5.25
6.0
+125
—
V
mA
C
g
Output Signal
Zero g (TA = 25C, VDD = 5.0 V)(4)
Zero g
Sensitivity (TA = 25C, VDD = 5.0 V)(5)
Sensitivity
Bandwidth Response
Nonlinearity
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 V DD/2.
5. The device is calibrated at 35g.
VOFF
VOFF,V
S
SV
f-3dB
NLOUT
2.4
0.46 VDD
9.5
1.86
360
-1.0
2.5
0.50 VDD
10.0
2.0
400
—
2.6
0.54 VDD
10.5
2.14
440
1.0
V
V
mV/g
mV/g/V
Hz
% FSO
Noise
RMS (.01-1 kHz)
Power Spectral Density
Clock Noise (without RC load on output)(6)
6. At clock frequency 70 kHz.
nRMS
nPSD
nCLK
—
—
—
—
110
2.0
2.8
—
—
mVrms
V/(Hz1/2)
mVpk
Self-Test
Output Response(7)
Input Low
Input High
Input Loading(8)
Response Time(9)
7. VOFF calculated with typical sensitivity.
8. The digital input pin has an internal pull-down current source to prevent inadvertent self test initiation due to external board level leakages.
9. Time for the output to reach 90% of its final value after a self-test is initiated.
gST
VIL
VIH
IIN
tST
24
VSS
0.7 x VDD
-30
—
30
—
—
-100
2.0
36
0.3 x VDD
VDD
-260
10
g
V
V
A
ms
Status(10) (11)
Output Low (Iload = 100 A)
Output High (Iload = 100 A)
10. 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.
11. The S t atus 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.
VOL
VOH
—
VDD -0.8 —
—0.4
—V
V
Minimum Supply Voltage (LVD Trip) VLVD 2.7 3.25 4.0 V
Clock Monitor Fail Detection Frequency fmin 50 — 260 kHz
Output Stage Performance
Electrical Saturation Recovery Time(12)
Full Scale Output Range (IOUT = 200 A)
Capacitive Load Drive(13)
Output Impedance
12. Time for amplifiers to recover after an acceleration signal causing them t o saturate.
13. Preserves phase margin (60) to guarantee output amplifier stability.
tDELAY
VFSO
CL
ZO
—
0.25
—
—
0.2
—
—
300
—
VDD -0.25
100
—
ms
V
pF
Mechanical Characteristics
Transverse Sensitivity(14)
Package Resonance
14. A measure of the device's ability to reject an acceleration applied 90 from the true axis of sensitivity.
VXZ,YZ
fPKG
—
——
10 5.0
—% FSO
kHz
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MMA2301KEG
PRINCIPLE OF OPERATION
The Freescal e accelerometer is a s urface-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 semiconducto r
processes (masking and etching). It can be modeled as two
stationary plates with a moveable plate in-between. The
center plate can be deflected from its rest position by
subjecting the system to an acceleration (Figure 3).
When the center plate deflects, the distance from it to one
fixed plate will increase by the same amount that the distance
to the other plate decreases. The change in distance is a
measure of acceleration.
The g-cell plates form two back-to-back capacitors
(Figure 4). As the center plate moves with acceleration, the
distance between the plates changes and each capacitor's
value will change, (C = A/D). Where A is the area of the
plate, is the dielectric constant, and D is the distance
between the pla tes.
The CMOS ASIC uses switched capacitor techniques to
measure the g - cel l capacitors and extract the acc el e ra ti on
data from the difference between the two capacitors. The
ASIC also signal conditio ns and filters (switched capacitor)
the signal, providing a high level outp ut voltage that is
ratiometric and proportional to acceleration.
SPECIAL FEATURES
Filtering
The Freescale accelerometers contain an onboard 2-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.
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 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 moveabl e plate. The resulting electrostatic
force 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 fu nctioning.
Status
Freescale accelerometers include fault detection circuitry
and a fault latch. The Status pin is an outp ut from the fault
latch, OR'd with self-test, and is set high whenever the
following event occurs:
• 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.
Acceleration
Figure 3. Transduc er Physical Model an d
Equivalent Circuit Model
Fe1
2
---AV2
d2
------=
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MMA2301KEG
BASIC CONNECTIONS
PINOUT DESCRIPTION
Figure 4. SOIC Accelerometer with Recommended
Connection Diagram
Figure 5. Recommend PCB Layout for Interfacing
Accelerometer to Microcontroller
NOTES:
• Use a 0.1 F capacitor on VDD to decouple the power
source.
• Physical coupling distance of the accelerometer to the
microcontro l l er 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 termi nals shown in Figure 5
• Use an RC filter of 1 k and 0.01 F 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.
• Accelerometer and microcontroller should not be a high
current path.
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 .
This will prevent aliasing errors.
Table 3. Pin Descriptions
Pin No. Pin Name Description
1 thru 3 N/C Leave unconnected.
4 ST Logic input pin used to initiate self-
test.
5V
OUT Output voltage of the accelerometer.
6 STATUS Logic output pin to indicate fault.
7V
SS The power supply ground.
8V
DD The power supply input.
9 thru 13 Trim pins Used for factory trim. Leave
unconnected.
14 thru 16 — No internal connection. Leave
unconnected.
10
11
12
13
14
15
16
9
N/C
N/C
N/C
N/C
N/C
N/C
N/C
N/C
8
7
6
5
4
3
2
1
N/C
N/C
N/C
ST
VOUT
STATUS
VDD
VSS
MMA2301KEG
ST
VDD
VSS
VOUT Output
Signal
R1
1 k
5
C2
0.01 F
4
8
7
Logic
Input
VDD
C1
0.1 F
6Status
P0
A/D In
VRH
VSS
VDD
ST
VOUT
VSS
VDD
0.01 F
1 k
0.1 F
Power Supply
C
0.1 F
P1
STATUS
Microcontroller
Accelerometer
C
C
C
0.1 F
PCB Layout
R
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MMA2301KEG
* When positioned as shown, the Earth's gravity will result in a positive 1g output.
Dynamic Acceleration Sensing Direction
10 11 12 13 14 15 16
87654321
9
Direction of Earth's gravity field.*
Front View Side View
Static Acceleration Sensing Direction
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
x
x
16-Pin SOIC Package
N/C pins are recommended to be left FLOATING
Top View
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.
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MMA2301KEG
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 bridgi ng and
shorting between solder pads.
Figure 6. Footprint SOIC-16 (Case 475-01)
0.380 in.
9.65 mm
0.050 in.
1.27 mm
0.024 in.
0.610 mm
0.080 in.
2.03 mm
MMA2301KEG
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PACKAGE DIMENSIONS
CASE 475-01
ISSUE C
16-LEAD SOIC
PAGE 1 OF 2
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MMA2301KEG
PACKAGE DIMENSIONS
CASE 475-01
ISSUE C
16-LEAD SOIC
PAGE 2 OF 2
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MMA2301KEG
Table 4. Revision History
Revision
number Revision
date Description of changes
1 11/2012 • Tab le 2. Operating Characteristics, added footnote f or Self-Test Output Response, updated page
4: Princip le of Operation
MMA2301KEG
Rev. 1
11/2012
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